mine started doing this randomly about 2 months ago. it's in the shop right now, we believe the axle bearing's need replaced. (fingers crossed)

 

Good choice.

 

I am waiting for my new driveshaft to come in from Driveshaft Specialists in Texas. My truck has always had the random "slow down, hit the gas, random clunk." I kind of ignored that until it also developed the "slip, slip, bump" on take off from a stop. I greased the slip yoke to some relief, but it returned within a few weeks. When I called to ask questions about their driveshafts, he started asking questions. He seemed really knowledgable about the F-150s driveline issues. Two questions he asked me were really interesting:
1. When you slow down, do you ever get a "thump", like the transmission bumps into gear?
2. Sometimes when you slow down do you ever get a "shudder" around 35 and slower MPH?

Number 1 I can get used to, but number 2 has gotten on my nerves since I bought the truck (until the recent "slip, slip, bump"). It feels like the transmission shutters when shifting from 3rd to 2nd sometimes. He told me it was caused by "spline-binding" between the factory slip-yoke and the transmission output shaft. That he said, is caused by the weak factory u-joints and the angle of the drivshaft on the 4x4 models which also puts more wear on the slip yoke. When I ordered my replacement unit I upgraded to the 1-ton u-joints. It should be in any day now.... Fingers crossed! I will definatly keep this thread updated. I love my truck and this has been my main complain with it.......

 

fixing the slip yoke of the driveshaft is fine, but the addition of a tuner will program the shift points and will stop the problem permanently. I have experienced this on both of my f 150's and this definately cures it. Replacing or greasing of the yoke is only temporary and only masks the issue. Give it a few miles and replacement will happen again. Mine was so bad, that I had to replace the pinion bearing in the rear end on my 2005. It had slammed the rear end so much that it cracked the bearing race. Ford knows that the issue exists,,,,that's why they offer torque adjustments. Save your money and install a quality tuner.

 

2010 F150 4.6 6sp. auto 4X4. Man this blows!!!! My truck slams so hard from 2nd to 1st it scares me (and my passenger when I have one). I tried to utilize the lemon law on one of my ford trucks a few years ago but it was futile. What a p.o.s.. Last Ford for me, my other ones have been crap too excepting my 96' F250. I should have my head examined for giving them another chance. So-long Ford you can be assured I'm spreading the word.

 

Mine was a simple fix. It always seemed to happen on mine when I was rolling and stepped on the throttle slightly and it down shifted form 3 to 2.

Disconnect the battery.

The computer has adaptive learning that includes shift points. When I disconnected my battery it reset the ECU. Driving it from that point I never had a problem with the clunk. That why some people report fixes with a tuner.

 

well at least we narrowed it down to 500 possible reasons.

 

mine does it and I have a tuner....

 

I bought my 08 used last summer with 20k on it. I had the exact same 3-2 clunk and also a 3-4 flare all while driving slow on tip in. There is a TSB for the 3-4 flare to reprogram the PCM. I had it done still under warranty and it actually fixed the 3-4 flare and the 3-2 clunk does it about 1/2 as much as it used to and it is way less severe now. There is a TSB for this 3-2 clunk on earlier 04-06 I think that says it is a normal characteristic of the transmission. Not sure why it is still "normal" on my 2008?

 

+2..well said.... lunge on me trying to catch up.... . i feel this in my 05, even with a programmer

 

hi i have a 1998 jimmy but its a little different. if i drive normal not trying to get up fast it shifts perfect but if i try to get up a fast (shifting between 1800-3000 rpms) it slams into gear (this is only 1st to 2nd-2nd to 3rd gear). it doesnt make a noise i can just feel it instead of shifting smooth it jerks. is this something i should fix??? thx for replys

 

Uhhh - why are you posting that here? Go post on a GM forum!

 

I have also had this problem since new in 04 2wd supercab with the 2 pc driveshaft. I would get a hard shift up or down 1-2 or 3 to 2. I lived with it for 7 yrs and it seems to be getting progressively worse. So I had the shaft pulled for inspection and they greased the yolks. I was expecting to hear the coating had warn off etc but the report came back that the yolks had grease and looked great. I'm leaning now to what some of you above have mentioned...perhaps the torque converter locking or unlocking in an un-smooth manner. But now at 120+K maybe I should just let it go.....

 

I'd never let a paid off truck go. If the transmission fails I'll get it rebuilt. Engine fails I'll get it rebuilt. Cheaper in the long run than new truck payments.

 

Excellent point...By let it go I meant quit letting the problem bug me...I'll keep the truck