I have a bone stock 1988 gta, with the TPI 350. It has an automatic transmission. It also has a limited slip rear-end, and 4 wheel disk brakes. The car drives wonderful, and only has 45,000 miles it was my dads.. and after years of maintaining it for him he gave it to me. I know you all prefer the t5, but i want to keep it automatic. My question is I am planning on starting a major buildup on the motor, and want to know what transmission i have and what it will horsepower take. Also what the rear-end will take.

Also what can I do to help strengthen then the transmission and rear end, and help them perform better.

 

The real questions are: How much power will the motor produce? How will the car be driven?

A 700R4 can easily be upgrade to 550-575 HP with a Pro-Built rebuild kit.

The 10-bolt rear will break before the trans. Your problem there is going to be torque. Especially if you want the car to hook up at the track. It can be beefed up, but again, how much power? Slicks? Drag raidals? Street tires?

 

the car is not going to be a drag car.. i just want to build a really fun toy. will only drive after work, and on the weekend.. have 4 cars so this one is for fun. I am planning on doing a top end buildup: heads, manifold, cam, exhaust, msd and then a 9psi supercharger, with intercooler.. from what i have read i will be looking at 450 -470hp at the crank... just wanted to make sure the tyranny would hold it... i am expecting to need to replace the rear-end. and no slicks... just the best z rated street tires i can find... just tryiong to figer out what i can do before i need to replace everything

 

If you already plan to replace the rear just replace it from the get go. I'd do that first. Get a 9" or 12-bolt with the gear ratio and differential you want and bolt it in. The 10-bolt will definately go before the trans, so why waste money trying to beef it up if you will just inevitably replace it?

Then I'd look at doing the trans. A TransGo shift reprogramming kit will wake up the shifts without being overly harsh like a B&M kit. A Vette servo will get you more holding power, and make it live longer. Both items come in the Pro-Built kit, which I recommend to anyone building a 700R4. The kit is $475 and includes everything (clutches, steels, 10-vane pump guts, Vette servos, TransGo kit, etc). It's the most complete kit around, and the best. It is good to 550-575 HP, so I'd say you're good to go with it. Get a good converter too. Probably a 2,800 stall or so. I like Continental converters for non-lockup applications, which if the car's just a toy I would recommend going non-lockup.

For the engine a good top end is a good course of attack. I would change the bottom end prior to installign the blower though. A blower application really should have forged pistons, and these motor's don't stock. Also at those power levels you are past the strength limit for stock rods. A set of Eagle 4340 H-beams can be had for about the cost of reconditioning the stock rods, so they are cheap insurance. A stronger crank isn't a bad idea either. Studs in the mains and heads are a must as well.

For heads use AFRs if you want aluminum. If you want to stick with iron Vortecs are a great head, just keep in mind you'll have to run a different intake manifold.

Just some thoughts...

 

thanks... that is some great info... I was aware of having to beef up the bottom end.. but not planning on doing that for bout 2 years when I do the supercharger.. but the general consensus is that if I don’t it will last for a little while, but, it will eventually destroy itself... so thanks for the confirmation... any idea how much the transmission kit would cost to have installed... I am still learning about cars... and transmissions scare me.. I know plenty of ppl to help with the motor... but no help with the trans.. a simple shift kit I have done... but what you are talking about seems a lot more involved...

 

I typically charge about $700 to install the kit. It is involved, and time consuming to do the job properly. Various clearnaces get blueprinted, which requires repeated assembly and dissasembly, just like blueprinting and engine. The pump halves have to be sent out and machined. There's a lot to it. The transmission is completely rebuilt, and upgraded to handle 550-575 HP.

Where are you located? I'm on the East Coast. Pro-Built is on the West Coast. If you're closer to the west I'd say send it to him. If you're closer to the east I'd be happy to take on the project when you're ready.

 

It seems like it would be cheap insurance to have someone that knows what they are doing to do the rebuild... i live in california, sacramento... so it is a little far... but thanks for the referal i will definetley look them up, any idea what a rear end with posi would colst me that could handle that power?

 

Yeah, if you're in California definately check out Pro-Built at www.700r4l60e.com Everything I know about these transmissions I learned from Dana. He's the best around. I started doing 700R4s when I needed to do one for my truck. No one aroudn here knew squat about them. Everyone said they weren't strong enough, swap to a TH350, etc. I found Pro-Built through TGO and the rest is history. From the first time I spoke with Dana I had an instant confidence level with him. He clearly knew what he was talking about, and obviously had success with 700R4s using his parts and methods. I called him about five times during that build up and he spent about two hours total time with me on the phone making sure that I got everything right. When the trans was finally done and installed I tested it out and was amazed. It was smoother than it had been stock, and much more than it had been with the previous B&M shift kit. Once it was warmed up and I'd gone through the gears manually I cracked the throttle for the first time. I nearly got whiplash when it shifted, and the tires actually spun on the 1-2 shift! Needless to say that sold me on Pro-Built.

It's been a while since I priced out bolt in rears, but I think you're looking at about $2,500-$3000 wheel to wheel. A 12-bolt will be a little cheaper than a 9" typically. A lot of things influence the cost like what differential you decide to use (range from $350 for an Eaton posi to $500 for a Detroit Locker), if you decide to get new rear brakes (several options like Ford Explorer discs (a very nice system BTW) or LS1 rear brakes, etc), what kind of axels you use, etc.

I'd get a rear that is just a bit of overkill for your needs. That way you'll never have to worry about it. I'd say a good 12-bolt with 33 spline axels, an Eaton posi, 3.73-4.10 gears, and a girdle cover would do very nicely with your plans. Stepping up to a 1330 or 1350 yoke and accompanying driveshaft is also good insurance, especially with all the instant torque of a blower.

 

I would check on the rear, if it's a GTA, count the bolts on the cover and make sure you don't have a 9-bolt, which is stronger than the 10 bolt rear, it has a 7.75 ring gear vs the 7.5 in the 10 bolt rears, and I'm beliving that all GTA's had the 9-bolt until GM quit using them.

 

I just crawled under my car it has the 9 bolt rear. does this mean the rear end it worth building up rather than swapping? it hooks up really well, and it has the factory posi, and it will roast the tires all the way through first. and chirp them in 2nd.. and remember it only has 40,000 miles on it so it should still be in good shape.

I really don’t want to cut corners, I want the car to be reliable, but I don’t mind saving a couple grand either.

 

The 9-bolt is a bit stronger than the 7.5 10 bolt but if you are going to put anything over say 400hp to the wheels, you would be better off getting either a 9" or a 12 bolt to put under it that can handle the power. The car has a 3.27 rear in it according to the gtasource page which was the only ratio available in '88. The 9 bolts are hard to get gears for, only ones I've found are 3.70 and 3.73's which are considered to be "noisy" on accelleration and decelleration. I'm about to find out, I found a factory 3.70 9-bolt rear in a junkyard and it's going under my GTA to hook up to the LT1 and 6-speed I'm putting in the car.

 

With a 7.75" ring gears vs a 7.5" ring gear the 9-bolt is only marginally stonger than a 7.5" 10-bolt based on rign gear size alone. A 9" has a 9" ring gear, and a 12-bolt uses a 8.875" ring gear. These are a lot stronger.

However, the 9-bolt uses a better factory posi and better axels, without c-clips. It is a better rear all around than the 10-bolt. Lots of guys have had good luck running some serious power through these rears.

But, like Klortho said if you are going to get serious you'd be better off swapping to a 12-bolt or 9". Parts are easier to get, and cheaper, you get a wider gear ratio selection, a differential selection other than just a stock limited slip, and stronger axels. Any good aftermarket 12-bolt uses 9" style bolt-in axel retention without c-clips, and all 9"s use this system.

 

well it seems like i will need to save up for the new rear-end then, thanks for the info. It seems like I will need to stick to the original plan and swap out the rear... mabie i can wait till i get the top end done then do the rear-end. it should do till then.. thanks agian for all of the help...