new diff rebuild didn't last more than a couple of tanks

[Rootdown4594]

so i melted my idler gear in my GT. i decided to replace the insides with a robinson steel idler gear and aluminum diff gear and a mip diff rebuild for a b4/t4. i reused the stock out drives. i figured using the diff rebuild for a b4/t4 would be fine but now i don't know. after just one run the diff was pretty gritty. i took everything apart, cleaned it and rebuilt. still gritty. took it out for one more test session and noticed no matter how tight i adjust the diff it would slip. it slipped so much after my second run that now the diff balls have flat spots and i need to rebuild again. i had to run my slipper so loose in order to keep my diff from slipping i knew something was wrong. i also replaced the slipper pad with the newer blue ones. it seems that these newer pads have more grip so maybe that was the culprit. i also used aftermarket diff lube/grease as the mip kit didn't come with any.

i thought i had adjusted my diff to factory specs. tighten diff till the spring bottoms out then back of 1/8 of a turn.

everything seemed fine with the stock diff. i don't know what happened.

[kaiser]

what about the thrust bearing? (the little one in the outdrive)

i find that the thrust bearing is usually the source of the gritty feel. the thrust should be done at the same time you do the diff, sometimes more often.
it's outside the gearbox and get dirtier then the rest of the drive train.

[Rootdown4594]

i completely rebuilt the thrust bearing too. the rebuild kit came with everything you needed to rebuild a diff other than the diff gear. i took the old stock diff balls and replaced the new ones with those. i flipped the new diff rings over and rebuilt the whole thing with the old 10 year old diff balls. it's fine now with the old diff balls. i don't know what i did the first time around. maybe the diff balls made by mip for the b4/t4 are different then the associated ones for a GT1?

[Lonestar]

no matter how tight i adjust the diff it would slip. it slipped so much after my second run that now the diff balls have flat spots and i need to rebuild again. i had to run my slipper so loose in order to keep my diff from slipping i knew something was wrong.

wrong lubricants in the wrong place. you need
- stealth lube on main balls only
- graphite grease on thrust only
sometimes what also happens is some of the thrust fluid gets into the main diff balls and that makes them slip no matter how much tension you put in the diff.

Let us know how it goes
Paul

[adam lancia]

Did you break in the diff before you ran it, or check to see if it worked a little loose during the first run? After I build a new diff I always break it in by holding one wheel and giving it 1/4 - 1/2 throttle for 10 - 15 seconds. Then I hold the opposite wheel and do the same, then check the tension again. It's always much looser after that and requires a snug down. After that's done, I can almost leave it completely untouched until it starts making *those* noises again Good luck!

[Rootdown4594]

everything seems to be fine with the older diff balls. i went to the park and ran it there for a couple of hours with no problems. no slipping at all. if i tightened my slipper too much it would pull wheelies. so it's holding tension. i can visually see the slipper spinning rather then the top shaft if i hold the truck down and give it some gas.

and when i took the diff apart after it started slipping i did notice that the white diff lube was darker than it's suppose to be. so maybe the thrust grease did work its way in.

[Lonestar]

and when i took the diff apart after it started slipping i did notice that the white diff lube was darker than it's suppose to be. so maybe the thrust grease did work its way in.

bingo - that's the unmistakable sign

[Jay Dub]

Ditto to what everybody else has stated. I would also include however that I have never had any luck with MIP diff parts as far as durability is concerned. Stick with the stock AE parts from now on. -Jeff

[Rootdown4594]

i need to rebuild this diff again. are gas trucks more prone to needing diff rebuilds? the diff in my b3 with a 5700kv motor is stock and has never been fully rebuilt just relubed and is still smoooooth. that diff has to be like.... 13/14 years old?

are ceramic diff balls worhty of the price? should i consider them? what about diff rings? do they make harder diff rings? maybe titanium? i'd imagine ceramic diff balls and titanium diff rings would make a bomb proof diff!

[Rootdown4594]

Ditto to what everybody else has stated. I would also include however that I have never had any luck with MIP diff parts as far as durability is concerned. Stick with the stock AE parts from now on. -Jeff

i looked at the mip diff rebuild again and the discription states stainless steel balls rather than carbide. that's probably the issue.

[adam lancia]

Stainless steel balls are no good. Use at least chrome, if not carbide or ceramic.

[Jay Dub]

Heavy duty applications for the most part require carbide. I personally like Ceramic balls. However some people say they have issues with slipping. Never been an issue for me though. The other plus is they are realy inexpensive.-Jeff