Transmission Vibration
 

Today I had my car up on blocks with the wheels off. I let it run for a long time until it warmed up 170F. To my surprise when I had it running at 60 MPH and going nowhere, there was a rather strong vibration when it shifted into 4th. So I guess that is the front planetary bearings on the way out. Prior to this I thought it was my wheels being out round but now I am not sure. I think it is the tranny. This could be a way to check on Tranny health.

Not necessarily....if you had the car supported by the body and not near the outer ends of the control arms the cv joints could be at such an odd angle that they caused the vibration. Most manufacturers recommend never operating drive axles in the air for that reason and because the joints could possibly be damaged by doing so.

I suppose a way to double check would be to run it up to the same speed in third and check for the same vibration.

It's been a while since I've worked on an SVX (I bought a new one in '92, sold it in '96 and now I'm thinking of buying another - I loved that car) - are the rotors held down by screws? If not, at speed they too could cause vibration without the wheels holding them in place. This is an obvious situation, but sometimes we overlook some things...

Good Luck,
Beav

I believe that it is "verboten" to run the SVX drive axels with all fours in the air. As a matter of fact, I don't even believe you're supposed to run on a two wheel dyno. Be careful.

I suppose another simple but not so obvious situation would arise when the ABS sensors began detecting differences in wheel speed and started staggering power output....

Hi Beav,

Welcome to the club. Thank you for the input. The wheels were off and the blocks were under the suspension. The front blocks were under the bolts for the ball joint and the rear was under the lower control arm knuckle. The CV's were at the proper angle. The car weight was on the suspension.

Yes the ABS lights come on but the system does not try to brake the wheels. The light comes on when just one of the front wheels is spinning. This happens until the differential warms up and then both the wheels spin. The ABS light goes out after the car is run on pavement and stopped and started.

The disks are held on with the lug nuts or yes the disk will wobble around.

Randy,

Thanks for the advise on not doing this. One has to be real gentle with the brake pedal because the drive train will stop real fast without the momentum of the car.

The service manual actually says to do this, run the car on a lift after it is warmed up, to check out the proper voltage for the lock-up solenoid. So maybe it isn't a good idea and the service manual is wrong? Check out section 3-2 page 181 of 1992 SSM

Out of sheer fustration for a lack of SVX RWD I have done this on my other two Subaru's and the rear wheels spin on those cars.

A two wheel dyno used for emissions testing in the lovely state of Ohio is what destroyed one of the transmissions in my car. The highly unskilled operator noticed that the car was attempting to crawl off the rollers when the rear wheels engaged. Being the ever resourceful type he found chocks and straps to lock the car to the ground, destroying the transmission. Both the operator and the station supervisor VIGOROUSLY denied any wrong doing and until the dealership (Bishop Buick/Subaru in Akron) convinced them they were wrong. When all was said and done, their negligence cost them almost $6000 (tow bill, transmission, labor and rental car) and cost the station supervisor his job for being such an xxxhole to my wife.

I certainly won't argue with the service manual. Have at it. :D

Thanx for the welcome.

I didn't mean that the ABS would be shuttling, but rather the effect it could have on the transfer clutch (I assume that's how it decides to apply power from one end to the other.) If it operated quickly it might give a the vibration sensation. But I agree, no reason to question the manual. *S*

Beav

That is quite a story. Maybe I could use that approach to get a new tranny! We have the dyno test in NJ.