86.5 turbo swapped. no under cover no bottom rubber lip. when I get on it in a lower gear on the highway, the back end gets a little squirrley and it feels very unstable. is this a downforce issue or some type of suspension issue. or is the mk3 just a fat pig?
Downforce
- Thread starter madseacow
- Start date
If you don't have a lot of mods, I'd say there is a good chance you have some suspension or rear subframe issues. Early model MK3 supra's are known to have more brittle rear subframes. We really need more information though.
Brittle subframes indeed, mine just cracked, right below the pinion flange on the diff. 
I have the 89+ braces but they haven't been on the car for a while because I was trying to find a squeek back there so I was checking the half-shafts and just looking over things, then my subframe cracks, lol.
I think the 16 years without the bracing undid my 1 year with it, lol.
It's not like I had a rusty subframe either, it was 100% rust free (I sandblasted some surface rust off of it 2 years ago and coated it with POR-15 and topcoat, it looked better than new and should never rust.)
No big deal though, my brother is going to weld it, and reinforce it, he's had experience at his previous welding job doing reinforcements on similar cracks, etc.
I'd say you probably have some worn out shocks, probably some worn bushings, and possibly a bent arm or something. Check it out.
Included are some pics of my subframe after coating, as well as my diff, which was also sandblasted and coated. They were taken about 2 years ago.
I have the 89+ braces but they haven't been on the car for a while because I was trying to find a squeek back there so I was checking the half-shafts and just looking over things, then my subframe cracks, lol.
I think the 16 years without the bracing undid my 1 year with it, lol.
It's not like I had a rusty subframe either, it was 100% rust free (I sandblasted some surface rust off of it 2 years ago and coated it with POR-15 and topcoat, it looked better than new and should never rust.)
No big deal though, my brother is going to weld it, and reinforce it, he's had experience at his previous welding job doing reinforcements on similar cracks, etc.
I'd say you probably have some worn out shocks, probably some worn bushings, and possibly a bent arm or something. Check it out.
Included are some pics of my subframe after coating, as well as my diff, which was also sandblasted and coated. They were taken about 2 years ago.
Attachments
shocks are newish kyb gas. it's a swap so this is really the first time theres been power back there. rear subframe looks straight, bushings may be worn. I don't know how to explain the feeling. it's like I'm breaking loose in the rear but I don't see how that'd happen with only 3"dp back and k&n style. I have no spoiler and it only really seems to happen at high speeds. but how effective could a spoiler be?
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The spoilers that came on the mk3s don't do anything for downforce, they reduce areodynamic drag by like .01.
yes the supra is a pig,its heavy in all the wrong places. but i'd look into to which parts need to be replaced first like the shocks and springs. if they are are origional from 1986,they need to go. bushings might be ate up as well.
supraman7mgte said:
whoa now......thats totally wrong to say!
Its not that heavy...hell a first and 2nd gen Eclipse is 3300lbs!!!!!!
I havent really heard of our subframes cracking being a big issue....weird.
keep us updated
the supra is too heavy, it should be around 3200... If you've driven a mk3 which I assume you have siman, then you would know it feels pretty darn heavy. It might hide it cause its a nice ride. But saying the Supra is heavy is totally correct, no matter what an eclipse wieghs.
kwnate said:
I own one.....TEIN HA's, strut bars.....rebuilt motor....
yeah I know how they handle and I think they handle GREAT!
I came from a 2700lb civic Si......2 years ago...I know what heavy and light handle like. :icon_bigg
Don't get me wrong,this is my 2nd MKIII!!! I love my 1991 turbo targa,but seriously,this thing is HEAVY,but it's a sports car,not a 15 lb race car...
The sad part about all this is that my 70 chevelle when complete will probably wiegh less than my Supra... That thing looks like solid steel, and the little supra surprisingly is just as heavy... oh well, I'll love both the same, guess I have a thing for fat girls
Adjuster
Supramania Contributor
Check your lower trailing arms, and the bushings on the knuckles. I have one that is worn, and it allows the right knuckle to twist slightly under load, causing the rear to steer over to the right slightly. (I have to correct with right steer angle anyway.)
It is not breaking traction, it's just twisting up the suspension, and steering the car.
I've heard that upgraded bushings, and/or changing over to heim joints is the cure to this problem, but from the mods you listed, it really only becomes a problem over 400hp at the wheels.
Yours sounds like a worn out bushing to me.
It is not breaking traction, it's just twisting up the suspension, and steering the car.
I've heard that upgraded bushings, and/or changing over to heim joints is the cure to this problem, but from the mods you listed, it really only becomes a problem over 400hp at the wheels.
Yours sounds like a worn out bushing to me.