I've had a thump on acceleration from a dead stop in the rear of my 96 ever since I bought my truck a year ago. Every brake part on the rear of my 96 is new inlcuding the flex hose, cables, tried 2 sets of shoes, drums, hardware, cylinders, and steel lines yet I still had that annoying thump under acceleration from a dead stop Today I replaced the rear flex line - it was still there....I decided to pull my rear axles again and compare them to those in my old 88 parts rig....

The 88 was definitely in better shape concerning the spiders, side gears and the axle splines....The 96's were worn pretty good. So I swapped everything between the 2 trucks....Sounds much quieter and the thump is less noticiable but still there. The U-bolts are tight (new rear springs 1.5 years ago), the u-joints were new a year ago (spicers), all that's left that I can think of is to replace the lower rear sway bar bushings...they are getting bad....Frustrating as hell this is. I've been chasing this thump for a year now...Any other idea's???

 

Try greasing the splines on the slip yoke next time you have it apart. Mine has been doing this for a while. The grease fix lasts a couple months on mine. I believe Ford has an upgraded part to fix this.
I hope that I could help.

 

I agree with greasing the slip yoke. The difference is instantaneous and amazing. I've been thinking about drill and tap the yoke for a grease zert, so it can be easily greased when oil is changed. Has anyone done this?
Frank

 

I have asked this before with no responses.
Which slip yoke are you greasing, the one at the transmission or the one at center carrier? If just at the transmission is this on a one or two piece driveshaft?

 

I have heard many people talk about the faulty slip yoke causing problems when not properly lubricated. Are talking about the mid shaft slip yoke on a 2 piece driveshaft of the yoke coming off of the t-case/transmission?

-Chris

 

My 90 F150 4x4 with E4od, has a slip joint on the forward end of the driveshaft. The U-Joint is attached to the forward end of the slip joint. Hope I explained this well.
After chasing a thump for many months, finally took the rear U-Joint off and dropped the shaft. Pulled the rubber boot loose and stuck a finger full of grease in the female section of the slip joint. Problem solved.
Been about 3 months and it is coming back.
Looked to me like there is enough room past the splined section of the female part, to drill and tap for a zert. Not sure if this would get the grease down in to splined section where it is needed, or if it would fill the cavity, and not allow the male section to slide in when it needs to. Hoping to find someone that has already done this modification.
Sure be a lot easier to pump a grease gun, than drop the shaft.

The guy that runs the local driveline shop is a former GM transmission specialist. He warned me about his experience. Said GM refused warranty repairs on automatic trannys when they found grease inside them. Seems that if grease is applied to the output shaft, heat and the slip joint moving in and out, can force the grease past the rear seal, and into the tranny.

There is no possibility of that happening on my truck, but thought I should metion it as a potential problem.
Good luck Frank

 

I read on another forum that there is a special GE grease and if you use it, it will not have to be re-greased for a long time. But I also heard it was very pricey.

EDIT:
Here is the quote I talked about.
Pics of Grease I used for Slip-Yoke
A few months ago, a thread about slip-yoke grease came up an I had mentioned what I had used. Long Story Short: GE Silicones does not make it anymore and for a long time it was not avaliable. Well NOVAGARD makes it now and this is what the tube looks like
It should be about 20$ to 25$ US
Never had even a hint of a Bump/clunk/thunk or what ever other sound you want to call it since using this stuff.

 

I'll try it tonight, The thump is much less noticiable and the rearend is much quieter now that I swapped out the axles and spiders/side gears....I think I did this once already with no change but I'll try it again....I have a good connection at a driveline shop, I might go see him about having an output shaft for my t-case coated like those on a big rig. Does anyone know if the output spline on the t-case (BW1356/4R70W) is the same as the output spline of a C6 or AOD???...I have 2 extra F150 driveshafts here.

 

I greased the splines last night, problem solved....I guess I'll have to do this every so often to keep my sanity...LOL....It only took 5 minutes so it's no big deal...Thanks guys.

 

Glad it worked for you.

Does anyone know where I can order the NovaGuard Versilube?
Thanks Frank

 

I'm trying to find out if replacing the slip yoke may be the way to go. The next time I need to replace my u-joints, I think I'm going to get a new slip yoke, $40 is worth not having to remove the driveshaft every couple months. Now if I only had a reason to replace the u-joint, until then I'll keep greasing.

 

I'll see how it works out and for how long, if it's short lived I'll follow your lead.