1986 Cat d3b LGP 24y with 3 forward 1 reverse gear, reverse issues!

[JThomas7]

I'm having a problem with my little d3b that's been a great little machine. I bought it knew it was using transmission fluid, I knowing the guy I purchased it from well and he told me it used it the entire time he owned it. I have always put about a gallon in it every 20 hours. I had plans to work on it this winter when we're done with it for the season but here we are.

Yesterday while using the machine to clear some mud and yank out a stuck tractor it all the sudden wouldn't move in reverse. This happened suddenlyl, I had been using the machine for about an hour then all the sudden no reverse. I put it in 1st and back to neutral a few times and then it would creep in reverse until the engine was under a load. I decided to let it cool down and wait until today to mess with it because it is about 20 degrees warmer out today.


When checking it over today it was a little low on transmission oil but not bad, I topped it off with 30wt motor oil. Reverse will work on flat ground until the engines under a load. Hit a steering break and it stops dead in its tracks. The dozer seems to be working fine in all forward gears. I can bury the blade and it will spin the tracks going forward.

I pulled the metal filter out, some minor crud and a small amount of metal flakes could be found. I cleaned it and reinstalled it. It SEEMS like it's a little better but still not right. Also it seems like the transmission oil is a little foamy / air bubbles when I check it. Just seems like the clutch isn't grabbing good in reverse if I had to guess. I'm more of a "parts changer" than a mechanic but try to do most things on my own. I'm hoping that one of you tell me it's something simple but I'm guessing it's not. Any ideas? I have a manual and it looks like it's time to start checking pressure on the valve bodies?

 

[JThomas7]

So no responses yet but I will update this as I go, hopefully someone with some knowledge on these things pops in. I haven't checked pressures yet. I pulled off the belly pan looking for a "Suction screen" that I've read is suppose to be by the drain bolt for the transmission. I see no such thing.

I pulled the floor boards and found quite a bit of dried up oil on top of the valve body for the transmission. I started the dozer and found quite a bit of oil coming out around one of the allen bolts on the left side directly in front of the shift linkage. This bolt was finger tight, I tightened it up and the leak stopped. I thought I would give it a try and see if it was the problem. The dozer seems like it improved about 75 % in reverse. It will back up an incline and now it will almost turn 180 degrees before it bogs the motor down and stops, I can feather the break and get it to turn but it's still not right. Better, but not right. In looking over the valve body area it looks like it has several of these leaks that I need to fix, I'm hoping it's just a combined thing where I've finally just lost too much pressure with all these leaks.

 

[Bob/Ont]

You have fixed most of it already. If you have steering trouble(stopping rather than steering) the clutches might not be releasing when the brakes are on. The only trans screen is the one you cleaned, if it gets dirty the pressure will be too low to release the clutches, it takes 200+Psi to release the clutches. Check at plug in cylinder at hole in side frame by sprocket.
Later Bob

 

[JThomas7]

Thanks for replying. The dozer steers percect in forward. In reverse any time it's under a load is when i'm having a problem. A steep hill or locking one of the steering breaks and it will end up just stopping. It's better by a mile after fixing that. Leak. It's like the clutches in the reverse gear for the transmission aren't grabbing tight enough. It will start turning in reverse then it's like the clutches start slipping in the tranny. The driveshaft quits spinning. Seems to be on the tranny side, not steering clutch side.

 

[Bob/Ont]

You may have a worn out rev clutch pack. The best way to tell if it's a slipping clutch in the trans or a steering clutch not releasing is to listen to the engine speed when it stops driving in reverse. Press down hard on the center brake pedal and shift into forward 2 or 3 and observe the engine speed looking for a change. If it goes down you likely have a slipping clutch if not you may have a steering clutch release problem.
Later Bob

 

[JThomas7]

Engine defintely drags down some. Sure seems like it's the drive clutch slipping in reverse. Just can't figure out why it wouldn't slip going forward. Also when I check the transmission dip stick I'm still getting a lot of air bubbles.

 

[Bob/Ont]

Are you running at full throttle? The steering needs lots of pressure to release, the pressure comes from the trans pump, if reverse clutch is leaking it could lower steering pressure. Maybe get some seals and replace all on the pump pickup side, from screen to pump and from pump to valve. Picking up air will make foam.
Later Bob

 

[JThomas7]

I will definitely try to reseal those areas, seems straight forward enough.
On flat ground it will move in reverse at just about anything over 1/4 throttle. At full throttle I can backup and if I let it get up to speed first it will spin almost 180 degrees before it stops moving, I can release the steering break, let it start moving again and can usually pedal it 2 or 3 times to complete a turn. If I go from neutral to reverse with a steering break locked in the engine will rev down a small amount and nothing will happen.

If we take steering out of the occasion it can't even back up inclines it could before. It can operate on flat ground decent enough but even simple black blading is dragging it down until it will stop. If the drive trains not under a load it will reverse and go up slight inclines but that's about it. I realize this could mean that this could still mean the steering clutches could be slipping and not the transmission clutch, but if the transmission clutch was grabbing and the steering clutches were slipping wouldn't the drive shaft still be turning out of the back of the transmission? I can back blade on flat ground and if I drop the blade to the point of picking up the front end and try to back up the driveshaft won't even spin.

Seems like if they were locked together it would go all day long in a straight line but wouldn't turn, if they were slipping it would probably do what I'm explaining but the driveshaft out of the back of the tranny would be turning?

 

[Bob/Ont]

I think from what you have said so far the reverse clutch in the trans is slipping. You may find more clutch material in the big screen. If you rebuild the trans get the cooler in the bottom tank of the rad cleaned out too.
Later Bob

 

[JThomas7]

Any reccomendations on a good place online to order a reverse clutch pack? I had a buddy over today who was a former cat mechanic. We checked all pressures and everyone was pretty mich exactly what the book called for. We're to the point where all it can be is the clutck pack.

 

[Nige]

A lot of people here have had good luck with Offroad Equipment when buying parts for older Cat machines - www.offroadeq.com/