87IROC92RS

My 87 IROC has a rear pinion seal leak ( apparently did long before I bought the car ) changed the fluid, the U joints ( indexed the shaft ) the tires are balanced but even if I get going and put the car into neutral theres a deep low rumbling sound coming from the rear end, I also noticed doing brakestands, when the car shifts gears the car kinda lurches and I can feel a slight tremor ( it has a stage 1 700R4 ) I plan on swapping the seals soon but im fearing the lack of rear end maintenance and low fluid level when I changed it may have done something to the posi track. I also had to swap out the u bolts for the rear sway bar ( donor from my 92 RS as well as the diff cover ) due to the bolt snapping off from rust

gurkgurkgurk

u remember to add posi additive when u changed the fluid?

87IROC92RS

I added the 7 oz bottle of posi additive into a pyrex dish and measured out the correct amount of fluid ( 54 oz ) and the car doesnt drop fluid anymore and I check the diff daily to feel the level of fluid

87IROC92RS

Ok I just got back home from racing a Fox Body and I noticed the faster I went the worse the vibration got. I hit about 130 and I put my hand on the shifter and it was like a vibrator out of control... Thats telling me that either the driveshaft is indexed wrong ( marked it when I took it out ) or that its so out of balance. Im seriously at a loss on this one

Saber

iTrader: (2)

i know that when i had a loose tranny mount i could feel the vibration in my shifter. also your pinion angle could be off, causing vibrations.

87IROC92RS

due to the car having a trual dual ran UNDER the driveshaft I had to cut the pipes but I did try to remove the torque arm bolts in the rear, but never had the bolts completely out ( since you cant remove the back w/o lifting the body ) but I will check the tranny mount, it seems that it only does this vibration after 55 and the faster you go the worse it gets. could the pinion seal be bad enough to change the pinion angle w/o leaking fluid?

87IROC92RS

OK upon further analysis, the car seems to only vibrate at certain rpms and speeds. once it engages OD it kinda mellows out but when you get back in the throttle and increase the RPM's you can feel a low rumble /vibration through the entire car.

gunner53227

It could be a bad bearing.

Or what for me was the pinion gear. I must of abused my car too much one day, but after that day I had vibrations also. I was getting vibrations above 40mph, if I put it neutral it got better. I changed the u-joints in hope that was the problem, but still did the samething. I was on my way to the store; I stopped in a middle of a median after a car went by I gave it a little gas and my rear end blew up.

My pinion gear sheared from the shaft and blew the bottom of the housing. I didn't even step on the gas very much and it broke. I left a big oil stain in the middle of the road and it is still there 3 months later.

87IROC92RS

that could be a possibility, but when I changed my diff fluid I looked at the gears to make sure there wasnt any uneven wear or any chewing of the ring to the pinion. It prolly doesnt help either that the pinion seal is blowing/slinging oil out. Im hoping its just the driveshaft not indexed right ( even tho I marked it ) im gonna try in 90 degree intervals to see if it stops, if not im changing the pinion seal and checking the tranny mount. Just put the car up on stands so tomorrow I should get a better perspective ( tranny pan leaks slightly also so im gonna have to flush and replace that too ) ONly thing is they put a tranny cooler on it so im gonna have to play the measuring game since it usually adds about an extra quart.. not to mention its a stage 2 700R4

kit-ss

iTrader: (1)

I've been working on a vibration for two months now and I'm running out of money. Finally got all the parts for a rear rebuild. Thank goodness it didn't blow yet. Anyone know how to identify the housing. Mine has 1987 stamped on the bottom and it's in a 91 TA.

87IROC92RS

I found out 1 part of my problem.. when I had the rednack a$$hole at the local muffler shop re-weld my exhaust the tailpipes were hitting the diff yoke, so I made a reliefe cut in the bracing they used to space the pipes, sectioned it out, and welded it back up. It doesnt rumble as bad now but im thinking that Sears inflated the tires way too much so im gonna de-air the fronts to 30psi and the rears to 28psi

87IROC92RS

Solved part two of the vibe problem.... Sears had one of my rear tires at 36.5psi one at 34psi one at 33.5psi and one at 32psi, so I aired the fronts down to 30 and the rears to 28.5 so that elimenated the high end speed vibe but it still has its pulsing vibration at that magical speed/rpm range between 45-60

gunner53227

It could be a tire out of balance or bent slightly. My dad had about the same problem, when he got on the free way and right when he reached 55 it started to vibrate also.

Or a weight fell off, maybe sears didn't put one on all the way and it flew off.

87IROC92RS

I've isolated it to the right rear tire as the source of the vibration, checked then dbl checked the wheel weights and they are on so its either a bent rim or I have issues with the axle shaftor a worn out wheel bearing allowing the wheel to rock back n forth

87IROC92RS

bump

Saber

iTrader: (2)

IS there any noise associated with the wobble? My rear tire had a slight vibration and i have a bent axle, but i also have a squeak like you wouldnt believe? How much play is in your axle?

87IROC92RS

I can pull on the tires to see the in/out play in the axle and its minimal at best I yank on the tire the car moves with it, no noise at all.