Front differential not staying engaged

A 2005 Chevrolet K2500HD, It has the 6.0/4l85E and manual select transfercase.......
The transfer case and transmission is Brand new, I had the dealer install it last week...... before that, We have had the transfercase, and front Diff pulled and gone through, or replaced, at least 6 times..... of those at 2 different dealerships...... Between both Dealerships, Every part in the front differential has been replaced, we have a brand new transfercase, and the 4 wheel drive still will not stay engaged when the truck gets into a hill............. So, with a brand new transmission, transfercase, a basically brand new front differential,(everything but the housing) Why is it not staying engaged in 4x4 when a load is put on it? When I say it will not stay engaged, It goes in, and acts okay, until you get into the mud(even a slippery road) It starts to pop...... sounds kinda like a ratcheting sound.......... If we cannot fix it, Its going to be auctioned off..........(when I say we, It is a Mine vehicle).... It will do it on a flat road that a water truck has recently watered......

is the shifter accually moving out of 4wd or is it just doing it thought the transfer case?

The transfer case is staying engaged..... Its the front differential that is not staying locked in...... It has had 5 new actuators put in....... A side note, The 2 dealers we took it to, both asked us not to bring it back, cause they have both had it apart 3 times, and they cannot find the problem....

Those trucks have auto locking hubs, so when you mean not staying 'locked in' is it the wheels or the differential?

yeah that could be a good cause.. i would get some warn manual locking hubs for it..

that, im not sure.... but the whole front end has been rebuilt..... im talking every possible part......and, on chevrolets, where they have ifs, would the hub assembly not be included in the front diff???? the cv axles drive the hub assembly.......

I dont beleive the hubs are considered part of the front differential. I know you can replace and rebuilt the hubs without touching the differential so I am leaning towards no...

ive pulled the front end apart, and never found anything but the wheel bearing/hub assembly, which the splines of the cv axle drives...... so unless the cv axles bolt to a hub assembly......... im thinking that the electronic actuator in the front diff is what engages the hubs...... thats why they make the cable actuators that engage the hubs that replace the electronic actuators..... ill have to look in the manual tonight....

yeah i can give you a definite no... i was under the assumption that is was a solid axle truck... you can still get a set of manual locking hubs for it..

When you say every part are you talking about the front carrier as well? When it pops out of 4x4 does it go back in on it's own? Also when they say that Tcase was replaced did they show you the new case vs. the old? Or did they just take the OEM case apart and check the internals? It sounds to me like the syncro on the planetary is bad and that is a part that can easily be overlooked when rebuilding a tcase... The syncro has a clutch disk that when the lever is pulled is engages the clutch in the planetary and locks the tcase in 4x4... If the clutch pad is slipping it will cause the 4x4 to feel like it disengages when really it's the tcase... Now does it do this in 4hi and 4lo or is it prejudice to one or the other?


Sorry I can't be of more help this is just like a problem I recently encountered when rebuilding a friends NP208 and thought I'd share my findings.

When I say everything is new in the front differential, Its EVERYTHING.......... and transfercase is brand new as well. they tried to rebuild it Twice, and when it wasnt staying in, they ordered a new Tcase for us.......... And yeah, When it "pops" out of 4 wheel, theres a loud clunk, that is felt, and heard, and then when you let off the gas, It reengages and then will do it again....

Well, Here's the verdict....... Its being sold At auction to the highest bidder( its a company auction to employees)....... No one wants it due to the 4x4 not working, and its a pain..... Im thinking where it has a brand new trans, and transfercase, and the 6.0 is running good, I may go find me a solid front axle, and make myself a 2005 K2500 with a solid axle......... Im thinking I can walk away with this truck for about 1200 dollars or so, and everything works really well under it(it should, its all brand new)..........

well there you go... then once you solid axle it sell it back to you company for 10,000 and you would have a pretty nice paycheck.. lol

so, a thought came to me last night... the front diff housing was cracked, they sent it to a shop downtown, and the shop found the gears messed up..... they replaced the front and didnt touch the rears.. now, if the idiots at the shop(the cheapest, not just price) put the wrong gear ratio in the front, would it not be a clunking noise and feel?

batty1214 wrote:

so, a thought came to me last night... the front diff housing was cracked, they sent it to a shop downtown, and the shop found the gears messed up..... they replaced the front and didnt touch the rears.. now, if the idiots at the shop(the cheapest, not just price) put the wrong gear ratio in the front, would it not be a clunking noise and feel?

That would do it. The clunk would be the hubs slipping to allow the tires to match speed. Does make sense...

Only one way to find out, pull the differential cover and start counting.