New to the group but looking for direction. Thanks in advance. We have encountered an issue with our farm dozer. The transmission pump spur gear Part #7S8621 (i guess that's what I would call it) has about 1/3 of it's 59 teeth ground off. I have never seen this and our shade tree mechanics around are at a loss as well. Cat does not make this gear anymore and it doesn't come with the transmission pump group. I have searched dismantled machines around but no luck. Has anyone experienced this situation or know someone that has? We have examined the gear inside the transmission with a lighted camera and it looks fine. Any help would be appreciated.
Was the tractor ever parked at some point in its life for an extended period of time.? There appear to be a number of different sources (aftermarket I assume) on the internet for the 7S8621 Gear even though Cat has discontinued it.
We have been using the dozer since 2011...not everyday, but fairly regular. Prior to that, it was a working backup for a dirt moving company. I have talked to several online sources but nothing has come of it. They have the pump but no gear...or the gear has 60 teeth. I had a couple of leads in China but I couldn't get pictures for comparison. I kinda wish I knew why the teeth ground off and if I have another problem? Thanks for the feedback.
Although I don't doubt what you say regarding having inspected the gear inside the transmission case that drives the pump gear I can't see any way that it will not have suffered at least some damage. If it is so hard to locate a transmission pump gear I think it would be unwise to simply replace that one gear without pulling the transmission apart (or using a borescope) to at least inspect and confirm the condition of the drive gear. Another thought. Have you pulled the pump apart and checked the internal condition.? I'm wondering if something could have become stuck in the pump gears and taken the teeth off the gear.? Continuing on from that idea, what did you find in the magnetic screen for the pump suction.? I assume that you inspected it.
These guys are pretty good for both OEM and aftermarket parts. A number of HEF members speak highly of them. https://avspare.com/caterpillar/gear/7s8621/ - confirms the gear as having 59 teeth. You could also try Offroad Equipment in Alcoa TN. www.offroadeq.com/
Thanks very much! Yes..on that inside gear, we don't see any damage but it's hard to believe that is the case. Again, it looks okay. We pulled the bottom screen and we have some metal...but nothing large. It's almost like it was a constant wear down. I will look at the inside of the pump. I can turn it and it appears to have suction based on sound. About three years ago, the machine seemed to start sounding different...kinda of a growling. It's an open station so it was noticeable! We thought...torque converter. Then about 10 months ago...we were pushing some trees and stopped it. Fired the engine back up....no growling...didn't move. Hasn't moved since. Torque converter seems okay. Pulled this pump and found this issue. I'm like you...concerned of a secondary unseen issue. We spend about $2,000 on a $15,000 dozer and you still have a pasture shrine. I'll check these parts dealers out! Thanks for the help and your thoughts!
That gear has been running dry, it's supposed to be running in oil. The remnant teeth show a massive level of dry wear. What has happened to empty the TC compartment of oil? The compartment should retain a couple of quarts of oil at all times. Has the compartment plug been lost or damaged? My local dismantler, Swantrax, shows 1 x 7S8621 gear in stock, but I'd have to check with them Monday to ensure it actually still is in stock. The website of G.A. Ricambi, the Italian aftermarket part supplier, shows that they supply that gear. You will need to contact them to find out how and where you can acquire their gear. REPUESTOS PARA MAQUINARIA MOVIMIENTO DE TIERRAS – G.A. Ricambi www.garicambi.com
Following on from what Oz wrote above, at the very least you have a housing with a handful of broken teeth in it. I can’t see them getting down the drain line back to the transmission. So for that reason alone I would suggest more disassembly will be required to ensure the compartment is completely cleaned out. That disassembly would give you the opportunity to inspect the mating gear more closely.
That gear looks a right knacker job, on the D5's that part is flooding in oil you might want to take a big look inside, always a chance that the pump shaft is bent but would be lucky to get away so light, i tend to think the next bit it (The torque) has a cankered bearing, it will strip out easy enough.
Thanks very much for the information! I pulled up the Swantrax website. If you have a contact there, I very much appreciate the help or I can drop them an email. I'll check on the oil bath for that gear. It's an old dozer so it has it's share of leaks but nothing serious that I noticed. Thanks for the help!
I think you are right. The picture as to why is becoming clearer. If I can secure a gear, it might be wise to pull the transmission. I just can't get a bunch of money invested into something that leads to me selling a parts machine. Thanks for the info!
Thanks for the information! That growling before the gear quit making contact sure did sound like the TC to us. I'll add this to list of things to check. Thanks!
I think you're in for a fair amount of disassembly to get at the root cause. At the very least you need to take a look at the torque converter bearings as suggested above by TCT.
That cog can be repaired easy enough . The one it runs on probably damaged as well that would need to be done to . Crown wheel and pinons can be done with there curls and twists so this straight cut would be easy . Looks like you gears has been dry for years that will need to be sorted