Getting a new driveshaft- thump on stop/pull away and vibes at 0-15mph.

[Stevedbvik1]

so i have owned my 2021 fx4 since new. i noticed right away a thump when coming to a stop and also when pulling away from a stop. I also noticed a vibration when accelerating from a stop till about 15mph. I took it in to my selling dealer who applied a tsb where they added shims to the rear.

here is a more recent one but it's basically the same as the one from 2021.
https://static.nhtsa.gov/odi/tsbs/2023/MC-10233590-0001.pdf

it moved the vibes around a bit but didn't do away with them. The thump, well they weren't too excited to address but i had found threads on this being due to lack of lube and presented my case to them about ordering a clamp and lube kit so that they could lube the spline. It was on backorder and they basically jsut dropped the ball, and i said eff it, and I've jsut driven that way since then. Hasn't gotten worse in 20k miles but i have moved to a new area and decided to take it in for the above issues as well as the trans shifting wonkiness.

They came back saying trans is fine and that i need a new driveshaft- which they have ordered and they said, "driving with it like this, may cause more damage".

I did some searching and found a tsb:

Technical Service Information 23-2251

So they are replacing the driveshaft and i am hoping that fixes the shudder AND the thumping coming to a stop.

With that said, as I have the shim kit already installed, how will that interaxt with the new driveshaft? Will they need to remove that?

Being that I am up on doing my own maintenance myself (rear diff done etc), what will they touch that i will need to check behind? Will they have to drain the rear diff? Will they have to remove the rear wheels?

thanks!

They replace the driveshaft with the one that the Tremor uses. Thats why they have to change the pinion drive flange. The driveshaft on the Tremor has a Rezeppa cv joint instead of a normal ujoint. That would explain why the the seal replacement and gear lube being required as part of the procedure. So yes they will have to drain the fluid and possibly remove the wheels if the axle shafts need to be removed to facilitate pinion flange replacement

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[silverflash]

They replace the driveshaft with the one that the Tremor uses. Thats why they have to change the pinion drive flange. The driveshaft on the Tremor has a Rezeppa cv joint instead of a normal ujoint. That would explain why the the seal replacement and gear lube being required as part of the procedure. So yes they will have to drain the fluid and possibly remove the wheels if the axle shafts need to be removed to facilitate pinion flange replacement

ahhhh, didn't know that. hopefully they get the part soon. I know my lemon letter still hasn't been delivered after 8 days. There is a mixup in the warranty manual for my 2021 that has 2 different zipcodes for the same exact po box and city. One ends in 121, which is in beginning of the book, and one ends in 126 which is where it says to send the letter. The postal worker said that was wrong and used 121 instead...... I don't know who is right....

 

[silverflash]

update: wasn't supposed to get a new shaft till end of july but one showed up friday and was installed monday. vibe is 90% gone but i still feel a very slight vibe which seems to come from the front- which is weird. Maybe that is something else. It's almost unnoticeable. The other issue, thump when coming to a stop and then again moving from a stop is mostly gone too. it did it once or twice but it wasn't nearly as bad. If it stays this way, i am good.

the shaft looks different to me, as i recall, where it mounts to the rear diff. I think i had u joints back there but now there is a drumlike thing. Also and exposed part of the shaft. See pic.

 

[Stevedbvik1]

update: wasn't supposed to get a new shaft till end of july but one showed up friday and was installed monday. vibe is 90% gone but i still feel a very slight vibe which seems to come from the front- which is weird. Maybe that is something else. It's almost unnoticeable. The other issue, thump when coming to a stop and then again moving from a stop is mostly gone too. it did it once or twice but it wasn't nearly as bad. If it stays this way, i am good.

the shaft looks different to me, as i recall, where it mounts to the rear diff. I think i had u joints back there but now there is a drumlike thing. Also and exposed part of the shaft. See pic.

That’s the driveshaft thats in the Tremors. That joint is called a Rzeppa joint ( like a cv joint).

 

[silverflash]

That’s the driveshaft thats in the Tremors. That joint is called a Rzeppa joint ( like a cv joint).

ahhhhh, gotcha. thank you!

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