RocketyMan

So my '84 z28 has an open dif with 3.73s and I feel this is way too low since it runs out of breath very quickly in 1st gear and in 5th gear I'm already at 2000 rpms going 50 mph.


So I'm wanting 3.23s with a limited slip to bring down the rpms and upgrade the diff.

The budget I'm planning is around $100-$150. The pick-n-pull around my place sells rearends for around $100. I need to know what donor cars would be a good choice for a GU5 and either series III or II. I'm not sure exactly what type of posi I would get.

So far good donor cars with chevy 10 bolts would be:
Camaro/Firebird (duh)
Blazer 4wd
S-10
Chevy Astro
Monte Carlo
El Camino
????


So anyone please chime in for donor cars that would work and thoughts about series III or II for axle spline count. I don't really expect to find something with a disc brake rearend.

jmd

iTrader: (4)

I like the idea of a Torsen (Eaton sells the Truetrac which is similar) so to get your budget...

See if you can get 28 spline axles from a 90-92 third gen and a 3.23 from an automatic G92 99-02 F-body or a 3.42 from a 6-speed car.

RocketyMan

So a 28 spline would be series III, right?

And yeah... 3.23s seem like they'd be a performance automatic gear, right?

I don't know how many f-bodies I'm gonna see at this junk yard. Mostly sedans, suvs, and trucks. So I'm not sure what to look for that would have Eaton posis specifically...

jmd

iTrader: (4)

No. The II / III break is still 3.08-down = II and 3.23-up = III. Axle spline count has no bearing on this.

2.73 was the base gear on all auto LS1 F-bodies and most(?) LT1 F-bodies and the non-G92 6 speed 1993 models.

3.23 was the optional gear on all auto LS1 F-bodies and most(?) LT1 F-bodies plus the G92 6 speed 1993s.

3.42 was in all 6 speed F-bodies 94-02.


I've no idea on when Auburn cone style and Eaton clutch pack type posi's were used.

BTW across the 8.5/8.6 and 7.5/7.625 10 bolts,
30 spline axles are thicker than 28 which are thicker than 26.
Just another reason to go w/ the later 28 spline axles (instead of finding a 26 spline carrier and keeping your axles.)

RocketyMan

Oh ok..I see. So basically 7.625" ring gears use the 28 spline and 7.5" use the 26 spline.

Anyway, what are the pros and cons with Auburn and Eaton? Any preference? I'm not sure what I would most likely find in the junk yard and if it's year dependent.

But both carriers should be interchangeable with the gm 10 bolt, right?



Oh I found so good pitting in Timken race. Probably from previous owner not changing the lube as often??

jmd

iTrader: (4)

No. The 7.625 gears were a rolling mid 1980s change that did not coincide with axle spline changes. Is that '84 gearset 7.625 or 7.5? For some reason I thought they started on the 3.73 gearsets in '85; other ratios later years.

28 spline axles were maybe in third gen F-bodies in '89 but not 100% until sometime later in '91 or '92. S-10 also had 26 splines in some until at least '91.

When pinion gear bearings loosen up over time (usually before the carrier bearings) and the gearset starts putting powdered metal into the gear oil, it wears through the hardened surface of the bearing race and the result is seeing inner metal like what you're holding.

The 7.625 gearsets fit the 7.5 carriers and vice versa.

An Eaton clutch type is theoretically more rebuildable than an Auburn cone type. While Auburn parts appear to be available from Jegs, the wear surface against the outer face of the cones is the carrier. So if that is allowed to wear to the point of scarring that surface, the carrier is junk.

RocketyMan

I didn't measure the ring gear at all, but I counted the splines on the driven axles, and they're 26 spline. The 3.73s are stock from the RPO codes and I believe are original to the car. I'm guessing the ring is probably 7.5"

Is there an easy way to tell if the spline count is 28 or 26 without pulling the driven axles out? I'm guessing now I'm just going to have to pull a rear end from something at least '90 and later.

I thought GM usually stamped something on the side of the axles to help identify what was in them.

DJP87Z28

More reseach before asking about a gear change. Your replies show your lack of knowledge on the subject and you have not reached the question about installation.

jmd

iTrader: (4)

The spline o.d. is larger by 40 or 100 thousandths IIRC. Externally, I know of no way to tell.

The Torsen 7.5 10-bolt carrier only came in 28 spline.
If it's a G-body rear, it's 26 spline.
New body S-10 should all be 28.

Other than that, start pulling covers.

RocketyMan

djp

That's why I'm asking questions--because I don't know or unclear and not sure.

I know about installation with shims and setting a good wear pattern and ultimately getting it back on the car. BAM, done!

I just need to know about finding a good donor rear end and what's inside.

RocketyMan

Ok...so I scrubbed off some rust on the axle tubes.

I think it says "6KM 6527 1" I'm almost certain its "6527" or maybe "6327"


So this is for curiosity. In the Haynes book, "6KM" is SUPPOSE to be posi! But I ended up with an open and the console RPO codes say nothing about G92 or G80.

Maybe the book is wrong. "6PM" should denote posi and not "6KM."

This is what the book says about the other 5 digits.

"6527 1"
6=manufacturer -where?
527=5 month, 27th day?
1=day shift?

jmd

iTrader: (4)

Perhaps the 527 is 327 = Julian date.

Any possibility the 6 is a G = Detroit? That's what it was for 2nd gens anyway.

https://www.thirdgen.org/forums/tran...ifing-4th.html

RocketyMan

Well the car was made in Van Nuys from the vin#. I don't think they'd ship rear ends from MI to CA. But I guess they could.

But yeah..the picture is very misleading. The 5 is suppose to be a 3.

Rancid87

I dont know if youve found what you need yet but I have an Eaton Gov-Loc G80 posi diff with a set of 3.08 gears from an 84 that would bolt right in. They were pulled at about 45000 miles. Email me at jvmesquire@gmail.com if you are interested.

RocketyMan

Yeah..with the weather still being very wet and cold over here, I still have yet to make it to the yard. I'm looking for 3.23s because I don't want to change out the spedo drive gear.

3.23s posi with the 28 spline axles is the sweet spot.

But speaking of which..I should call the yard today anyway.

RocketyMan

Alright...so pick n pull is having their thanksgiving sale this weekend where everything is 50% off.

So anyways, I was looking for cars in the GM section, RPO coded GU5 and G80 (hopefully). I found a bunch of blazers and a few Astro vans and actually two third gens!

Anyways, ALL the 4x4 blazers or astro vans were coded GU6 or GT4 with the G80, which was NOT what I was looking for. And they also were 60" rear end not 62."

The only vehicle to have the 3.23s or GU5 was one of the thirdgen v-6 (vsux) camaro. Only it was open of course... :/ This camaro btw is a '92

So my question is this '92 camaro SHOULD be the 28 spline count axle regardless it's a v-6 right?

And for the G80 or locker diffy, what are your guy's thoughts. I heard stories of lockers handling poorly and maybe even exploding potentially.

JamesC

iTrader: (5)

If you haven't, may I suggest that you peruse the following 10-Bolt FAQ, which should answer many of your questions:

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

RocketyMan

I already read that...and it doesn't specify if it matters if a v6 will have different spline count. It just says 90 on up have 28 spline counts. So then can I ASSUME the rearend has a 28 spline count because its a '92 regardless its a v6??

JamesC

iTrader: (5)

Whether the car is a V6 or V8 doesn't matter.

JamesC

RocketyMan

Yes! Ok good! So I know the driven axles will be the same length and 28 spline because they're off a '92 rearend.

I think I'll pick up an additional G80 off a series III carrier and it should work with my 3.23s, right? The G80 is going to be off a like '98 blazer.

RocketyMan

Ok...so I went to the yard earlier today and I already knew what vehicles I wanted to pick from. The '92 camaro's entire rearend and a G80 diffy from a '98 blazer. Since most blazers came with 3.73s so ohwell.

One thing that really pissed me off was someone took locking lug nuts and stripped them on the hub! Look at the picture. Of course I'm not going to have the key-chuck to unbolt the lug nuts..but not only that, whatever a$$ did this to both sides and put two on each side!!! Seriously!?!

RocketyMan

Here's a closer picture of the locking lug nuts...I tried vice grips and just can't get enough leverage without ruining my vices or hurting my hands.

Does anyone have any ideas??
I don't want to break off the lug nuts or anything.

You can see my other rearend matches completely with the original one.
Also that's the G80 gov lock diffy I picked up as well.

JamesC

iTrader: (5)

The Gov-Loc has a very poor reputation on TGO, so you might consider a search before you install.

JamesC

9340Ruby

iTrader: (7)

I had the same issue one time. I just took an old socket and hammered it on. I then took an impact wrench to break it free. Hope that helps.

RocketyMan

Well this is going in a low HP car...and the carrier was in an LTE Bravada; Luxury Trim Edition that is..and from judging from the looks of the governor, it didn't look like it hit the locking mechanism all that much. So I doubt it got any severe use out of it. Also, the magnet only had the normal itty bitty small wear particles.

Now that I look and think about it, I think that's what someone ended up doing is jamming a socket on the lug nut and blasting it on there as tight as they could. I don't understand why!

I'm just going to find a junk socket and try it.

RocketyMan

Screw it...i'm just gonna have to get a hack saw and chop off the four total lug nuts. I spent 2 hrs trying to grind the nut down so that the vise grips can get something good to bite on. But whatever...broke the vise grips.

I'll just punch out the studs and put new ones in anyway. I noticed looking at the stud post, they looked bent really bad too. Whichever...it can be fixed.

RocketyMan

**UPDATE**

So I got the lug nuts off with a pipe wrench, and rather effortlessly too! My dad and a friend actually recommended it.

Anyways, I got the spedo gear needed to compensate for the 3.23s going in. This project is moving rather slow due to a really cold garage thanks to the weather.

I was surprised I actually found one at one of my auto parts store using the p/n 3987918 for the 18 tooth driven gear. Got it for $6.48 after tax. The lowest on ebay was a lil over $10. So I'm happy I found one and have it in hand same day for under $10.

RocketyMan

***UPDATE*** 12/27/11 - Almost ready to put her back on!

Ok...so I put a new pinion seal on the front and used some loctite on the pinion nut and tried setting the preload on the timkens. I'm not sure what 12-15 inch lbs feels like, but nobody had the beam style torque wrench in inch lbs. I basically guessed and snugged the nut down using the same crush sleeve. I didn't change any of the shims or anything on the pinion bearings.

Now I'm ready to set up the ring gear.

This is where I'm having problems. I used some grease to see what the wear pattern is like on the right gear. Here's two pictures of the drive side and coast side.

RocketyMan

I'm trying to look at these two patterns of drive and coast, and am having a hard time deciding if this is "ideal" or not.

I need some experienced opinions. I only changed carriers in this project. The carrier bearing spacers are all very similar with the ones I got.

Two of the spacers are .235"
One is .234"
Last one is .245"

I'm not sure how much this will change the wear pattern on the ring ring gear granted with what I see in these two pictures of drive and coast.

Please tell me what you guys think.