FRporscheman

I just converted my '84 with the rear suspension assembly out of an '86 NA. I used the '86 entire assembly including torsion bar carriers, end mounts, trailing arms, everything. The mileage on the donor car was somewhere between 100k and 150k (it's been over a year, I forget the exact number), and I got it from a junkyard, so I have only visual inspections to go by. But it looked good.

I just finished the swap today and took it for a test drive, and it feels really weird. The best way I can describe it is it feels like you're driving on ice. The front steering if fine, but the rear feels like it wanders, almost like the rear end is steering a little. I double checked everything, torqued every bolt to spec, it all went together ok. This is my second rear suspension swap - the first one went without a problem. No strange noises.

I'm about to get under there and look for something I might have missed or messed up, but honestly I think I won't see anything (because my untrained eyes won't notice the problem). Can anyone offer any advice?

UPDATE
see page 3 for the pics...

87 944 C

did you get it aligned?

MAGK944

+1 rear height, camber and toe alignment needed. You were probably just lucky with your first swap.

Thats assuming the rear offset, sway bar and wheels tires are as before you converted.

FRporscheman

I just got under the car and was poking around when it dawned on me: The first swap was actually just a remove/reinstall of the car's own suspension, and this one is a whole new assembly, so like you guys said, it needs to be aligned. DUH

I used '86 parts to keep the same offset as before, and I'm using the same wheels (Fuchs). The torsion bars and sway bar are new, but from my research, they are the same size and stiffness as before.

Thanks guys! Now I need to find an alignment shop very close by...

odurandina

you been hanging with JPM's pit crew ?

DER951

I'm also going to be doing this swap, taking out a conventional '86 951 rear suspension and replacing it with one from an '86 with t-bar delete and leda coilovers. I've driven the lead car on the track with no issues. Will an alignment be needed after the swap? Also replacing the front struts with ledas from the same donor car.

MAGK944

You will definitely need and good alignment and a corner balance will also help in a track car.

I dont know how others do this but I disconnect the f&r sway bar drop links and arrive at the shop with 1/2 tank of gas and they corner balance with me seated in the car. Then they align f&r and reconnect my drop links. I fitted adjustable drop links last time which allows me to set the sways without any preload after the alignment.

btw you need a special tool for the rear camber/toe adjustment. It's cheap at all the usual vendors here.

Legoland951

I replaced my old 1984 car with a 85.5 whole rear suspension complete with the torsion bar housing, sway bars, trailing arms, brakes in one piece and tracked as straight as an arrow. No irregular tire wear and no alignment needed unless the donor car was misaligned or had a bent frame.

I also bolted a 86 turbo brake setup directly on that 85.5 n/a suspension.

FRporscheman

Frank, do you consider yourself lucky that the 85.5 rear suspension didn't need alignment, or are you saying that's the way it should be?

MAGK944

It is feasible that if no dismantling of the complete assembly happened or bushing and height changes were made, it would track fine. Thing is you have a tracking issue so that is not the case. If you get the alignment checked the figures will tell you were the problem lies.

Funn944

I'd get a good 4 wheel alignment done. I had one done to mine by The Winning Formula in Louisville, KY and it made a huge difference.

Legoland951

If the rear alignment is straight on the donor car and you remove the entire assembly in one piece, no alignment is needed unless the mounting points on the frame is not in the right place (bent frame/chassis). If you remove the trailing arms from the torsion bar housing and took it out in multiple pieces instead of one assembly, you will need a complete alignment.

Yes assuming both alignments were good and frames are straight, you need no alignment.

MAGK944

Not entirely true. How do you know either/both cars were not lowered either on the eccentric or tb reindex. If you fit it to the new car and the height on the new car is the same as before, then yes I agree. If it isn't you need to set height and alight. Setting height alone doesn't work because as you lower or raise you change the camber.

The op has a problem and the only way to resolve it is to find out what is wrong by having it aligned.

mytrplseven

I replaced the tie rod ends and sway bar bushings while having the front end dropped to do the oil pan gasket. I counted the threads on the tie rod and was close but the steering wheel was just a hair off. With new tires/wheels and all the other work, it only seemed prudent to get an alignment done (4 wheel) and It was definitely off, not much but enough to get right.

jharding

FR,

Did you replace the stub axles too? They are different from 84 to 86, and will change the rear offset.