m3srt

iTrader: (2)

well guys I just got my built 80e and yank 3600 installed again ... I let it break in for over 1000 miles before. Start getting on it .. Well over 100 mph I get a really really bad vibration I let off the gas and it slowly stops as my speed decreases .. Well I took the driveshaft off and had it balanced .. He said it wasn't that far out of balance .. I put it back on .. I still have a pretty good vibration but not as severe ... And also it kind of hums and also the noise quiets down ss the speed decreases to less than 80 ... I don't understand what else it could be ... Maybe the tires are out of balance ? The weird part is that before i broke the 80e I had no problems with vibration at all at 130plus ...

iamkeniff

iTrader: (16)

Did you shorten the driveshaft? The 80e is a tad longer than the 60e which will cause that, plus it'll start to eat u-joints left an right

Camaro Zach

iTrader: (7)

One of the problems is whoever replaced your driveshaft put the wrong u joint on the rear. It is about 3/32" too narrow to seat in the rear yoke properly.

TXsilverado

iTrader: (19)

also check the operating angles of your CV joints. the rear of the trans may need to be shimmed, or the rear end may need some adjustment.

iamkeniff

iTrader: (16)

Damn how do you install a u-joint that isnt 1350 when the truck and driveshaft came factory with a 1350 u-joint


If he cut the trans crossmember like everyone else then there is no guess work if it was welded back flush. A buddy of mine had to have his dshaft shortened bc of his 80e swap and it ate ujoints like crazy

m3srt

iTrader: (2)

No I didn't shorten it I had 2inches of room from the driveshaft

Camaro Zach

iTrader: (7)

These 1/2ton trucks do not have 1350 u joints.....

His driveshaft was replaced a few years ago by the dealer and on the rearend side it has slack side to side. Meaning you can bolt down the straps with the driveshaft 3/32" off center..

The transmission crossmember is to the factory dimensions. I made it over a year ago.

On the driveshaft length if anything it is too short and would need to be re-tubed because it has ~2 of forward slip.

iamkeniff

iTrader: (16)

2007+ is 1350

Daryn's 2007 gmt900 was 1350, my truck is 1350, skipperdaddys is 1350, carbongmc is 1350, skoalbandit is 1350.

So i guess just our trucks are the oddballs driveshafts with 1350s from the factory as for the gmt800 platform that is a 3R u-joint

1K.260

I had a similiar issue when I changed my u-joints and I didn't use the C-clips on the inside of the rear yoke. The factory joints were epoxied in and the new ones needed the clips.

If the shaft has any movement in the yoke it will vibrate for sure. As soon as I drove it I know something was amiss so after the clips went in the vibration was gone.

Edited to add that yours may not need the clips and have a positive stop in the yoke, my donor 14-bolt has the 1350 yoke and has the stops in the yoke.