Jay T

My differential is probably the culprit with my 03 150 4x4 V6. It has new ujoints and after you start moving it clunks and you can feel it sort of push the truck like your being kicked in the back. (not that extreme tho) It doesn't do it when you let off the gas though, I would expect it to clunk.

I know diffs are not cheap to repair, I'm wondering if it would be cheaper to pull one from a salvage yard.

Maybe its something cheap like the side gears or something....oh I hope so....

torkum

Could be carrier bearings are bad.
A used unit might be cheap to buy but what would you be getting. I think a good repair will be worth more in the long run.

cole_ford

well that depends. I have had this problem before. For about a year and a half, I tried two different forums trying to get some advice on what I should do(this one, and one other ford forum). I wasnt sure what I should do, pull from a salvage yard, buy a reman. buy brand new, have a shop rebuild it, or rebuild it myself. Alls came to an end, when I was changing axle bearings one day, and my dad was there with me. He was looking over my gears, and found that the side bearings were shot. Lucky for me I was able to change alll bearings for around $250. So I got lucky and happened to have the rear cover off. Because for a long time, I was trying to save $$ for a new rear diff. Just wouldnt hurt to check it over really good. I had my rear cover off a couple off times not really knowing what to look for. Thankfully I had someone who knew a little more about differentials than I did.
Hope I helped

Jay T

so how do you tell the side bearings are shot?

cole_ford

One way we were able to know if the side(carrier) bearings were bad, was there was a lot of slop side to side with the carrier, and ring gear. In order to do that, you have to pull the diff. cover. When we noticed the slop, we pulled the carrier caps, and dropped the carrier, after pulling the axles of course, and found the carrier bearing on the drivers side was SHOT. I was told I was lucky that the rear end lasted as long as it did.

Since the fix, no clunks, no howling going down the road. Everything good as new again, and it was way less than having a shop do it, or buying a whole new one. But when messing with the backlash kinda sucks. My dad and I had a hell of a time crushing the crush sleeve. Lots of breaker bars. I have a pinion seal leak now, and will bring the truck in to have that fixed cuz its too cold out to try and crush the crush sleeve. Some things are better left to the proffesionals, but if you have the right tools, and some common knowledge of differentials, its not a bad job. All together, my dad and I had only about 3-4 hours into the job. But it sat for a few days, trying to find the bearings. Had to go to Ford.
Sorry so long, hope I helped

cole_ford

But your bump in the back sounds to me like your driveshaft. There have been a few threads on here about the driveshaft going into the transfer case, and how the spline gets worn out, and the only fix is to have the driveshaft rebuilt. I have that same PUSH, that youre talking about, and every 4 months or so, I pull the driveshaft, and lube up the splines on the transfer case with some lithium grease, and Im good to go for another few months. Does the bump do it only when you stop, or go?

Jay T

It does it when I take off. And then only after about 1 revolution of the wheel. So its not right away as soon as I let off the brake. The truck is moving before it ever happens.