M1008 Th400 broken case issue

[pickpocket1982]

All right, first of all I'm not a mechanic. I bought mine M1008 last year from some dealer all right. Ever since trany was leaking. I treated it with those sealant and stuff.. it didn't help. I finally figure out that was transfer case adapter cracked on both sides. It is 208 adapter i guess. So I get adapter somehow from guy who was parting one(thank to this page couse it was kind of hard to find one). And my mechanic replace adapter. Paid $300!!! and then my problems started.. After test drive and drive home, trany starts leaking even worse..I give it back to him. He told me that transmision is cracked by the out put shaft. I didnt wonna spend $1500 so I find one myself..bought books and stuff..rebuild transmision( actually I replace outputshaft from old trany, because the new one was 2WD) Well I struggled a lot with it.. the thing is when I finally put that all together It finally worked perfectly...till I took it on the highway>>and it cracked in the same place as old one!! I dont know what to do now. If it old outputshaft?? Or is it something bend? Engine mounts?? I need another case and a piece of advice.. please

 

[IdahoPlowboy]

There is one here in Idaho on craigslist, but I am sure that is to far away.

 

[86m1028]

Frt shaft could be too long
Do you have the t-case brace on it ?
Bad trans mount ? bad motor mounts ?

 

[pickpocket1982]

Outputshaft is from old trans that was in it..i switch it with the one that comes with it because was too long(from 2WD) so it wasnt too long. I think someone hit on something on the trans mount..and maybe outputshaft itself is bend or something. I replace adapter(t-brace?) but i didnt replace the mount that is bolted to the frame..maybe that is bended?? Does anyone had similar problem??

 

[Westech]

unless your engine mounts are 100% gone (no rubber) there not going to cause a busted case. Your best option is to take that trans out, go to a rebuilder or to the auto parts store and order up a rebuilt unit for 600-700 bucks. Slam the new one in and be done with it.

 

[merace19]

GL broke 2 of mine. The case was split almost all the way around and fluid would dump out. I pulled the case out and gutted it and welded it up. No issues after that. I am cheap and a new case was 200bucks that I didnt have at time.

 

[pickpocket1982]

That what I did..I bouht new one paid $700, it was racing tans I've been told for 500 HP. I just replace outputshaft in it.. And it cracked again..

 

[rnd-motorsports]

did you use the parts out of the 4x4 trans or the 2wheel ? I mean other then the output shaft? the sprag gear if its bad will also crack the case. is the rear driveshaft bent or have a dent in it? the trans will take alot so if you cracked it again there is a major problem with somthing the cross member would be easy to see, if the output shaft in the transfer was bent again you would feel it in the seat when you drive it. LET us know what you find!

 

[pickpocket1982]

I used just outputshaft. But the first tans cracked(all the way around the end of transmission, where the outputshaft is) when i replaced broken adapter..and the second one cracked in the same place..almost the same way. What I'm thinking to do now is I gonna weld broken case, and replace outputshaft with new one. Also Im thinking of replacing trans mount..and i will check that engine mounts(but i think those should be fine it got just 57k miles on it, I guess) Maybe that will help.. if there is anything else I should aware of??

 

[southdave]

isn't there reinforcment bar installed between the tranny and the tranfer case ,on top? also have made sure or spline count ?

 

[466Navastar]

you must have taken your truck to a pretty shady transmission shop - for him to have replaced the adapter and left a cracked transmission in place ....

My guess is GL picked up the truck with a forklift and broke the adapter/transmission and probably bent the driveshaft --which at highway speed....caused unbalanced harmonics to build to the point to where you experienced the highway failure of the new transmission.

if you cant do it - have a driveline specialist look at this truck and tell you what it needs---I wouldnt suggest going back to the original trans shop.

 

[Hasdrubal]

When I got my M1009 it didn't have any of the tranny support braces. My CUCV knowledgeable friend told me the army probably takes them off for whatever reason, then doesn't replace them. He broke his tranny case withought them. Learned the hard way. So I went to a wrecker and sourced them out. There are 3 of them.

 

[doghead]

Was your driveshaft damaged by the vehicle being moved with a forklift? very common issue with GL trucks.

 

[pickpocket1982]

No, how does that reinforcement bar look like, there is nothing I would consider to be a reinforcement bar, would it hold transmission and the box together and align it with each other.
And, I'm not sure about spline count. Outputshaft looked the same but it was just about 1,5" longer, so i switched it :/

 

[pickpocket1982]

You R probably right, it was picked up with forklift :/ I gonna check on that... I'm going to weld shop for now..I gonna put that transmission back together..and we will see :] Thanks 4 the tips U all...U helped me a lot :]

 

[466Navastar]

 

[Hasdrubal]

Sorry guys, its torrential rain here for me to get underneath and take a pic of the braces-support rods. There are 3 of them. 2 shorter ones go from the frame where the motor mounts are to the bottom of the bellhousing. The long thicker bar goes from the block by where the starter mounts to, then goes all the way to the right side of the transfer case. Its mounted with two huge bolts, if you look you'll see the holes for these bolts.

I was told that withought these braces, you'll brake the tranny. So I measured them off, went to a wrecker that only does Chevy trucks, he had quite a few in different lenghts! The longer one I found. The two shorter ones I had to cut and reweld to get the correct length. Cant remember where I sourced out the bolts, I think I bought them new. I did have to borrow a tap to chase the threads so that they threaded in easily.

When it clears up here, I can take pics and post them if you like.

 

[pickpocket1982]

Hello again. So I welded the case, now I'm trying to get output shaft to put trany together and I'm gonna run to drive shaft shop to balance drive shaft or replace it.
I guess output shaft is 32 spline, how long is it?

 

[NPD732]

GM never put the 3 braces on the CUCVS. There is no listing for them in the TMs and all the trucks I haver ever dealt with did not have them. All the civillan models got the braces. Two braces from a plate behind the block motor mount to the lower trans bellhousing. One brace from the bellhousing to the right side of transfer case. There are at least 3 different lengths for the transfer case brace depending on the trans/transfer case combo. I add these braces to all my trucks. Especially my M1031. The 205 is way to heavy not to be supported. Regardless, the braces would not have stopped GL forklift damage. Who knows why GM didn't put them on the CUCV. Maybe it knocked two bucks off the contract price for unit.


I would check the driveshaft, u-joints, crossmember, trans mounts, trans output shaft, transfer case output shaft and transfer case input shaft for damage. My M1031 had a pretzeled driveshaft and the crossmember was bent up about 3/8 of an inch.

 

[ranchhopper]

I had to replace my driveshaft in my 1008 it had a bad vibration at higher speeds. When I took it off there was a tiny ding in it from the forklift thats all it takes to ruin it I couldnt believe thats all it takes to throw them out of phase. I put the new one in and it drives down the road like a new truck. I have worked on several trucks that came from a certain dealer in the chicago area and will say buyer beware they were patched and touched up to appear to be something they werent.