Well here is the story....
This past weekend I went on a houseboating trip and obviously did my best to break some traffic laws. The car was loaded up pretty good and I spent most of my driving in 6th gear...even the hills.
Anywho, the car started to get a bad vibration on the decel. So bad that if would vibrate the change in my console

I start driving to work today and I get BRUTAL vibrations in 6th gear @ part throttle, 1800-2000, 100km. The night before I didn't get anything really.

I made some calls and the guess was that it was the DS yoke because the way it was shaking the shifter (side to side). I changed it and the old one was dry but not ceased. There was also alot of oil under the car

As the story goes, the guy at the driveline place said that if that didn't fix it, it is probably the tranny.

A couple small things that I would think might effect it was that I got new tires last week. Maybe REALLY out of balance and wheel nuts loose? Probably would cause ythis much vibration

Any Ideas?

Andy

 

Ok, a couple of things.
1) do you mean that you changed the u-joint rather than the yoke?
2) did you check/change the u-joint at each end of the drive shaft?
3) did you check the oil level in the tranny? If you have an oil leak, that would be my first priority, next would be to fix the oil leak.
4) if a piece of the clutch disk let go, this too could cause a vibration, however it should be noticable even in neutral at 2000 rpm. (maybe not)
5) if the tranny was shot, then I would think that some vibration should happen in any gear at that certain speed at which you are travelling in sixth when this happens.
6) I believe that Dextron III ATF is the recommended fluid for that tranny, start with that.

 

You have a custom DS or stock?

 

well i got a t56 for sale if you need one.

 

1)do you mean that you changed the u-joint rather than the yoke?
-We changed the joint in the back. We inspected the front joint and it was fine. There also was also a typical amount of play from the drive shaft where it enters the tranny
2) did you check/change the u-joint at each end of the drive shaft?
-no, the place I went to (GREAT PEOPLE btw!) where closing in 15 min, so all we had time for was the joint because that seemed like the logical place to start since it seemed pretty stiff
3) did you check the oil level in the tranny? If you have an oil leak, that would be my first priority, next would be to fix the oil leak.
-no, there was just red tranny fluid leaking out when we pulled the DS and spread around underneith the car. It looked red which is encouraging...rather than silver.
4) if a piece of the clutch disk let go, this too could cause a vibration, however it should be noticable even in neutral at 2000 rpm. (maybe not)
-This would suck because I bought a Street Twin (used but very little KM) for big $$$:S The vibration is there at most rpms, but only really bad in 6th
5) if the tranny was shot, then I would think that some vibration should happen in any gear at that certain speed at which you are travelling in sixth when this happens.
6) I believe that Dextron III ATF is the recommended fluid for that tranny, start with that.

-it is the stock DS with a 1350 joint. Apparently guys with 9-inches can get away with that...unlike with the 12-bolt.

-thanks Roy

 

my car just recently started doing the same thing. vibrating on the decel. started right after a hard 1st-2nd shift but its only done it on 2 occasions. i had my 6th gear replaced along with all my synchros about 2 years ago. but that was because it got stuck in gear and wouldnt come out.

if your tranny was gone i dont think it would do it in just one gear and just on the decel. if it is on the decel id guess drivshaft u joints/yokes. or your 9 inch you raved so much about

 

Put the car up on stands (under the axle tubes) and idle it in gear.
Take a good look at the driveshaft to see if it runs true.
Could the driveshaft have hit something?
Just a thought.
Gerry

 

did you check the tranny mount as well??

 

i was thinking the same thing lol

 

some guys with aftermarket rears (cough MOSER cough) run into problems when their driveshaft is too long and the front yoke bottoms out in the tranny... hopefully you have some play there for it slide back and forth like a **** in a ****.

Also, you beat on your car VERY hard when the geometry was bad - I hope this didnt upset the tranny. Now that I think about it, maybe the clunking was your driveshaft yoke bottoming out in the tranny when you were flooring it and getting wheelhop

 

Ok, I had no idea he was running a 9 inch and that there was a possible problem with driveshaft lengths. Definitely, if the shaft was to long, even if he got away with it for a short period of time, as time goes on and mounts begin to fatigue, at some point the driveshaft could easily bottom-out and cause ghosts to be heard.

Check it out with the jack stands under the rear diff housing in order to simulate road and load situations. Have someone add their own weight to the rear bumper and check to see if the shaft is coming into contact with the tail housing of the tranny. If so , well, you know what to do. Good luck, man!

 

I had a DS problem although I think I got lucky and did not damage the tranny.

I took the stock DS to a shop and send, "Make me one the exact same length with 1350 yokes both ends."

They made the DS the same length, but the 1350 yoke is obviously bigger and longer thus the overall length ended up about 3/4 longer then the original.

I did not notice this when it was installed but it tore up the dust boot on the end of the tranny and pushed the tailshaft forward and destroyed the pilot bearing in the block.

It looks like I got lucky as that appears to have been the only damage. However, I did not notice any tranny problems at the time.

so you might want to check the DS length and make sure there is some play.

 

I'm not sure if the length is the problem. The 12-bolt is the on you need to have a shorter length for as far as I know. I'm going to check the torque arm bolt to see if they are all there and tight.

 

the TA bolts are known to come loose or break off on these aftermarket rears. that would deffinatley cause some vibration.

 

BTW I know how to make a LS1 DS fit our cars with a 12 bolt or 9 in. Mail me if you want the info