The Borg Warner 9 Bolt Rearend is actually called the M78 Rearend or "78 series". It has been made since the late 60's in Australia by a company called BTR Engineering Ltd. BTR was bought out by Borg-Warner under which company name the rears were produced for our cars. In the last few years Borg-Warner was bought out by Dana Corp. and the rears are still produced by Dana today in the same BTR factory under the "Spicer Axles Australia" name. www.spiceraxle.com.au/products.htm#srd


The rear is offically rated @ 220 kW = 295 HP
@ 435 Nm = 320 lb/ft
It can support a GVW of 2740 kg = 6041 lbs

The above ratings seem to be a bit conservative, as one member I know of has one that has survived the abuse of a 500hp/500+ lb/ft Big Block for a few years now. The 9 bolt offers a few advantages over a 7.625" 10 Bolt: 4 pinion spider gear design, shorter distance between carrier bearing caps, and a 7.75" ring gear diameter adds strength.
All 9 bolt rears for f-bodies use 28 spline axles.
Another advantage over the 10 bolt is it uses pressed on tapered axle bearings allowing the axles to be bolted in instead of using c-clips. I've heard several people say the 9bolt is stronger than the Dana 44. I do not believe this because in my many years of research, I've never seen one shred of FACT to support it. The dana 44 uses bolt in axles and has a larger 8.5" dia. ring gear versus the 9 bolts 7.75" dia. ring gear. Most, if not all Posi Dana 44's built for camaro's were 4 pinion versions also. Dana 44's were used by GM as service/warranty replacements for problematic 9 and 10 bolt rears, then offered them thru GM Performance Parts, and they were then used on the 91-92 firehawks if that tells you anything.

85-90 9 bolt equipped f-bodies were available with either standard open differentials or limited slip versions as well as several different ratios including: 2.77, 3.08, 3.27 (G92 w/auto), 3.45 (G92 w/stick), and a few 3.70 ratio's came in some 85 & 86 Firebird's w/ RPO Option Codes L69 (305 "High Output" Carb Engine), 5 speed trans, & G92 =Very Rare!

3.27 and numerically higher gears will not fit on 3.08 and numerically down carriers. If you have a 2.77 or 3.08 rear and want 3.27 or higher you will have to get a 3 series carrier. www.9bolt.com.

The "Limited Slip" or "posi" rears used on f-bodies used what is called the "Seperated Cone Slip Resistant Differential".
They also make a better version called the Hydratrak SRD but it uses a different spline count on the axles preventing it from being a direct swap into our rears

Vehicles originally equipped with the 9 bolt rear:
Australian made cars: Certain models of Ford Falcons since 1971, Holden Commodores from 1986 thru 1991, Chrysler Valiants since 1971, certain Aussie made Toyota Corrollas & Coronas, Nissan R31 Skylines/Pintaras & certian Datsun's, Mitsubishi Sigmas, Leyland P76s ...1997-up Morgan Plus 8s have the Hydratrak version. In the UK the rears were used on certain Vauxhall models and Jensen-Healey's.

I've also heard that Ford uses the 9 bolt center section in their Escapes and Mazda Tributes, but I haven't verified it yet.

The Nissan Austraila PN for 3.9 gears is 38100-J7100

3.7 gears were used in R31 Skylines with manual trans, the PN for those gears is 38100-J7110

4.1 gears were used in R31 Pintara's (manual or auto) and the PN is 38100-J7000

Holden's and Fords got nothing shorter than 3.45 gears AFAIK.


In 1998 the Australian magazine "Street Machine" did a series of articles on this rear axle, Another member has posted it somewhere in the thread below.

 

Here is some info on checking and tightening them up by using shims. This info is from a post originally done by Karl Hunter and info provided by Miles from 9bolt.com.
The posi units of 9 bolts will wear. One of the most common reasons a 9 bolt fails is due to excessive backlash between the ring gear and pinion (usually due to worn out pinion bearings or improper pinion preload) or between the side gear and the pinion gears (usually due to worn out brake (ie posi) cones). Either of these usually results in broken gear teeth.

TESTING THE POSI
1. Place transmission in Park (or low gear for manual transmission).
2. Raise rear tires from the ground.
3. Lock one wheel from rotating.
4. Measure torque required to rotate opposite wheel.
5. If torque is less than 35 lb ft unit should be replaced or rebuilt.

CARRIER SHIMMING
First you need to find shims. There is no G.M. part for this, you just have to use whatever is available.

You need a variety of thickness of shims ranging from .010" to .050" in .005" increments. Some types of differential pinion bearing shims will work for this purpose, but use ones with a Max Outside Diameter of 2.5" and a Min Inside diameter of 1.5"

Mount one axle in a LARGE bench vise with splined end pointing straight up. The vise must be securely mounted to a strong table or work bench.
Place the differential carrier over the splined end of the axle with the ring gear teeth facing downwards.
Mark the 2 halves of the housing for alignment during re-assembly.
Loosen the bolts that hold the housing together. (the ones with the 7/16" head) It is not necessary to remove the ring gear, however if it is to be removed it should be marked prior to disassembly for proper re-alignment.
Once all the bolts holding the housing together have been fully loosened remove the upper carrier housing from the assembly. All the internal parts for the differential are now accessible. Each half of the carrier houses a friction cone and a side gear. All parts must be kept in order. Place match marks on the cross shaft and spider gears prior to removal. There should also be a spring pack in the centre of the assembly, which should have 3 springs together. G.M. recommends replacing these springs anytime the differential is apart, but if they are not broken this should not be necessary. If any other parts are broken it is recommended to find a complete replacement for the carrier, however single parts such as side gears or spider gears may be replaced individually in emergency situations. If a friction cone is worn to the point where the end of the cone is contacting the housing at the inner most point (it will be evident by the wear pattern) then the carrier must be replaced.
Place the friction cone in its respective half of the housing and insert a shim between the side gear and the cone. Place the cross shaft with spider gears on top of the cone and gear in the housing. If the cross shaft seats fully into the housing and there is play between the spider gears and the side gear then use a larger shim. The idea is to remove all play in the gears while still allowing the cross shaft to seat fully in the housing. If too big a shim is used then the cross shaft will not seat properly and the assembly will bind causing the differential to act like a spool or possibly cause premature failure.

Install brake cones in the differential case. Measure the distance from differential case mating surface to flat surface on brake cone when it is fully seated. This is done to determine the size brake cone shim required.

Distance Measured In.(mm) Shim Size In.(mm)
1.155-1.162 (29.34-29.51) No shim required
1.163-1.167 (29.54-29.64) .005 (.13)
1.168-1.172 (29.67-29.77) .010 (.25)

ADVANCED SETUP- SOFT FEEL shim each side until all play is removed and cross shaft seats properly in case, then remove .005 to .010 inch of shim.

ADVANCED SETUP- HARD FEEL shim each side until all play is removed and cross shaft seats properly in case and add up to BUT NO MORE THAN .005" of shim per side. This will provide additional preload to the differential that is not possible unless the gears themselves are loaded. RECOMMENDED FOR RACE USE ONLY. If the vehicle is to be street driven on a regular basis it is not recommended to preload the gears.

The optimal amount of shim for Street-Race use is the point where all play is removed from the side gears and the cross shaft and spider gears seat properly in the housing. All one wheel peel will be eliminated and the differential will still operate normally.

RE-ASSEMBLY (This part is easier with 2 people)
Place components into case half without ring gear and place onto axle mounted in vise. It is important to re-assemble the case using the axles to align the internal components, otherwise the splines on the side gear and the friction cone may not be aligned and it will be impossible to insert the axle when the case is tightened.
Place cross shaft with spider gears into lower half of case and insert preload springs and spring plates.
Place other side gear on top of spider gears, then place the correct shim on top of the side gear then place the friction cone on top. All components should now be in place and in correct alignment. Double check to make sure there are no left over parts.
Place other case half over the assembly. Make sure the alignment marks line up.
Insert all bolts and hand tighten. The case may not seem to go together at this point, don't worry, the preload springs have not been compressed yet.
Insert other axle shaft into upper case half and align friction cone and side gear. Do not remove axle shafts until carrier is re-torqued.
Tighten bolts little by little in a cross-pattern until the 2 case halves seat together then torque to 29 Lb.Ft.
Remove axle from upper case half (you may have to hammer it out) and remove carrier from axle mounted in vise.
Re-install carrier into housing making sure all parts are re-installed in original order. It will be a tight fit, one side bearing shim will have to be GENTLY tapped into place with a hammer, preferably a brass faced, or use a brass drift. Install all components except one side gear shim, then do the remaining side gear shim last and gently tap it into place.
Install bearing caps in original positions and torque to 40 Lb.Ft.
Install axles. They may need some persuasion with a hammer to fully seat. Tighten axle retainer bolts to 36 Lb.Ft. Don't forget the caliper mounting plates.

 

TORQUE SPECS:
Pinion Bearing Preload-Inch Lbs. NEW 12-15 USED 6-7
Ring Gear Bolts-Ft Lbs. 65
Bearing Cap Bolts-Ft Lbs. 45
Axle Retainer Bolts-Ft Lbs. 36
Rear Cover Bolts-Ft Lbs. 25
Carrier Half Bolts-Ft Lbs. 29

Fluid Capacity with stock cover 1.7 qts

Backlash-.006-.010 inch

One of the most common reasons a 9 bolt fails is due to excessive backlash between the ring gear and pinion (usually due to worn out pinion bearings or improper pinion preload) or between the side gear and the pinion gears (usually due to worn out brake (ie posi) cones). Either of these usually results in broken gear teeth.

Set up the gear sets with a little more toe pattern and on the low side for backlash (preferrably between .006-.008). This is a little stronger, but also makes more noise. Also, if the backlash is set too low
the gears will bind up when hot.

Here's a link to Slow89Iroc-Z's post on his setup experience AND the exploded views and pn's of the 9bolt rear from the GM parts catalogs:
https://www.thirdgen.org/techbb2/sho...hreadid=239424

 

RATECH www.ratechmfg.com/gmstandard.htm
Great source for individual parts.
Pinion Shims 1104*
Severe Duty Pinion Shims 1133*
Carrier Shims 1105
Crush Sleeve 3101^
Solid Pinion Spacer 4114^ (Replaces 3101)
Smart Sleeve 11004^ (Replaces 3101 or 4114)
Pinion Seal 6120
Pinion Nut 1508
RG Bolts 1303*
Gasket 5124
Inner Pinion Bearing? Check yours and then check with ratech-they list 3 different ones for some reason
Outer Pinion Bearing 8001*
Install Kit (w/o bearings) 130K
* Denotes same as 7.625" 10 Bolt
^ Denotes same as Ford 8" & Dana 35

Reider Racing/Precision Gear- http://www.reiderracing.com/home.htm
Best price I've found for an overhaul kit.
They also sell 3.70 Gears

US Gear/Strange 3.70 Ring/Pinion Set Part # 01-878370BW sometimes you can find one somewhere cheap on clearance.

Auto Zone has the cheapest price on Timken Axle Bearings (Part # Set-9). You'll need to replace the seals also, I recommend Timken 710179 for the passenger side and 224255 for the driver's side.
They also sell Timken pinion seals part # 7457N. I've never found them cheaper anywhere else.

Randy's Ring and Pinion sells Yukon Brand 3.70 gears and install or overhaul kits. They are the best price for them with an overhaul kit and new axle bearings and seals you'll find, but I hear the overhaul kit has some mismatched parts.
Ratech or Reider have competitive prices on their overhaul kits and their parts are all top quality including Timken Bearings and Seals.

Larry Burd larryburd@mail.com sells shims to tighten your posi.

And lastly,www.9bolt.com - The only vendor here in the US that I know of who sells ratio's other than 3.70. Somehow he's got a hookup in Australia and can get the OEM Holden/Ford stuff imported.
He offers used sets from time to time and offers new 3.27, 3.45, 3.73. 3.91, and 4.10 ratios. They're high, but they're OEM parts. He also offers new 3 series carriers. And new internal parts for the LSD unit such as cones, spider gears, and cross shafts.

If you desperately need small parts for inside the posi carrier and can't find them locally you may try Dick Craft.
Craft Differentials
5 Peel Street, Granville
NSW, Australia
Phone 61 2 9637 1973


ADDING STRENGTH TO A 9BOLT REAR:
-Torco 85w140 RGO Mineral Based Gear Oil (2 required), 1 Bottle of Torco F Type Friction Modifier (Recommended for Cone Type LSD Units).
-Ratech Smart sleeve instead of traditional crush sleeve.
-Ratech Severe Duty Pinion Shims 1133. Adds reliability plus makes changing gears easier.
-Check posi and shim/tighten if necessary.
-TA Performance offers an Aluminum Girdle Cover and ARP Stud Kit for the carrier bearing caps. Highly recommended.
-Dry Film Lubricant on ring and pinion as well as internal carrier gears. I used Tech Line brand and applied it myself. Just check with your wife first before using the oven to cure it.....trust me! Seriously though, it's cheap insurance and you can get it from Jegs or Summit.
-Another option is Moser Axles. You'll probably break the gears first, but if you think it's necessary....they'll make you a set.
-Harrop offers a 28 spline Truetrac, and a modified 31 spline unit.


This is all the info I have to this point.
Good Luck! Dwain "Draino" Brammer

 

Thanks for making this a sticky!

 

Send a moderator of that forum a PM.

 

Lots of good info here! Though the rebuild info sounds like it came from the tech article. Thats okay, you provided lots of other info thats very usefull. My 9bolt is in desperate need of an overall. I wish they weren't so complicated.

 

What about the stock rear cover can you get that anywhere?

 

AFAIK it has been discontinued from GM, but I've heard that classic industries (nextgen performance) sells them. Or you may try a junkyard (sometimes they have a busted rear they'll part out.

 

Its hard to find anything in the junk yards around here i was so lucky to stuble across a b4c and get my 1LE parts.

 

Awesome info my friend, thanks a LOT!!!

BTW, Larry Burd sells shims for 9 bolts.

Ed

 

No problem Ed! I haven't forgot about the 1LE brackets we mentioned, or the swaybar....I've gone back to work and my boy is in the midst of baseball so I've been real busy.

If the street machine articles about the 9bolt ever arrive from australia, I'll post a copy of them or submit them to the webmasters....but it's been over 2 months and they still aren't here.

 

Would the cover possibly off some of the other cars with the 9bolt fit?? If they make it for any of them still.

 

Where's the best place to send a 9-bolt to be rebuilt and about how much would it cost?

 

Hmmm, no replies ... let me rephrase the question:

Are there any places that specialize in the rebuilding and repair of BW 9-Bolt rears? If so, what is the typical cost for an overhaul?

 

Yes, your local gm dealership should be competent enough to rebuild one (preferrably chevy or pontiac since they sold them and chances are they have seen a few 9bolt rears before).

As for a specific place that specializes in them, no...but I heard somebody say they got their 9bolt rear rebuilt by Jasper.

 

GM would likely not do a bench overhaul on a differentical, and instead insist on doing the removal and reinstallation. Since this would run-up the cost quite a bit, I'd rather do that myself.

Thanks for the lead on Jasper, I'll get an estimate.

-------------------------------------------------------------
JASPER remanufactures the complete line of
Dana, Chrysler, Spicer, Ford, and GM axles.

Jasper Engines & Transmissions
PO Box 650
Jasper, IN 47547-0650
Phone: 812-482-1041
Fax: 812-634-1820
sales@jasperengines.com
www.jasperengines.com
--------------------------------------------------------------

 

Any competent rearend shop can do it, it's just that you may have a bit of trouble finding the gears but once you do, you should be all set when you find a shop. A gear setup is a gear setup, no matter what the rearend.


Ed

 

I'll second that.

 

Thanks, all I'm interested in is rebuilding the rear with new bearings and replacing worn parts. The gears and posi unit are still good, but with 150K on the clock, it will need some attention. Fortunately, I have an exact 3.27 replacement differential from an F-body I can drop in if something breaks.

Any idea what a rebuild should cost? $300-400? $700-800? More?

 

Gear install and setup alone will be around $250-300. My suggestion is to find another rear, usually found for the same $250-300 complete.


Ed

 

Not interested in changing gears, I already have two BW 3.27 differentials, the one in the car has 150K on it and is getting pretty noisy, indicating it will need new bearings, etc. When it becomes undrivable I'll pop in the extra unit and have the other one rebuilt.

If anyone has experience in completely overhauling a BW 9-bolt, this is the price estimate I'm after, because if it will cost too much, then other alternatives need to be considered, such as a Moser or Strange replacement.

 

You've got all the part numbers and contacts for the parts you'll need. Total that up with what a shop will charge you for labor and....Viola!
Good Luck!

P.S. There's alot of guys who can competently set up a rear on the side w/o paying shop prices. AND there's alot of incompetent guys who couldn't even stick their thumb up their own *** who work in shops!
Ask around, talk to racers and hot rodders for a good rear man. Chances are you'll get one name more than others. That's your man!

 

I just rebuilt the 9-bolt I bought used, and it got very expensive. Randy's Ring & Pinion had a 3.73 gear set and a very complete rebuild kit (bearings, seals, crush sleeve, pinion nut, shims, etc.)for about $550.00, the cheapest I found and I'm in the parts business. My rear was from an F-body parts dealer and had been exposed to the weather for some time so a total brake rebuild added to my costs. With everything included (PB cables, brakelines & hoses, gear set-up, etc.) I spent about $1,400.00 on the swap from a 10-bolt drum rear. I'd reconsider a 9" if I were to do it again.

 

You were very close to a nice 12 bolt Moser or Currie for that amount of cash, but the 9 bolt will hold.


Ed

 

Hi All,

Thanks for all the great tech info on the 9 bolt.

Earlier today I contacted Borg Warner Australia to see what parts they still have for the 9 bolt rear. I spoke to a tech guy there for about 30 minutes about what can be done to these units. He was more open when I told him I used to work for Toyota Motor Corp Australia.

Nearly all parts are still available here in Australia.

He said that the 9 bolt is very similar to the independant rear on Commodores (4 door Lumina sized sedan or 2 door Monaro coupe aka current Pontiac GTO in the US). It originally was 7.6" ring gear for earlier Australian applications, 7.75" for US & UK export and some Commodore Turbo 6 & V8 models, and was also available in 8" and 8.5" ring gears. The 8" units were fitted to common later Commodores, while the 8.5" units are fitted to the current Falcon models.

I asked if the 8" and 8.5" units were a better option than the 7.75" - his response was that the 8" & 8.5" units are much lighter built, built to a cost, and as such are weaker than the old 7.75" setup.

GOOD NEWS - The LSD unit has recently been upgraded for these rear ends, and there is a retro fit kit available from them. It apparently solves a lot of LSD clutch wear problems. The only catch is that yo have to use their new LSD oil supplement, which consequntly isn't compatible with Viton seal materials. They can suply the additive to suit the new LSD units, and the new oil supplement compatible seals.

THe Hyratrack CANNOT be fitted to our 9 bolt rear ends. Apparently, the axles must have 2 more sets of splines on each axle for the Hydratrak unit to work at all. He said there is no retofit kit to do this for our rear ends.

Nearly all gear ratios are still availble. They definately had the 3.27 ratio I was after for my 1986 Trans Am. The 3.08 ratio is most common here, followed by the 3.45 ratio. They have most parts in stock here in Sydney.

MORE GOOD NEWS - If anyone else wants me to get any 9 bolt rear end parts for them, let me know and I will get back to you with prices.

Cheers,
ANDREW McKENZIE

 

Thanks Andrew,
Was the upgraded posi you were describing the HydraTrak?

 

Hi Dwain,

No, it is an upgraded version of our factory-style cone LSD unit.

According to Borg Warner, there is no Hydratrak retrofit kit for these 9 bolts.

Cheers,
ANDREW

 

I thought I read in another post that the new GTO is getting a 9 bolt. Anybody heard anything about that? If true, hopefully it will bring the cost of parts down.

 

Andrew,
What's it cost to get one of the upgraded retrofit carriers and any other required parts for the retrofit sent to Chesapeake OH, 45619?

 

One thing to note for all hopeful rebuilders....
When installing new axle seals (the ones under the caliper brackets) make SURE you remove the paint on the outside of the seal, if it has any... My rear-end rattled like crazy after the rebuild and I tore it apart 4 times trying to find the noise source. Finally, I noticed the P/S seal had paint scraped about half-way up the outside of it, then perfect paint the rest of the way. I broke out one of the wifes 4-way nail buffers (4 grits!) and took off all remaining paint, reinstalled the axle, drove the car, and smacked myself silly for not noticing the seal sooner!!

P.S. - Don't go nuts sanding, use the finest grit you can and leave a smooth surface for sealing

 

Im confused it Rattled cause of some paint on the seal? Didnt you put new seals on tho.

 

Yes, new seals. They rattled because the seal locates and seats the outer wheel bearings. With the seal only going half-way into the tube the bearing was moving all around and making a heck of a sound!

 

Ahh ok

 

I did a little burnout last night only to leave a one wheel peel =(. Looks like my posi is busted. I beleive it has the stock unit in it (auburn?) I'm wondering if eaton makes a 400# unit that will fit in a 9 bolt (maybe start a small dialogue about what posi upgrade options we have...) Thanks for all of the useful info BTW.

 

Just curious, but why exactly did some cars get BW 9-bolts and other get GM 10-bolts?

How much stronger is a 9-bolt over a 10-bolt?

Where can I find a Posi unit for my standard 9-bolt rear end?

 

No offense guys, but I took the time to research all there is to know in terms of what was offered and specs regarding these rears. All the answers to the basics (and more) is in the first few posts of this thread. IIRC I even categorized it so that people wouldn't be intimidated at the length of it, instead of reading through it to find an answer to their questions.

9 bolts were the hipo option from 85-90/91...at which time they were dropped supposedly due to higher cost (which makes sense due to them being imported)

Ebay or salvage yards that specialize in f-bodies are the best places to find 3 series posi's. BE CAREFUL WHEN BUYING ANY USED PART.

Again...not trying to be snippy, but I'm starting to see some questions here that are redundant to the info I first provided in the post. I'm trying to keep this post from going in circles for people who use search.

I wanted the mods to make this a sticky and lock it (so that the post could be strictly informational)...but that effort was futile.

Now I hope you guys see where I'm coming from and don't take offense.

 

I apologize, I should have read the post more thoroughly.

 

any one here open up the posi them selfs?

I just want to know what I should be looking for when I open mine up. (I guess pics are what I am looking for) also I did not catch if the carrier half bolts are rev. threads like the ring gear?

also why do I need to put the axle in the vise? won't a soft jaw vise with the bearing removed work better?

 

They're right hand threaded bolts.
That's the exploded view of your posi. No need to open it up unless you check it first and it's worn. Then you'll need to open it up to shim it.
most people have a regular vice, so if you got a soft-jaw one that'll work better...go for it.

 

I was wondering because the one under my car is a 1 tire about 75% time now. I picked up a used posi "low mile" any way I know that it will be worn no matter what the guy I bought it from said. that is why I want to open it up (then I will know for sure). I will be setting up this rear before I swap the axle and then fix the one in my car for a spare. I have setup lots of 7.5 10 bolts and a few ford 8.8 rears so the gear install is not the issue just the posi

 

Any thing on the ta 9 bolt cover?

I was woundering also i have a 3.45 9 bolt disc, and opened it up to change the fluid . I looked in it and saw something like a locker. Did this also come on this rear ends?

 

No lockers stock, sorry.

Ed

 

added link at next post

 

Hey Draino,

Unbelivable info, you've done a steller job and i i am thoruoughly impressed! You said that you had new moser axles custom made, i have a bent passenger side, and i dont have teh specs and haven't taken them out yet. Could you possibly give me all the specs i would need to get a new passenger side axle?

thanks,
Brett

 

No, I didn't have them made, I was stating that as an option.
Sorry.

 

draino, thanks a lot. I appreciate the quick response. If you know anyone who has had them made, please PM me their e-mail as I would love to talk to them about the specs. I have not actually pulled mine yet, so I was trying to get the specifications before I did it so I would have the rear end open as little as possible.

I have been reading about your 9 bolt covers. You have done an unbelieve job about the whole process, and I am thoroughly impressed with everything you have done. Keep up the great job! You are one of the people who keep Third Gen such a great place.

Brett

 

It was mentioned in the first post that the Dana 44 was the replacement rear for the 9 and 10 bolts as well as used in the firehawks. Does anyone know which part number or some way of finding this rear?

I might switch if it is cost efficient.

Thx

 

good luck, word of mouth is your best bet. very hard to find

 

Hey draino, quick question about the solid pinion spacer. I was looking to buy one and saw that the part number you listed corresponded to chyrslers 7.25 and 8.25 and ford 8 inch rears, nothing about a 9 bolt. Asked them about it and they said they dont carry 9 bolt solid spacers, could you clarrify? thanks.