D6D Powershift Transmission Disassembly and Inspection

That amounts to 1/3 of the assembly bolts not doing their job. I would be checking for warpage of the cover plate which could lead to complications at the pistons and seals at least for the directional clutches. How long has it been operating this way or was it a sudden failure?. How many hours are on the machine? Do you know any history of the transmission/machine. There are specs for new clutch pack thickness (I don't have info for allowable wear). If there is any suspect as to overall condition now is the time to overhaul the transmission and torque converter. I'd say if the directional clutches inspect good put new bolts (Cat) back in properly torqued to 85 +/- ft. lbs. and put it back in service.

It was mostly sudden failure, I thought I had a fuel or turbo issue, until I realized only forward side was slipping. I am the third owner. The previous owner stopped operating it when he was 92. He did custom work all over the area. He was known for staying ahead on maintenance. And never running it over half throttle. He is not around to ask when the last time the trans was went through. From talking to others it was rebuilt maybe ten yrs ago. The old hour meter stopped working at 9926. He did not replace it. He just kept up with the hours on paper and maintained it by the hrs he logged. It operated a min of 5 yrs without an hour meter. If anybody was ever in the market for a used dozer his was always thought to be the safe bet.

Until further inspection, I am thinking replace all of the clutch pack bolts. And due to slipping occurring after the bolts broke, at a minimum replace disks in #1. But hopefully I can obtain specs for allowable wear.

Thanks,

Tom

It was mostly sudden failure, I thought I had a fuel or turbo issue, until I realized only forward side was slipping. I am the third owner. The previous owner stopped operating it when he was 92. He did custom work all over the area. He was known for staying ahead on maintenance. And never running it over half throttle. He is not around to ask when the last time the trans was went through. From talking to others it was rebuilt maybe ten yrs ago. The old hour meter stopped working at 9926. He did not replace it. He just kept up with the hours on paper and maintained it by the hrs he logged. It operated a min of 5 yrs without an hour meter. If anybody was ever in the market for a used dozer his was always thought to be the safe bet.

Until further inspection, I am thinking replace all of the clutch pack bolts. And due to slipping occurring after the bolts broke, at a minimum replace disks in #1. But hopefully I can obtain specs for allowable wear.

Thanks,

Tom

The actual source of leakage needs to be determined. I suspect there is a problem with the piston sealing rings for at least one side of the direction clutches.

I am thinking that the broken bolts allowed the piston and sealing rings to over extend causing the leak. I should be able to get the directional clutches off tonight.

I don't see that happening without the piston being bent or warped. Piston and sealing rings are the full diameter of the housing.
I'm a ways from 92 but my maintenance has definitely slipped to where I begin thinking it will out last me irregardless.

I pulled the input shaft assembly and #1 clutch pack. The piston and ring and seal looked good. I measured the stack of the three friction disks and two plates with a dial indicator( I did not have a mic). According to the manual I borrowed, the pack thickness is in range of new specs. The friction disks look almost new to me, but I have never seen worn ones. I am going to find a set of mics to make sure.

Right now I believe the leak is coming from the port that is cast through the second clutch pack, then a spacer, then onto the 1st pack. This is where the oil is routed from the valve. It is sealed steel to steel, no o-rings. This port is right between 2 of the broken bolts. So when I used the plexiglass to locate the leak, this port was right next to the opening where the disks and plates are exposed(where I originally believed the oil was leaking). Close enough to be the source of the leak. It was hard to be definite where the leak was at, because the oil was shooting straight in into the glass.

So if the bolts are broke that are supposed to clamp the housings together on both sides of the port, there is nothing to keep oil from coming out between the packs at the port. If I remember right the #1 pack is the only one where the pack port and the corresponding valve port does not directly mate together. This would explain why the other packs are holding pressure.

I will finish tearing it down, inspect gears and bearings, measure all of the plates and disks(replace if needed), reseal it, replace all 9 bolts and torque them correctly.

Tom

Seems you are on it!!!! Any indication of whether or not those are Cat bolts holding the assembly together? Usually Cat has some type of mark on the bolt head. Maybe the were reused and retorqued to often or improperly torqued.
New Cat replacements is the way to go.

Most likely you are correct in reusing the piston rings
The broken bolts will have no bearing on them
Check to see if the clutch packs are all the same (most are)
And switch the 3rd to 1st

Greg