What all will i need to do this swap? i plan on taking the original powerglide out of a '68 chevelle and sticking it in my 87 IROC. And then put my 700r4 back in the chevelle. Just wondering if any of you have done this before and what parts i will need, thank you.

 

not sure what you need, i just would like to know why you wanna do it
if you're trying to make the iroc faster, i think it'll slow it down unless you do some gear work because even though it's a 2 speed, i think it came with some economy gears (not geared for fast acceleration)

 

there isnt a torque arm mount on the powerglide. im sure u know that...but u gotta figure out what ur gonna do about it.

good luck

 

The powerglide swap is almost identical to a TH350 swap. Dimensions are the same. A powerglide has a coarse spline input shaft so it uses it's own torque converter. A turbo spline input shaft can be installed to use TH350/TH400 torque converters. I use ladder bars so I don't have to worry about the torque arm mount.

There are a few different powerglide trannys. Early models have a secondary rear pump so that the car can be push started. These are not very popular since it requires extra parts when the rear pump is removed for a transbrake installation. They also come with 2 different first gear ratios. 1.82 and 1.76. The 1.76 gear set is the stronger set. If the tranny was originally behind a V8, it probably has the 1.76 set.

Your "14 second" 87 would do much better with a 3 speed like a TH350.

 

Well the way i look at it, faster isnt always better. Im trying to build a cheap high 12 to low 13 second bracket car to race in the modified class at NRP. Ive got 4.10 gears and an eaton posi, so that should help it as far as acceleration goes. I also have a vortec 4-bolt 350 that im dropping in. Its got 2.02/1.60 valves and a Comp Cams XE cam with like .530 lift or somethin like that. Im hoping to get close to 350rwhp out of it. Im also using a TCI trans brake, LOOKING for a 3000 stall converter, and using a 2 step. I might install an electric shifter to. Ive got an 89 RS that im going all out on so im not worried to much about making this car fast aslong as its safely in the time limit for the MOD class, which i believe is a 13.99

 

I dont think that it will do any better than it would with a powerglide, It may go faster, but like i said before im going for consistency, not fastest E.T. 1 shift is alot more consistent than 2, atleast from what ive seen.

Do you think that i will need a longer driveshaft then? maybe one out of and earlier model 3rd gen will work since they came with TH350's (i believe) I think i will use ladder bars aswell.. if that will solve the mount problem. Thanks for the help so far, i appreciate it!!

 

The reason I don't suggest the PG is that you're not producing a lot of torque or have the gearing to multiply available torque.

I switched from a TH400 to a powerglide mainly for a weight saving and a reduced HP loss through the tranny. My engine produced about 560 pounds of torque which can easily compensate through the 1.76 first gear to get the heavy (over 3000 pound) car moving. Last year I was using 4.56 gears with 29" tall tires. This year I'm dropping back to 4.30 to bring my shift point down a couple of hundred rpm. I also use a 5700 stall converter. My 60' times should slow down but my ET will improve since I'll be able to pull through the gears better without having to shift over the HP curve.

A heavy, low torque car can better use a 3 speed tranny to help get it off the line.

Engine torque X first gear ratio X diff ratio will give you the final torque to the wheels.

Lets say your engine makes around 400 pounds to torque. Through a 1.76 first gear PG to your 4.10 gears. That's 2886 pounds feet to the wheels. Using a TH350's 2.52 first gear it comes to 4132 pound feet. An extra 1000+ pounds of torque to the wheels will get you off the line much quicker and it's only a few hundred lower than what I produce to the wheels. Even switching to 4.56 gears with the PG won't produce the same amount of torque as the TH350 with 4.10's

On the other hand using a 700R4 with it's very low 3.06 gear will produce over 5000 pounds feet and can easily spin the tires without some good slicks. The bad side is that the gear spread to too far apart between first and second to make it a good racing tranny.

Also if the car is street driven you won't like the PG at all.

A PG is almost the same length as a long tailshaft TH350 which is almost the same length as a 700R4. The same driveshaft can be used on all of them.

 

I know i can get more torque at the wheels with a TH350 but im not really worried about how hard it leaves, i actually want it to "crawl" off the line. A t-brake and two step with the rev limit set at 2200-2800 should help me do that since my cam is alittle on the big side. The only time i plan on drivig the car on the street is when i take it to the track so im not really worried about streetability either. I just want it to run the same time, every time, and hopefully make me some money!

Where did you get your latter bars? how much did you pay for them?

 

i see where you're going with it now
good luck man, and let us know how you do

 

Private sale, used, $20. I had to buy the mounting brackets to put it onto the diff and some front mounting brackets plus all the mounting bolts. I also needed to buy and weld on the safety loop around the front rod ends. I fabricated a crossmember to attach to the front and welded all the brackets to the diff with reinforcing plates across the brackets.

There's pics on my web pages.