quick info needed?

[Texasmustang]

ok this is the first time ever installing upper lower control arms on any car i have owned. my question is i put bbk on my 86 and was wondering can they throw off the pitch of the rear end? i have tried everything and still get a slight vibration around 70 mph. i have changed the tranny mount to a shorter one, new u joints and balanced drive shaft, re clocked the shaft and no matter i put the shaft it same speed and vib. i was wondering could it just be low on gear oil maybe i didnt put enough in it? next it seems like the motor and tranny sit a inch forward could that have caused my drive line to be that far off to cause this? thank in advance

[shumpertdavid]

have you had the tires balanced?

[Texasmustang]

Yes they are new and fresh balanced. If I put the rear end and go through all the gears it's fine til 4th gear at 70 and 5th gear at 70. Not really sure how to describe the vibration. Or it might be low on fluids in the rear. Cause I took that rear end out put my 7.5 back in that I knew was pretty low on fluid cause it was leaking it. And got the sane noise or vibration at same speed. I might try tomm and just add a Lil more fluid and see. But I know I am stumped and if I can't figure it out I will just drive it till it breaks. I guess lol

[Texasmustang]

could it be the isolator caps for the springs? i noticed they seem to look pretty bad and might be rubbing metal to metal on the control arms.

[Texasmustang]

also the car was original a automatic. should i buy a 5/8 drive shaft spacer too? the tanny mount is all the way forward on the crossmember just wondering if thats cause car was built for a auto. and i measured the 4cyl donor k member motor mount holes vs. this cars 6 cyl holes and both are 16 inches from the firewall forward. but ui noticed when i installed the 5 speed i had to cut the floorboard forward for the shifter to clear. isnt the 5 speed tranny shorter than a auto tranny? cause i am thinki about doing the drive shaft spacer to see what happens

[turbos66coupe]

If it only happens at 70mph it sounds like a tire issue. Does it go away after 70mph. Even though they are new doesn't mean anything. Did it start after the tires where put on.

[Texasmustang]

It does it weather the tires are on or off. So cant be tires.

[holeshot]

Possible bent axle.

[71chevellejohn]

Have you had the driveshaft balanced?