terrcurr

Hey guys
Just bought an 88 IROC-Z, #'s matching 5.7 Litre, 700r4
I'm going to pull the factory 700r4 to keep it well, lol and put in a turbo 350, I can melt that one no problem at all...... hehe
I want this car bad a$$ from light to light in the city, and yes I'm a mustang hater..... I know theres many mods I need to do but lets start with what shift kit and rear gear you guys recommend to walk a stock mustang with an x-pipe and flowmasters... (theres a mustang guy at work who has a 5.0, x-pipe, flowmasters and a big mouth and fully intend on shutting him up..... soon)
Help me shut his face guys
Thanks

midias

This post is very confusing.

I would start by figuring out what you have already then make a list of mods you want and why.

terrcurr

Hey Midas.... let me explain....
Its a #'s matching car, tranny has only 60,000 miles on it... years ago I had an 83 trans am, put a shift kit in it and within a summer and a half that tranny was toast - dont want that to happen here and be forced into a costly rebuild to keep the car #'s matching, so Im going to install a turbo 350 and a good quality shift kit that I hope you can recommend and if that tranny breaks because of it, I dont care, Ill get another one.
And I would like to replace the rear gear so the car is stout in the city when a mustang wants to go.
The car is 100% stock except from the y-pipe back the exhaust is 3 1/2" to basic mufflers.

Future mods that will happen are... mild lift cam, headers (not sure if shorty or long tube, which is better?) complete exhaust from headers to an H pipe and back to ?? flowmasters?? not sure what mufflers to run either... :P
But right now, Need your thoughts on a good shift kit and gear to get started.
Thanks

Reid Fleming

iTrader: (2)

Going to a Turbo 350 is the wrong direction as far as I'm concerned. Why give up an overdrive? That makes highway driving annoying. Especially with a shorter axle ratio. On top of that, the TH350 has a 2.52 first gear ratio. The 700R4 is a 3.06

This means that a 700R4 with a 3.42 axle ratio in 1st gear would be the same as a TH350 with a 4.15 axle ratio....... But driving at 70 mph with a TH350 would result in driving down the highway at 3420 RPM (with the 3.42 ratio) or 4150 RPM with the 4.15 axle ratio.....Meanwhile a 700R4 would be cruising along at 2400 RPM in overdrive at 70 mph. Much more enjoyable.

Sounds like you need the same transmission shift kit that I have (and many others here have): A Pro Built Automatics "modified" TransGo unit. The Street/Strip version. I've had this on the car for 6 years now. A good transmission cooler (stacked plate design instead of tube & fin) is a good idea. And they're CHEAP! I did the cooler because I was moving to a hot climate (Houston, TX) that has lots of traffic.

Axle ratios: If your car has a 3.27 ratio, keep it. It's not worth going to the 3.42 ratio. And 3.73 is going to rev too high too fast. These cars are low to mid RPM power. Not no torque/high RPM turbo type engines that require a higher RPM.

If you have the 2.77 ratio, then I would recommend going to a 3.42 axle ratio.

Stick with short tube headers. Long tube are a nuisance in these cars. They're too low. They all scrape. And they don't make much more power if any than the short tubes. Muffler comes down to personal choice.

Want to blow away Mustangs? Put a torque converter in your car.
http://www.eecis.udel.edu/~davis/z28...age011026.html

Ron U.S.M.C.

terrcurr,
Stock meaning NO posi. is that correct ?According to tech data it looks like you may have one but I want to be sure that's the case.

Ron U.S.M.C.

If you do decide to upgrade I suggest something in a 28 spline.

Pro Built Automatics

If you are happy with the rear end gear ratio you have now, (good gas mileage, low rpms on the freeeway, etc.) leave it alone, except to make sure it is a posi (limited slip). A good Shift kit and a good torque converter will give you the most in terms of performance, (especially if you drive aggressive) and with out the loss of gas mileage on the freeway.

khulsebus

iTrader: (2)

The early 700R4's were fairly weak, but were redesigned in the mid-late 80's and made a little stronger. I've used both B&M and Trans Go in 700's when I rebuilt them back when I was working in a shop. The quicker shifts along with a trans cooler will help your trans live a little longer. I do agree with the keeping a 3.42:1 rear gear and adding a good limited slip. Before you start adding parts on the motor though, you should ditch your complete exhaust for headers, high-flow cat, and a good cat-back exhaust. Follow that by opening up the intake to let the engine breathe. Then go from there with your engine mods, and converter.

morgsie

iTrader: (1)

I've never seen any part of the car's VIN stamped on a 700R4. This isn't some rare 60's car...

midias

So you want to keep it matching but put a TH350 in it?

terrcurr

Yes ronusmc... the car has factory posi

Ron U.S.M.C.

I'm not real familiar with the stock posi. unit but I believe you can take a look at it to determine how much wear is on it and decide if you want to upgrade when you start to dig into the differential .Rebuilding a stock unit with new parts (posi./carrier,axles,ring and pinion,master bearing kit,axle seals and bearings ,support cover ,installation) is expensive but IMO worth it in my application. If you start to push higher HP/torque with sticky tires/slicks to hook hard its time for a 9" or 12 bolt.

khulsebus

iTrader: (2)

I rebuilt the stock one once when I was working in a shop, it was a lot of work just like anything else in the differential. It would be easier just to replace it, but I'm not sure which would cost more replacing or rebuilding it. If someone were capable of rebuilding a differential, it would be cheaper to rebuild the posi and replace ring and pinion gears that it would be to replace the posi with a new unit. Either way would have to replace seals, bearings and shims.

Ron U.S.M.C.

OK, I'm going to jump into"could be a dumb question"area and ask if its a Borg-Warner 9 bolt because Tech Data is listing 9 bolt ratios.
Open it up and see whats in there. If its a 3.27 9 bolt than you have a decent rear end (if the non-rebuildable as far as I know)posi. is in good shape than put it back together and simply install a Corvette servo.(you can do that your self for about $25.00 in a hour or so) in the 700r4 and race the guy. I don't know about yours but I bumped the timing on my little 5.0 and it definitely helped with throttle response off the line.The tires will make or break you off the line.

terrcurr

Yes, not dead set on that type of tranny, but theres plenty TH350's laying around in garages here for pretty cheap, if I break the tranny I'd rather break a throwaway and simply go get another one and keep the original safe, I dont understand why you dont get that dude??

Ron U.S.M.C.

OK, I got it, I am not trying to upset you because IMO working on modifications can be stressful but should be fun at the same time, especially on this site so if I keep bothering you in any way I will back out of this thread.



So as you know there are parts of the car that have to work together to get the end result you want.Posi., gear ratio, and tires are three of them. Sounds like you may have two of them .When you get your new trans.in launch it a couple times to see if you have the third.
With my posi. and the 3.42s I have to feather it off the line for a second then
WOT and they still spin a little with A rated street tires.
Back to my dumb question. What about the differential? 9 bolt or 10 bolt.

(88 IROC-Z A4 L98 V89.3:15.7 (350) 230@4400 330@3200 TPI--2.77*or 3.27* *Borg-Warner rear axle )( *RS available in California, Texas, and Florida only)

Pat Hall

iTrader: (31)

Whether it's a 9 bolt or a 10 bolt, the stock posi in either is really not rebuildable. You can get new cones for the 9 bolt posi, machine and shim them, and it'll fix the carrier somewhat, but it's a royal PITA to do, and usually doesn't last much longer anyways. Most of your 10 bolts got either the Auburn unit on the later rears, and the Eaton Gov-Loc on the earlier ones. The Auburn is not rebuildable in any way, shape, or form, and the Gov-Loc's are garbage from the get-go. So if you have a 10 bolt with the stock posi, do yourself a favor and get either a brand new Eaton, clutch-style posi, or a used Torsen posi from a 98-02 f-body rear. Your car being an 88, you'd have to get a set of 90-92, 28 spline axles for a Torsen carrier. Early '89 and older 3rd gen rears used 26 spline axles. So unless you can get a set of 28 spline axles cheap from a junkyard, it's probably better to just buy a brand new, 26 spline Eaton posi.