M1078 A1 transfer case

[MrMikey4026]

This, I hope, is the final post on our transmission failure.

When we discovered that the C6 thrust bearing came apart inside the transfer case, we decided it was necessary to take apart the whole transmission to see where the bearing parts went, and if there was any additional damage. Once done, we were relieved to find that the damage was exclusively in the C6 clutch, and that the rest of the transmission looked to be in great shape. We figured there were approximately 40 roller bearings floating around somewhere in there, and we found about 3 of them in the C6 clutch, and another 30-something in the screen on the intake side of the scavenger pump. This screen is behind the elbow that the hose of the scavenger pump attaches to at the side of the transfer case.

We have a Stewart & Stevenson in Albuquerque, but they did not prove to be very helpful for military truck parts. However, they are also the Allison transmission distributor, and were very helpful in ordering the parts we needed for the transmission. They printed out all the parts diagrams and parts lists for the transmission after we gave them our serial number, and we were able to order replacement parts based on these lists. Xcalliber Transmission online also sold us some of the parts we needed; one part was used (the C6 clutch cover/housing), some were new Allison parts, and others were aftermarket, but made by Xcalliber. Allison genuine parts can literally cost a fortune, so we were happy to have an alternate source for them.

We put the truck back together yesterday and took it for a drive, and it seems to shift through all the gears just fine, with no error codes. We had never taken apart any transmission before, much less an automatic of this size, and used the TMs to do the work. We did have to buy a big transmission jack, a big engine stand, and a big impact wrench to do the job, but we like that better than paying for someone else's labor. Thanks to everyone on here who steered us in the right direction.

Great job, these transmissuons are not for the weak. They always leave you with a bit of satisfaction, because you fixed it and it worked.

 

[BERZERKER888]

and I too have joined the phantom bearing explosion..https://photos.app.goo.gl/EKVtaCu7xFtM4KPj9


and unfortunately I do not have the mechanical aptitude for a tear down/reassemble that the original poster has .. therefore I am in need of a tranny/transfer case unit in good working order as well as a competent technician to do the swap out in the central Florida area ..

 

[simp5782]

and I too have joined the phantom bearing explosion..https://photos.app.goo.gl/EKVtaCu7xFtM4KPj9


and unfortunately I do not have the mechanical aptitude for a tear down/reassemble that the original poster has .. therefore I am in need of a tranny/transfer case unit in good working order as well as a competent technician to do the swap out in the central Florida area ..

Do you have an A0 or A1 truck? 2 totally different transmission setups.

 

[langstonhs]

Do you have an A0 or A1 truck? 2 totally different transmission setups.

We used the TMs on this website to do the transmission repair, which I think are for the A0, and we have an A1 truck. There were some differences, but the TMs still worked for us.

 

[BERZERKER888]

We used the TMs on this website to do the transmission repair, which I think are for the A0, and we have an A1 truck. There were some differences, but the TMs still worked for us.

1995 S&S 1078 AO.. as for the TM, I've had a heck of a time trying to figure out which TM is applicable to my transmission/transfer case woes .. can you please send me the file or link to the specific TM...thanks much

 

[langstonhs]

M1078 TM's

Listed below are a number of the TM's for the M1078 trucks. To save them to your computer, right click, select "save as" m1078_TM 9-2320-365-10.pdf TM 9-2320-365-10 for the M1078 series trucks. m1078_TM 9-2320-365-20-1.pdf TM 9-2320-365-20-1 for the M1078 series trucks. m1078_TM...

www.steelsoldiers.com

I got there by clicking "TM" at the top of this website, then navigating to "Present Conflict Vehicles TMs" and then to "M1078 TM's".

But here are my notes on where this stuff can be found:

Where the rest of the lost roller bearings probably are (and you'll probably want to find them so they won't cause you problems later):
TM 9-2320-365-24P, Figure 128, “SCAVENGE PUMP, HOSE AND FITTINGS”, and page 128-1, item #7

Removing and replacing the C6, including bolt torque specifications:
TM 9-2320-365-34-2: Section 22-3 “TRANSFER CASE MODULE REPAIR”, pages 22-6 through 22-9, steps 1, 2, 12, and 13

Disassembling the C6 clutch pack:
TM 9-2320-365-34-2: Section 21-14 “C6 CLUTCH HOUSING ASSEMBLY REPAIR”, pages 21-66 through 21-69
Note that the thrust bearing in the diagram on page 21-66 is obsolete.

C6 parts diagram:
TM 9-2320-365-24P, Figure 130, “TRANSFER CASE MODULE (SHEET 3 of 4)”, and corresponding part numbers on pages 130-2 through 130-3

 

[simp5782]

We used the TMs on this website to do the transmission repair, which I think are for the A0, and we have an A1 truck. There were some differences, but the TMs still worked for us.

I was referring to what transmission he needed for the replacement since a base model is a WTEC 2 and an A1 is a WTEC 3.

I can have the whole assembly out and on the ground in around 45minutes. It's pretty simple. You shouldn't need a TM honestly.

 

[langstonhs]

If you give your transmission serial number to the Allison dealer in your area, they can print you out the applicable transfer case diagrams and parts lists from their parts catalog.

 

[langstonhs]

I was referring to what transmission he needed for the replacement since a base model is a WTEC 2 and an A1 is a WTEC 3.

I can have the whole assembly out and on the ground in around 45minutes. It's pretty simple. You shouldn't need a TM honestly.

Ha. Well. We didn't have any transmission repair experience and needed the TMs. Of course there are better people out there. We just didn't want to pay them, and weren't afraid to try. Without the TMs, we wouldn't have.

 

[langstonhs]

I think I should note that if your C6 clutch cover was damaged on the inside as ours was, it could take a lot of work or money to get a replacement. Allison could probably get you one pretty fast, but they want a fortune for it ($2000+). We found a used one from Xcalliber for $700+, but I think they only had one. You might be able to get one off a junk transmission somewhere for cheap. Going to our local Allison dealer and giving them our transmission serial number was a real help. They printed out and gave us the parts diagrams and parts lists for our transmission, so when we found we needed to replace a part we had the right part number to search for, both at Allison and online.

 

[BERZERKER888]

based on the parts diagrams...the thrust bearing seems to be the culprit behind all my grief..the "new/improved " version is $250..ouch..(through Allison)..part #7 on page 21-66....I'll check the screen "filter" as mentioned in -24P tomorrow.... I assume that is the shared oil line with the tranny..so , hopefully any pieces/parts of the grenades bearing will reside there...
As a side note, aside from the apparent death sounds from the transfer case.. the tranny shifts smooth and I have no codes...mode switch to low works as well...
smart money says to not take any chances and swap out the tranny/TC as one unit a used unit...but my hesitation lies with replacing the damaged unit with another damaged unit... I've contacted Xcaliber and Momma Allison here in Florida for alternative solutions..
Looking back would you now have considered just replacing the entire TC unit?

thanks

 

[langstonhs]

based on the parts diagrams...the thrust bearing seems to be the culprit behind all my grief..the "new/improved " version is $250..ouch..(through Allison)..part #7 on page 21-66....I'll check the screen "filter" as mentioned in -24P tomorrow.... I assume that is the shared oil line with the tranny..so , hopefully any pieces/parts of the grenades bearing will reside there...
As a side note, aside from the apparent death sounds from the transfer case.. the tranny shifts smooth and I have no codes...mode switch to low works as well...
smart money says to not take any chances and swap out the tranny/TC as one unit a used unit...but my hesitation lies with replacing the damaged unit with another damaged unit... I've contacted Xcaliber and Momma Allison here in Florida for alternative solutions..
Looking back would you now have considered just replacing the entire TC unit?

thanks

Who knows, you might have witnessed the bearing fail before any other damage was done. That would be great. But I don't know any way to be sure but look. That's why we just took the whole thing apart.

But I don't regret the rebuild. We learned a lot and now have a lot of confidence in the transmission and transfer case. There was no used unit in my part of the country anyway.

 

[BERZERKER888]

Who knows, you might have witnessed the bearing fail before any other damage was done. That would be great. But I don't know any way to be sure but look. That's why we just took the whole thing apart.

If I had this happen again on a different truck I would probably try to fix the C6 on the truck by removing the frame cross-member, remove the c6 clutch and fix anything broken in it, and put it back together to see if my problems went away. But I don't regret the rebuild. We learned a lot and now have a lot of confidence in the transmission and transfer case. There was no used unit in my part of the country anyway.

thanks much for your insight ... tomorrow I will pull the filter screen... and pray.

I'll keep you posted.

 

[Ronmar]

Who knows, you might have witnessed the bearing fail before any other damage was done. That would be great. But I don't know any way to be sure but look. That's why we just took the whole thing apart.

But I don't regret the rebuild. We learned a lot and now have a lot of confidence in the transmission and transfer case. There was no used unit in my part of the country anyway.

Was the thrust bearing that failed in the C6 assembly, part number 7 in this diagram? Was looking at the note in the A0 TM about replacing it specifically, when you had the C6 cover/assembly off, on transmissions prior to a particular s/n… If it was identified as an issue back then you would think they would have resolved it before transmissions manufactured in 2011…

Since you have pulled the C6, how much clearance is needed to pull the C6 assembly? IE can it be inspected/replaced preemptively in the space available with the trans installed?

 

[Ronmar]

And I guess a question for Allison would be, since that bulletin Langstonhs posted starts with a particular s/n transmission, does this roller to composite washer change apply to earlier s/n units used in the A0?

The roller bearing p/n listed in the 24P manual still shows as being available from various suppliers…

 

[langstonhs]

And I guess a question for Allison would be, since that bulletin Langstonhs posted starts with a particular s/n transmission, does this roller to composite washer change apply to earlier s/n units used in the A0?

The roller bearing p/n listed in the 24P manual still shows as being available from various suppliers…

View attachment 838475

This is why I advocate giving Allison your particular transmission serial number and getting the transfer case parts list for your particular truck. When you re-order the bearing part, they should automatically give you the thrust washer if it applies, as they did with us.

 

[langstonhs]

Was the thrust bearing that failed in the C6 assembly, part number 7 in this diagram? Was looking at the note in the A0 TM about replacing it specifically, when you had the C6 cover/assembly off, on transmissions prior to a particular s/n… If it was identified as an issue back then you would think they would have resolved it before transmissions manufactured in 2011…

Since you have pulled the C6, how much clearance is needed to pull the C6 assembly? IE can it be inspected/replaced preemptively in the space available with the trans installed?

View attachment 838470

That's the one.

There is not room to remove the C6 clutch housing while the transmission and transfer case are in the truck, apart from removing or modifying frame components that are in the way.

 

[BERZERKER888]

That's the one.

There is not room to remove the C6 clutch housing while the transmission and transfer case are in the truck, apart from removing or modifying frame components that are in the way.

I agree.... after taking a good long looky loo at which frame components stand in the way of removing the TC without removing the tranny, you may have had the right idea .... a grinder on the cross member, Huck nuts after dropping the air tanks and a cut off wheel/plasma cutter to a relatively small portion of the bed frame....just maybe it would work saving me a ton of grief....but getting enough leverage on the upper bolts which hold the TC to the tranny presents another roadblock..

 

[Ronmar]

Yea, I don’t have a bed on mine and my upper subframe is going to be converted to be the floor structure of my hab build so it is mostly unbolted Already. I might slide that upper frame back so I can pull that c6 cover and inspect/replace that bearing just because I can. It doesn’t seem to be a terrifically high failure item, but while I can get at it fairly easily on mine, I might as well…

 

[BERZERKER888]

Yea, I don’t have a bed on mine and my upper subframe is going to be converted to be the floor structure of my hab build so it is mostly unbolted Already. I might slide that upper frame back so I can pull that c6 cover and inspect/replace that bearing just because I can. It doesn’t seem to be a terrifically high failure item, but while I can get at it fairly easily on mine, I might as well…

From what I understand the upgraded C6 thrust bearing is a simple drop in….if that’s the case, fighting with 8 Huck bolts , moving the crossmember and maybe a little nip/tuck in the bed frame rails with a plasma cutter will grant enough access to the thrust bearing… is it possible to remove/inspect/service the C6 clutch pack once the C6 cover is removed while still mounted to the tranny?

is it at all possible that my suspected C6 thrust bearing death is causing my transfer case to grumble/grind/howl while off the gas and decelerating?