M1028 shudder when deceleratong at hwy speed

[shotty]

Leaving dallas headed east with a fully loaded m1028 pulling a loaded m101a2. Truck makes sounds like when you drive over the rumble strips whenever I let off the throttle at highway speeds. Otherwise only does it down to about 45 mph then other stops. Going to continue east,don't have time to sit around. Let me know what you guys think.

 

[cucvrus]

Sounds like motor mounts or a loose accelerator bracket under the dash. Is it just a sound or is it a vibration you feel in the chassis?

 

[shotty]

I can feel it in the truck

 

[shotty]

Let's talk ujoints and such, since this seems related. Output shaft of xfer case has a bit of verticle play in the bearing. The ujoint on the output shaft is screaming hot. Not the whole thing, just the two bits on the output shaft. The other two are cool. Same with the rearmost ujoint. On the rear I did feel a bit of play though. Going to look in to replacing them before I leave town. Anything else you think I should look at? How concerning is the bit of output shaft play? It's still running cool.

 

[cucvrus]

Look for dented rear drive shaft. But bad U joints are a definite issue. that will do it hands down. That was a trick question. You knew the answer. i was guessing from afar. Have a Great Day. Good Luck.

 

[shotty]

Pulled the drive shaft, it's got a small dent in it. Not new, but yeah. Fighting the ujoints now

 

[cucvrus]

Fighting U joints? Dented shaft will make a vibration for sure.

 

[shotty]

Yeah they didn't want to come out, and I'm working with limited tools. I have my shop press j. The truck, but it's literally buried under everything else I own.

Got them out, and new one in but it was way too tight no mater what I did. I think the inside face of the driveshaft had some burrs and made the bearing cup too small. Cleaning them up and trying again.

 

[steelsoldiers]

Back in about 1996, my 1009 CUCV would eat a rear u-joint about 5-6k miles. No matter what I did during the replacement process or what type of u-joint I used, the result was always the same. We checked the runout on it and it was just slightly out of true. I ended up calling Six States and ordering a new heavy duty driveshaft. Problem solved. Hopefully, just changing the joint will fix your issue. If it eats another one, then I would pull it and take it to your local driveline shop to have it checked out.

 

[shotty]

Ujoints fixed the issue. there is still a small dent in the driveshaft but it's been there along with those u joints for the last 30000 miles that I put on this truck. I'm sure it will be fine for a while but I will order a new drive shaft eventually. thank you for all your help and ideas I'm glad it was something simple and I'm back on the road headed east now.