M1078 A1 transfer case

[wheelspinner]

From what I understand the upgraded C6 thrust bearing is a simple drop in…..

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?

Since starting to research this now, I wonder the same thing. If you have access doesn’t look like a tough swap/retrofit preemptive to a failure if it truly eliminates a failure point

 

[BERZERKER888]

after spending a solid 45 minutes "engineering" the simplest most efficient way if repositioning the crossmember.... sawzall and reweld ...
crossmember had 4 Huck bokts in passenger side, 1 inch from the fuel tank ...drivers side , I believe 2 huck bolts and 2 grade 8 bolts.. The driver's side will need the battery box , air tanks and air dryer removed...and let's not forget the mid pipe and muffler come down as well. ..with all of those listed items removed you can only slide the crossmember to the rear approximately 6 to 8 inches from what I can tell before another group of Huck bolts stands in your way. the other alternative is to notch the frame and drop the crossmember down that way.....

and let's not forget notching the bed frame above the housing ..

and should the above-listed steps be successful, the next C6 clutch housing million dollar question will be can the clutch assembly be disassembled while still mounted to the transmission.
I think it just might..

and for those scratching thier heads as to why I am going through all this, my truck is currently beached in the middle of a field on typical Florida sugar sand. so dropping the transmission and transfer case in one assembly is virtually impossible....

on a bit of better news, no bearing remnants found near the speed sensor , tranny fluid or filters...a $10 expanding pencil magnet helped immensely

 

[langstonhs]

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?

FYI, the C6 housing is more than just a cover. The C6 clutch parts (including the clutch plates and the broken bearing) are sitting inside it. Maybe a few pics will help.

IMG_0485: As the C6 looks when it is removed from the TC. The drive hub sticks up in the middle, and when it is mounted, slides into the TC a little ways. See the last pic.
IMG_0489: Retaining ring
IMG_0490: Backplate (looks like a clutch plate, but a lot thicker)
IMG_0493: First friction plate (the 5 friction plates alternate with the 5 reaction plates)
IMG_0498: Hub removed, you can see the springs underneath, and sitting on the springs, what was left of the bearing
IMG_0507: What is behind the C6 clutch housing. You can see the shaft sticking out. Keep in mind, the drive hub slides further in on the shaft than the mounting surface of the C6 housing.
IMG_0509: With the bearing retainer removed.

 

[coachgeo]

...

and for those scratching thier heads as to why I am going through all this, my truck is currently beached in the middle of a field on typical Florida sugar sand. so dropping the transmission and transfer case in one assembly is virtually impossible....

on a bit of better news, no bearing remnants found near the speed sensor , tranny fluid or filters...a $10 expanding pencil magnet helped immensely

congrats on not finding reminents of bearing in places you looked.

IMHO... remove rear axle shafts..... remove front drive shaft.. tow it out of the field to a better place....

 

[Ronmar]

Excellent pics! The clutch pack is inside that C6 housing, secured with that large snapring. It slides over the end of a long shaft(seen in the last 2 pics) that runs forward thru the transfer case, thru the hollow transmission output adapter shaft that couples transfer to trans output(P3 planetary carrier) and thru to connect to the sun gear of the P3 gearset.

It’s purpose, using the C6 clutch which is configured as a brake(couples shaft to housing), is to hold the P3 sun gear in place. That gives us that super low 1st gear and the 3070/3700 series 7 forward speeds Instead of the 6 forward speeds found in the base 3060 transmission.

That long shaft is also the reason we cannot pull the transfer case off of the transmission while still on the truck, in the limited space allowed… You have to move the transfer far enough to the rear to clear that shaft which protrudes 2-3” behind the transfer case…

I am glad you took pics of this Langstonhs, thanks for sharing…

 

[coachgeo]

congrats on not finding reminents of bearing in places you looked.

IMHO... remove rear axle shafts..... remove front drive shaft.. tow it out of the field to a better place....

also.. how hard/crazy would it be to remove engine and tranny mounts, drive shafts,,, some fan shrouding and other things neccissary to lift the nose of the engine tranny combo up.... with a cherry picker above or jacks down below... thus lowering tail end of tranny down..... to gain easier access to this?

 

[BERZERKER888]

congrats on not finding reminents of bearing in places you looked.

IMHO... remove rear axle shafts..... remove front drive shaft.. tow it out of the field to a better place....

therein lies another rub. When I drove the truck to my home for good long look before discovering the bearing failure, which I hope is the cause for the " grumbling howling" sounds upon deceleration, within minutes the jack booted Gestapo thug HOA was on the phone, thus negating a " home repair". Thus returning the truck to the field where it currently resides. My saga continues..

 

[BERZERKER888]

also.. how hard/crazy would it be to remove engine and tranny mounts, drive shafts,,, some fan shrouding and other things neccissary to lift the nose of the engine tranny combo up.... with a cherry picker above or jacks down below... thus lowering tail end of tranny down..... to gain easier access to this?

a possibility for sure....

 

[coachgeo]

... Gestapo thug HOA ... My saga continues..

grrr. I pray my luck continues in this arena.... Im on a dead end gravel alley that even people whom have lived in this town for decades do not know even exist... so no one bothers me and my junk... Am waiting for murphy to change that while praying it does not.

plywood and tarped ground?

PS- more than once friend and I unbolted bed and pulled it back a good bit. Maybe build temp. legs for end of bed to stand on as you pull it back 1/2 way. then you can do like another has and put cherry picker on the chassis above ... use the tranny lifting eye (TM shows how to make) and see if you can combine all the above ideas to tilt the tranny/engine combo enough to pull that where she sits. Make sure it is chocked well... that is a total weight you want to know is fully secure and then some

 

[Ronmar]

I think the problem you would run into with tilting engine/trans to remove the C6 housing is that lower crossmember. It still might not clear that and you would be approaching an angle where the rear of the engine contacts the lift structure to even clear the upper crossmember….

Langstonhs pics tell the tale quite clearly. The Main-shaft protrudes 2-1/2 inches out the back of the transfer housing. The splined collar of the C6 clutch-pack carrier protrudes forward of the clutch housing at least 1-1/2” so you could need nearly 5” of clearance. As it stands there is about 2-3/8” of clearance between the C6 housing and the subframe/upper Crossmember. if it could be moved to the rear 3” or the center of it removed you could get the C6 assembly off of there…

The transfer case needs to move to the rear at least 10” to clear that center shaft. Not something I would want to do with a tilted assembly and a #500 transfer case. Now if those two crossmembers were removed, I think it would be very doable. If you left the ends of the upper subframe crossmember as tabs, it could be converted to a bolt-in(Next larger size of channel to slip over and interlock with the stubs lect behind) and Since the lower is already a bolt-in, it might could be converted to a 2 piece bolt-in…

 

[coachgeo]

I think the problem you would run into with tilting engine/trans to remove the C6 housing is that lower crossmember. It still might not clear that and ....

well drat... blew that idea out of the water... crawling back into my corner now.

 

[coachgeo]

well drat... blew that idea out of the water... will crawl into a corner now lol

 

[BERZERKER888]

I think the problem you would run into with tilting engine/trans to remove the C6 housing is that lower crossmember. It still might not clear that and you would be approaching an angle where the rear of the engine contacts the lift structure to even clear the upper crossmember….

Langstonhs pics tell the tale quite clearly. The Main-shaft protrudes 2-1/2 inches out the back of the transfer housing. The splined collar of the C6 clutch-pack carrier protrudes forward of the clutch housing at least 1-1/2” so you could need nearly 5” of clearance. As it stands there is about 2-3/8” of clearance between the C6 housing and the subframe/upper Crossmember. if it could be moved to the rear 3” or the center of it removed you could get the C6 assembly off of there…

The transfer case needs to move to the rear at least 10” to clear that center shaft. Not something I would want to do with a tilted assembly and a #500 transfer case. Now if those two crossmembers were removed, I think it would be very doable. If you left the ends of the upper subframe crossmember as tabs, it could be converted to a bolt-in(Next larger size of channel to slip over and interlock with the stubs lect behind) and Since the lower is already a bolt-in, it might could be converted to a 2 piece bolt-in…

View attachment 838662

curious how high must the 1078 be lifted in order to drop the TC/tranny from the bottom..? or is the unit removed from the top?

 

[BERZERKER888]

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

My transmission s/n is ”prior” as shown in your red circle…..necessitating the upgraded composite thrust bearing????, but a parts search via Allison reveals the replacement is the same “ defective” bearing….hmmmmm. Is there a difference in transfer cases between then A0 and A1 versions ?

 

[Ronmar]

That was the point I was trying to make, the info I posted draws attention to that specific bearing as being an issue, but it only says to simply insure you replace it, not that their is an upgrade, as the specified p/n still appears to be valid and available, unlike the info Langstonhs posted showing the P/N in his S/N range has been superseded. The P/N of that part on the bulletin is also different than that listed in the 24P manual. since the P/N is different between the 24P and that bulletin, I suspect somewhere along the line Allison did some R&D to try and resolve this weak link in the design.

We will need to contact Allison with our S/N’s to determine if the composite thrust washer/updated part applies to us.

The A0 and early A1 used the MD-3070PT transmission. Somewhere in there Allison re-designated the AWD 3070 as the 3700 which I believe was used in the A1R. I am sure there are some changes, but I believe they are basically the same transmission as I occasionally see them used in the same breath as far as applicability. The Tech Bulletin Langstonhs posted a pic of, is yet another example of this(applies to 3070/3700 Transmissions). They also use the exact same gear ratios…

 

[BERZERKER888]

more pondering has left me with the “mature” option that it would be better for my TC/ tranny impending doom noise to be diagnosed by a Allison technician with experience in all variants of the 3070 family before I take then Sawzall or plasma cutter to task…

 

[BERZERKER888]

smart money says replace the transfer case /transmission ...the quandary now lies with finding a good used unit and not buying another bum transmission... other wise MTP has retran units available for $10k

 

[aw113sgte]

I think the problem you would run into with tilting engine/trans to remove the C6 housing is that lower crossmember. It still might not clear that and you would be approaching an angle where the rear of the engine contacts the lift structure to even clear the upper crossmember….

Langstonhs pics tell the tale quite clearly. The Main-shaft protrudes 2-1/2 inches out the back of the transfer housing. The splined collar of the C6 clutch-pack carrier protrudes forward of the clutch housing at least 1-1/2” so you could need nearly 5” of clearance. As it stands there is about 2-3/8” of clearance between the C6 housing and the subframe/upper Crossmember. if it could be moved to the rear 3” or the center of it removed you could get the C6 assembly off of there…

The transfer case needs to move to the rear at least 10” to clear that center shaft. Not something I would want to do with a tilted assembly and a #500 transfer case. Now if those two crossmembers were removed, I think it would be very doable. If you left the ends of the upper subframe crossmember as tabs, it could be converted to a bolt-in(Next larger size of channel to slip over and interlock with the stubs lect behind) and Since the lower is already a bolt-in, it might could be converted to a 2 piece bolt-in…

View attachment 838662

Was looking at my 2007 A1R MTV today requarding this and it doesn't have that same brace... almost looks like the housing could come off just by moving the trans aux cooler lines.
Not sure if it has the updated sleeve bearing or not.

 

[InvictusDecretum]

Was looking at my 2007 A1R MTV today requarding this and it doesn't have that same brace... almost looks like the housing could come off just by moving the trans aux cooler lines.
Not sure if it has the updated sleeve bearing or not.
View attachment 906904

My 2002 A1 also does not have the brace mentioned earlier. No current issues but I am looking into pre-emptively replacing it. Trying to find a place to buy the new P/N 29545936 is proving difficult. Waiting on a callback from my local Allison dealer but not sure Allison even makes this anymore.

 

[Ronmar]

yep, those P6 assemblies should come right off without that crossmember. i got a quote from Allison for $430 for that composite washer. At that price I am tempted to engineer and machine my own...