what is wrong with my drive train?

heres a video of what is happening. i may have mentioned before that there was a weird knocking sound when i would flirt with my gas pedal..

i replaced the front diff mount with a ply one and it seemed to get most of the bang out but heres what i found upon moving the drive shaft..

its a crappy vid but what you see is the drive shaft hooking onto the differential..
[ame=http://s96.photobucket.com/albums/l191/shirley1978/?action=view&current=Feb19_0001.flv][/ame]

it moves a few centimeters in each direction.. is there something wrong with my diff? i dont see the u joints moving.. any ideas? :clobbered:

Its difficult to tell from the video but that looks like maybe 1 or 2 mm at the sheild. My best guess is that's OK.

Paging Gary

Can't tell from the video but a little bit of play is normal, millimeters, not centimeters.....

If I remember correctly, your rear is sitting very high, the half shaft U-joints do not like that angle I assume.... look from behind/under the car when it's parked on level ground, the half shafts should be almost parallel to the ground, slight slope towards the wheels....

What you're describing sounds like U-joints.....the good news is: AutoZone has "BruteForce" solid U-joints for $15 or so and the install is not too difficult
:thumbs:

ok heres what happens..

im in second gear coasting. i floor it for a half second and let off and i hear a knock like someone is hammering the bottom of my car. i thought it was the front mount bushing on the diff but i changed that out and nothin.. i tried moving the half shafts and only one had VERY little play in it, the other was solid.

i doubt its the u joints on the drive shaft because the tko has only been there for 4 years max..

is this something to worry about or am i just being paranoid?

A long shot here but check your exhaust and see if its loose and banging around,if you have a broken hanger that would allow the exhaust to move around.

negative... solid

i think ill take a video when i have the chance to show you guys..

Shirley1978 said:

heres a video of what is happening. i may have mentioned before that there was a weird knocking sound when i would flirt with my gas pedal..

i replaced the front diff mount with a ply one and it seemed to get most of the bang out but heres what i found upon moving the drive shaft..

its a crappy vid but what you see is the drive shaft hooking onto the differential..

it moves a few centimeters in each direction.. is there something wrong with my diff? i dont see the u joints moving.. any ideas? :clobbered:

Click to expand...

Is this really moving a few centimeters? If it is that is a problem. Again, from your video it looks like 1 or 2 mm.

sorry .. i did mean cm.. :bounce:

that knock is just..... not conforting.. i need to change those u joints.. maybe that would do it..

i figured it was the diff mount b/c of the banging noise.. and my half shafts are pretty level with the ground. ill take a pic 2morro

I played that vid about a dozen times, I can't tell if it's the driveshaft input to the pinion or output to the 1/2 shaft, but either one can not have ANY later play in it, from the looks of it, I think it's diffy time.....input bearing on the pinion is my guess.....IF I"m right it's not that big a deal, it can be done failry easy, but that things weighs as much as you do....

:surrender:

Shirley1978 said:

ok heres what happens..

im in second gear coasting. i floor it for a half second and let off and i hear a knock like someone is hammering the bottom of my car. i thought it was the front mount bushing on the diff but i changed that out and nothin.. i tried moving the half shafts and only one had VERY little play in it, the other was solid.

i doubt its the u joints on the drive shaft because the tko has only been there for 4 years max..

is this something to worry about or am i just being paranoid?

Click to expand...

From this description I'd suspect the front differential mount - you already replaced that and you already ruled out the exhaust....
There are quiet a few things to check before you start dropping the differential, check the front trailing arm bushings and bolts. Maybe the bolts are loose and you lost a few shims - from what your describing it could be the trailing arm moving under load change.

Another question: you replaced the stock diffy mount with poly ?? The poly mount is taller than the rubber and this is changing your driveshaft angle quiet a bit. Did you ever check the angle of the transmission yoke and differential yoke ??? Did you ever have vibration problems after the TKO install ??

mrvette said:

I played that vid about a dozen times, I can't tell if it's the driveshaft input to the pinion or output to the 1/2 shaft, but either one can not have ANY later play in it, from the looks of it, I think it's diffy time.....input bearing on the pinion is my guess.....IF I"m right it's not that big a deal, it can be done failry easy, but that things weighs as much as you do....

:surrender:

Click to expand...

I'm with gene on this one...my diff flange has no lateral movement. If it's not the ujoint, maybe flange nut is loose or bad bearing?

I couldn't tell by the video. I don't like the poly mounts and would replace it with a quality rubber snubber. Not all places sell quality anymore but the one Bairs sells are what I use. There should be no inward movement in the pinion yoke, if you installed a Tremic check the DS angles as a lot of them are out of alignment from what I was told. I thought those were sold as "bolt in's"

There's no way you can sell a bolt in kit that doesn't require checking the driveline angle. If you want to install it yourself, invest in a cheap angle finder. It's just part of the process, just like dialing out the belhousing. If you can't measure and adjust the driveshaft angle you shouldn't be attempting to install one of those trannies in the first place. Still amazed at how many people report vibrations and then report never having checked/adjusted the angles.....come on now...what then hell!!!

the tranny was installed at my uncles shop (which is legit.) and i never had any kind of vibration in my drive train..

Gary, i bought 2 sets of front diff bushings, a poly kit and a rubber kit. right now i have the poly one on there, but it doesnt seem to be much bigger than the rubber one that came with it. acutually, the rubber bushing is bigger than the poly one. bought them from ecklers. can you elaborate why you dont like the poly bushings?

as for my trailing arms, ill have to check.

the driveshaft angle would be something i wouldnt know how to check.. :clobbered:

ive never really had issues with the drive train before untill it started making that noise. when my rear diff cover cracked my mechanic told me that there as some rubbing along the inside of the cover. he said he fixed it but the problem started after that cover was replaced.

also, the drive shaft u joint does not move at all, the movement is on the input shaft (or whatever its called) that goes into the differential.

ill take a vid to show you guys what it sounds like..

Some of the poly are not the same dimension as the rubber, guys that never had a problem got sucked in my the poly hype and had issues after using them. Same with poly trans mount. I tried ES trans mounts 3 times over 5 years, and every one was the wrong dimension throwing off the alignment. I finally had a ES tech tell me it was not correct for corvette, but the Summit or ES catalog never stated that. I still have a NIB poly sitting here on the shelf.
I'm concerned about what your mechanic found and did in the diff, there should not be anything rubbing inside- if so you have to fix it before it locks up the diff and breaks everything inside. If the pinion is moving into the diff you better stop and get it fixed, the preload on the bearings or the crush sleeve is screwed up- again a sign someone was in there. I fix these kind of things a lot and would love to talk to the mechanics that work and get paid for this work.

ill take the poly bushing back off, measure, take a pic of it. ill measure up the stock one and the rubber bushing that i bought for comparison.

gary you have pm