driveshaft vibration

[shocker998md]

so two days ago i changed the rear pinion seal and changed the gear oil in the rear end. while i had the drive shaft out i replaced the u-joints and put everything back together. I went out and took it for a spin and once i got to 40 mph i had i pretty nasty vibration. So i was looking at my driveshaft and noticed i had a weight on the drive shaft. So i figured that i must have put the drive shaft in reversed and that i need to flip it around so that the drive shaft is balanced. So yesterday i switched it around and now i dont have the vibration untill 50 mph. I checked the gear oil level, because that is the only other thing that i tinkered with and it was good, so im guessing somehow my drive shaft is out of balance . Does anybody have any ideas.

 

[Alky V6]

Something was upset when you had the u-joints changed. Re-check the u-joint installation, have the driveshaft checked for straightness, and have it rebalanced.

Also, check the rear bushing in the transmission for a good fit. An excessively worn extension housing bushing will cause vibration, and if bad enough, a leak too.

 

[shocker998md]

another thing i thought of is maybe the coupling that holds the u joint that is bolted to the pinion isnt tight enough....im not sure of the actuall term for it. could anybody give me a torque on that nut besides stupid retart tight, because that what it was to get it off.

 

[Alky V6]

another thing i thought of is maybe the coupling that holds the u joint that is bolted to the pinion isnt tight enough....im not sure of the actuall term for it. could anybody give me a torque on that nut besides stupid retart tight, because that what it was to get it off.

I check the play of the pinion by yanking it around by hand. It should have no play.

The pinion nut should be tight enough to prevent it from backing off on its own, but not so tight that it affects the pinion bearing preload. Use red loctite. Get it too tight and you could burn up a pinion bearing.

 

[shocker998md]

do you know the torque on that nut, ill be dropping the drive shaft tomorrow. ill back the nut off, wire brush the threads and then put some red locktight on and torque it. i checked auto zone and they cannot bring that torque up.

 

[Alky V6]

It's a little tricky on a pinion with the crush sleeve already set. Before you remove the nut, and assuming that the pinion bearings have the proper preload at this point, measure the turning torque of the pinion using an inch/pound wrench. Remove the nut, do your prep and loctite and replace the nut tightening it until the turning torque just starts to increase from the value you originally recorded. The important thing here is not the torque value on the nut itself, it is the preload that is put on the pinion bearings by the tightened nut. It is the turning torque in inch/pounds needed to turn the pinion shaft. A turning torque value other than specified by the manual can result in premature failure of the pinion bearings.
I would recommend that if there is no end play of the pinion shaft, leave it alone. If there is endplay, you should disassemble the rearend to see if there is a worn bearing that is causing the excessive play.

 

[driveshaft man]

Trans slip yoke was part of balanced assembly.If you did not mark it prior to disassembly,you might have flipped it 180* when reassembling.Hopefully you didn't swap ends with the slip yoke. Another possibility is failure to install the snap rings on the cups that fit into the rear pinion yoke.That is what centers the u-joint in the yoke.If the trial and error doesn't solve it ,a balance job is less than $100 (starts at $40 here)
Torque is 100-125# .Not too critical as long as you don't overtighten and crush the sleeve . Just clean the nut and threads very well and use red Loctite.As stated before ,there should not be ANY side to side of pinion yoke.Its hard to use the preload method without removing axles and installing all new bearings unless you measured it before you disassembled it.

 

[asloan5]

If you dont fix the vibration eventually it will ruin the transmission case because the bushing will not stay in because the case will have wallowed out .... ask me how I know

 

[shocker998md]

well i fixed it, or atleast i think i did. theres no viberation all the way up to 90, and then let out of the gas and coasted to 40 and is was smooth as glass. i just kept on messing with it and eventually it all lined up right. thanks guys