Nige
Senior Member
Replacement pump time I think, or repair your existing pump. There appears to be a Reman offering Part Number 20R-6494 available. Price parts vs Reman maybe.?
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Cat 938G rough shifting transmission
- Thread starter Jonathan Wurz
- Start date
Jonathan Wurz
Well-Known Member
The price for reman is $1130 and the parts I've got now are $660 but there are only two bushings. I'm not sure if the other two are the same or if it's a different P/N that I can't find.
Jonathan Wurz
Well-Known Member
Nige
Senior Member
If you are looking at the 6Y-4614 Pump Gp there should be a total of 4 x 3T-2094 Bushing, 2 in each half of the case.
Two bushings are listed as being part of the 6Y-4615 Body, and the other two as part of the 6Y-4621 Cover.
What you have listed above is fine provide that the Body and Cover are both in good condition and with no wear or damage. Try pricing the pair of them, worst case scenario, and see where that leads. Remember that the Body and Cover already include the bushes you you won't have to price them twice.
Two bushings are listed as being part of the 6Y-4615 Body, and the other two as part of the 6Y-4621 Cover.
What you have listed above is fine provide that the Body and Cover are both in good condition and with no wear or damage. Try pricing the pair of them, worst case scenario, and see where that leads. Remember that the Body and Cover already include the bushes you you won't have to price them twice.
Jonathan Wurz
Well-Known Member
So now I can buy 1 for the price of 2
Jonathan Wurz
Well-Known Member
So these are the specs from my service manual, but I can't find anything for clearance between the gear teeth and the pump body. Is this something that never wears enough to check?
Nige
Senior Member
If either the gears or the pump body is worn it ought to be immediately obvious because the surfaces of both will resemble a ploughed field.
Question: If you decide to replace the 4 bearings are you sure that you have the necessary tooling to do the job.? If the new ones are not correctly installed you could be in for a seized pump rather rapidly.
Question: If you decide to replace the 4 bearings are you sure that you have the necessary tooling to do the job.? If the new ones are not correctly installed you could be in for a seized pump rather rapidly.
Jonathan Wurz
Well-Known Member
The pump body and the gears don't seem to have any wear that I can see without using a micrometer to check clearences.
I'm not sure which tools I would need to install the bushings. My plan was to turn an oversize shaft down to size with my lathe to fit in the bushing and leave a shoulder at the top. I can then use this tool to press the bushing in with a hydraulic press. I am sure I have the tools to measure how far I need to press them into the pump.
I might be missing something, but I can't see any other tools I would need to install them.
I'm not quite sure how to get the old ones out though.
I'm not sure which tools I would need to install the bushings. My plan was to turn an oversize shaft down to size with my lathe to fit in the bushing and leave a shoulder at the top. I can then use this tool to press the bushing in with a hydraulic press. I am sure I have the tools to measure how far I need to press them into the pump.
I might be missing something, but I can't see any other tools I would need to install them.
I'm not quite sure how to get the old ones out though.
Nige
Senior Member
TBH I'd just throw a Reman pump into it and have done with it.
Jonathan Wurz
Well-Known Member
Might happen eventually but right now I've got the bushings out and I'm waiting for new ones. I can't see any damage that I could point to when asking for a new pump. Thanks for the help, I'll keep you posted.
CrossDrilledPiston
Member
Damn I'm clutching my pearls reading this thread. Gripping stuff. Also maybe because we just got a it98g with the same problems, and I am so damn grateful that you two already did the teeth pulling on this. Can't wait to pull the cab off tomorrow.
Nige
Senior Member
Make sure to post what you find including photos.
Jonathan Wurz
Well-Known Member
I've had the loader running for the past 4 days now, but I didn't want to post anything before running it for a couple of hours. THE ROUGH SHIFTING IS FIXED! I believe the differential valve was what fixed the speed changes.
The aerated oil is still aerated, with one change. Before, after running it hard for 15 min I had 1.5 inches of oil in the sight glass and 2-3 inches of foam on top of that.
Now there is no foam. I don't know what changed but I'm ready to except this and move on.
Thank you
"pulling it's teeth" with me.
The aerated oil is still aerated, with one change. Before, after running it hard for 15 min I had 1.5 inches of oil in the sight glass and 2-3 inches of foam on top of that.
Now there is no foam. I don't know what changed but I'm ready to except this and move on.
Thank you
"pulling it's teeth" with me.
Nige
Senior Member
With what you found in the differential valve it is apparent that the damaged one was was failing to prevent P1 pressure spikes immediately after a speed shift and causing rough shifting.
Jonathan Wurz
Well-Known Member
I'm Baaaaaaaack!
So I've got a long winded story today. Last thing I did was replace the trans pump bushings. I guess I shouldn't have done that, because after starting the tranny pump screamed and then stalled the engine.
I didn't realize at the time what actually happened, although it should have been obvious. I guess I didn't want to believe it. Well the pump unseized when I started it back up, but it was still having issues. Every day the oil would drain to the bottom and it would take 2 min to get it's prime back next morning. I didn't notice this all winter because I let it warm up for 20 min in the morning. Well, summer came and I didn't always let it warm up for 2 min. This is when I noticed that it wouldn't shift into gear right away. Now were back to winter and I had time to replace the pump, which I did with a reman pump. When I got the pump I installed the drive shaft and turned it to make sure it was smooth. After putting it in I didn't want seize this one too so I ran the starter but didn't let the engine start. After three times the oil started dropping in the sight glass so I started the engine and let it run. Everything seemed normal except for a slight buzzing sound at med to hi RPM. After 50 hours the pump seized and the shaft driving it broke off.
I replaced this one and ran the engine a little with the new pump and the noise came back. From what I can tell, it seems like the sound starts up after the engine has been running for a few min. This is about the same amount of time it takes for the oil to become aerated.
I forgot to mention between now and last time I posted, I switched to different oil. It was before I removed the first pump and it didn't seem to have a problem with it. Viscosity brand SAE30 and supposedly meets Cat TO-4 specs. Do you guys think this would make a big difference? I will switch back and see what happens.
In the meantime I have a different question. The oil gets aerated when I start the engine, but if I heat the transmission oil up to 180*F, the bubbles go away. Is it possible for the oil to get aerated from being discharged into the transmission through the torque converter inlet relief valve at 200 PSI? The relief valve is supposed to limit the pressure to 130 +/- 10 P3 pressure is around 200 PSI when the oil is 70*F. Torque converter outlet pressure is 150 at 70*F. These pressures are all normal once the oil is at operating temperature.
There is something else I don't understand there are 2 possible torque converter cooler circuits.
126-9584 4YS1-UP
197-5842 4YS705-UP (This one has an oil cooler bypass valve.)
My loader is 4YS1211 and it has the 126-9584 cooler circuit. was the bypass valve an option from the 705 SN# up?
So I've got a long winded story today. Last thing I did was replace the trans pump bushings. I guess I shouldn't have done that, because after starting the tranny pump screamed and then stalled the engine.
I didn't realize at the time what actually happened, although it should have been obvious. I guess I didn't want to believe it. Well the pump unseized when I started it back up, but it was still having issues. Every day the oil would drain to the bottom and it would take 2 min to get it's prime back next morning. I didn't notice this all winter because I let it warm up for 20 min in the morning. Well, summer came and I didn't always let it warm up for 2 min. This is when I noticed that it wouldn't shift into gear right away. Now were back to winter and I had time to replace the pump, which I did with a reman pump. When I got the pump I installed the drive shaft and turned it to make sure it was smooth. After putting it in I didn't want seize this one too so I ran the starter but didn't let the engine start. After three times the oil started dropping in the sight glass so I started the engine and let it run. Everything seemed normal except for a slight buzzing sound at med to hi RPM. After 50 hours the pump seized and the shaft driving it broke off.
I replaced this one and ran the engine a little with the new pump and the noise came back. From what I can tell, it seems like the sound starts up after the engine has been running for a few min. This is about the same amount of time it takes for the oil to become aerated.
I forgot to mention between now and last time I posted, I switched to different oil. It was before I removed the first pump and it didn't seem to have a problem with it. Viscosity brand SAE30 and supposedly meets Cat TO-4 specs. Do you guys think this would make a big difference? I will switch back and see what happens.
In the meantime I have a different question. The oil gets aerated when I start the engine, but if I heat the transmission oil up to 180*F, the bubbles go away. Is it possible for the oil to get aerated from being discharged into the transmission through the torque converter inlet relief valve at 200 PSI? The relief valve is supposed to limit the pressure to 130 +/- 10 P3 pressure is around 200 PSI when the oil is 70*F. Torque converter outlet pressure is 150 at 70*F. These pressures are all normal once the oil is at operating temperature.
There is something else I don't understand there are 2 possible torque converter cooler circuits.
126-9584 4YS1-UP
197-5842 4YS705-UP (This one has an oil cooler bypass valve.)
My loader is 4YS1211 and it has the 126-9584 cooler circuit. was the bypass valve an option from the 705 SN# up?
HATCHEQUIP
Senior Member
Just wandering where did these pumps come from?
Jonathan Wurz
Well-Known Member
Cat dealer
Reman P# 20R-6494
Reman P# 20R-6494
HATCHEQUIP
Senior Member
Your either starving for oil or cavitating. If your sure your screens and filters are clean have you thought about running it way overfull just long enough to see if it got the level higher than the suction leak, or maybe what might be better is with it making the sound try adding oil and see if it quits and what that level is ,,just a thought
Jonathan Wurz
Well-Known Member
So you don't think its possible the oil would aerate if it sprays into the top of the transmission through a relief valve?
Nige
Senior Member
Have you been into the converter inlet relief valve and inspected the internals.?
The TC inlet pressure should not rise above 130psi, even with cold oil. The function of the IRV is to control that pressure.
According to the listing of the chassis arrangement whether 126-9584 or 197-5842 is installed on a particular machine is an either/or situation. The chassis arrgt does not quote a Serial Number break for the two groups.
However information from another source indicates that 197-5842 replaced 126-9584 from 29/SEP/2000, almost a year after your particular machine was built. Somewhere around S/N 4YS1757.
Either way I think it's a bit of a red herring because the only function of the valve is to bypass the powertrain oil cooler when the oil is cold.
