7040 Ring and pinion gear

This is a rare and unfortunate failure. Replacing the ring and pinion in one of those is not for the faint of heart. Big job to say the least. Move the wheels out, Fuel tanks off,floor out, oil out,disconnect hydraulic lines and cables, support the rear of the cab,remove the rear cab mounts,split the tractor and the start tearing it down. Hydraulic valve stack off,lift chest off,both final drives off, differential lock valve off,numerous internal lines and fittings to remove, both brake assemblies off. You need to support the differential assembly as you remove the brakes. There is a nut on the front of the pinion that has to come off. I believe that the range shift fork and cover has to be removed too. Top counter shaft out also. The pinion shaft then presses out the rear. A factory service manual and several special tools are really needed. Good used parts shouldn't be a problem because of rarity of this problem. Numbers are etched on the pinion and there's a number stamped in the rear end housing to aid in setting up the assembly. I would probably remove the hydraulic pumps too before I split it and I prefer to crib up the rear end and remove the rear tires or wheels before taking the final drives off. Did I mention that it was a big job. I recall putting a new set in a 7060 once and on another 7060, we just got a complete rear end assembly from salvage and rolled it in. If you did that, you could use a 7060 rear end assembly and gain the 4 pinion spider gear setup. I'm probably forgetting a lot of small details here,but that's about the jest of it.

Makes me wonder if this tractor fell into that serial number group that had loose ring gear bolts back in 1976/77 and actually failed the bolts themselves by shearing them all off. Anyway, I'm not there looking at the carnage, but do know that if it was at my place with a decent looking pinion, it would just get the ring gear replaced and I would lose no sleep over it. Back in the early Spring of 1976, I had a D15/s2 apart to replace 3rd gear and related jump out parts. It had a piece of a pinion tooth missing, so my boss had me replacing the ring and pinion gear set, because that's how they were sold....a "matched" set. I was 22 at the time and this was my first tranny/rearend job and I missed the part where I needed to order new bolts and nuts for the ring gear, as the old ring gear was riveted onto the differential carrier. Time was working against us as spring tillage needed to be done and it was a Friday with Saturday being a working day for the shop. Between my boss and I, we decided to use the old ring gear to get the job done. Worry about noise from mismatched gears ???? NO WAY because every D-15/s2 I ever drove howled like he77 in road gear anyway !!! How bad could it be ?????   Well, it was amazingly QUIET in road gear  !!!!  So, over the next 20 years I had two more D-15's that got the same treatment with the same exact results !!!   I would use another 7040 ring gear against a good pinion and feel fine about doing so. Caterpillar sells pinions and ring gears SEPERATE in their old D5/D6 etc dozers. No matched sets there.

I had a pinion bearing fail on my m100allis grader a couple years back ,pinion was not good but I thought ring was still good enough to use again,considering the amount work the machine did,but wrecker would not sell me just the pinion,said matched set or nothing. Was a hell of alot of extra work ,preloading and such compared to just swapping pinion.

As stories go about this particular area,I also remember the mid seventies loose ring gear bolts campaign. If they backed out to much, they destroyed the live PTO drive shaft. Seems like we had to pull out some differential assemblies if it broke the carrier or differential lock cover plate. Otherwise, the repair could just be done through the top if nothing else was broken. New bolts were used that had a larger head and serrations under the head plus loctited. We made some special wrenches for torqueing the bolts. We had a whole bin full of those old bolts when that update was done. The factory implemented some new torque tightening procedure after that mess. I believe that there was another, separate issue, where the ring gear bolts were to hard and brittle causing them to just break. They had that narrowed down to a specific group of tractors that needed checked. I don't remember if those were maroon or black belly tractors. Regardless, if the bolts broke off in the ring gear, it was a challenge to get them out without pulling the whole assembly out. We inserted a large roll pin through the differential cover plate and carrier. We then bent a welding rod at a 90 degree angle and stuck in through the roll pin. While holding the welding rod in place, someone else would turn on the welder briefly. We were able to stick the roll pin to the broken bolts with the weld and get them out. It worked surprisingly well. I also seem to recall that the early tractors had a running change from maybe 1/2 inch bolts to 9/16 hardware??

For all that I think I'd be looking for a salvage assembly and swap it in....

As I understood it, A-C ate everything. House of Screws probably offered to pay for the bolts and that was it. It was a bad deal regardless.