Old D7 not spinning the torque converter. Understanding the principle

[fastline]

I am trying to get some equipment moved for a friend. Fired up this old D7E and realized it would not go in gear (powershift). Just felt like a manual gearbox where the gears were not lined up. So I pulled some floor pan up and realized the TC, or rather the large U joint is not spinning. That may point to a problem! Obviously fluid needs to be in it to work, so I am guessing a transmission pump is potentially at issue?

Anyone have thoughts on this. Principles of how it all works? Learning what trans this machine has and how to service it would be super. Please don't tell me the trans needs to come out just for a pump issue?

 

[Nige]

Well you got the first bit right, it needs oil in it. Have you checked the level..?

 

[fastline]

Oh yes, oil level is over full. The TC doesn't even think about moving. I hear the trans oil pump is mounted at the lower right of the engine. Trying to think now of a way to either verify the pump is turning at all or there is a draw tube issue. Air leak? Draw tube fell off in trans? Can that happen? Maybe intake screen plugged? Thoughts?

 

[Nige]

Unfortunately I don't think I can be a lot of help because there is no online info available for the D7E.
Someone like Old Magnet (haven't seen him on here for a while come to think of it) or O-I-H would probably be your best bet.

 

[DMiller]

With the machine OFF and in Neutral gate will that ujoint rotate by hand? Will it rotate with a SMALL crowbar, if not there is serious failure INSIDE the trans or TC. Just drag from any amount of fluid in the TC should cause it to rotate free in Neutral with engine running.

 

[Mark250]

check to see if the converter turns by hand. if it does check for transmission pump prime.
on top of the pump there is a small plug, take that out and crank the engine over.
it will make a mess if it is primed, if not try and get some oil into that fitting.
you can jury rig a hose to catch any oil as it is under pressure or place something over the top to stop it spraying
Mark

 

[fastline]

Good ideas. I understand the spec to be 300-330psi off that pump port? I do not recall seeing trans pressure on the gauge when we were idling it. What would make the pump lose prime? My other one sat for years and just picked up and went with no issue!

maybe a weak pump and unable to prime itself? Or is there possibly a check valve that needs work?

 

[Mark250]

generally the suction hoses and seals go hard and don't seal properly and suck air.
A worn out pump will be very similar. The pump is easy easy to get too and easy to pull apart for inspection
Mark

 

[fastline]

Not certain on all the details just yet but this dozer may possibly only have less than 1000 hours on it! The meter has obviously stopped working but there are some other clues. I am not sure how long those pumps would last but unless the pump ingested something, I would be inclined to exclude the pump itself as being just worn out. Sounds like I need to study this section a bit. Hopefully CAT comes through with a service manual for me. Need something desperately on it.

One of my concerns is the pickup tube inside the trans has been damaged, fallen off, or otherwise sucking air. I have no idea if that tube is accessible at all.

If I knew what model of transmission this was, at least I could research the trans to try to learn more about the pickup tube.

Unless there is some sort of check valve, it would seem certain that the suction and pressure lines from pump to trans would drain down after shutting down the engine. I know on my own 7, the trans pressure builds over a period of about 10sec when first started. I guess I would expect a pretty large air leak to nullify all fluid pressure.

 

[Nige]

Have you tried registering on the ACMOC forum and ask about manuals..?
www.acmoc.org/

 

[fastline]

I am registered over there. Have not asked about manuals I don't believe though.

 

[edgephoto]

A quick search yielded these results......
https://www.agkits.com/caterpillar-d7e-crawler-service-manual-htct-sd747a1.aspx
https://www.amazon.com/Caterpillar-Crawler-Service-Manual-CT-S-D747A3396/dp/B01CGM95U0
https://www.yesterdaystractors.com/CTSD747A3396_3469.htm
http://www.ssbtractor.com/tractor_manual_display.cgi?m=Caterpillar&o=D7E Crawler

 

[dozr]

have been on one but can not remind my self does it have two speed like old 977h. if so it could be out of gear.

 

[fastline]

3spd, 3fw, 3rev, powershift trans.

 

[kshansen]

have been on one but can not remind my self does it have two speed like old 977h. if so it could be out of gear.

Even if it was out of gear the driveshaft between the converter and the transmission should take off spinning once a little oil gets to the converter.

 

[fastline]

I finally got all the books for the machine. Though they are loaded with helpful info, nothing shows the pickup tube or assembly that collects oil from the trans or clutch sumps.

Here is what is bugging me. The shifter will not even move. running or not. The shifter does not manually operate any gears, it is simply connected to a hydraulic spool valve. It should move! I know another one that will move without issue or fuss. This makes me wonder about foreign objects being stuck in the spool, however, the shifting runs off the gear pump, that that fluid is protected by a magnetic pickup strainer and a downstream media filter.

Just odd and not sure where to start.

 

[dozr]

i would remove shift lever from tran ,then see if lever would move then shift tran with bar or pilers what ever worked sounds like frose up lever to me. sat to long from last job, or used to much when new,mite as well have a little fun with it.

 

[fastline]

Just got some history on this dozer and seems it recently had a rebuilt converter and trans pump installed because the last converter was overheating and vanes were damaged. Also had the main ring gear bearings go out and they had to pull the steering clutches and install those bearings. Then it would not steer right and was discovered that trans pressure was on target but when activating a steering clutch, it dropped to 30psi.

Metal was found in the oil...........................................................................I want to puke...This machine just became one of those nightmare machines. Once fines get worked into the system, it will probably eat expensive parts for the rest of its days.

At worst, it needs clutches, trans rebuild, converter, trans pump, and every spool cleaned and checked.

I have no idea if the trans pump is good or not, but may not surprise me to see it broke to pieces. What is very sad and baffling is the machine has no real hours on it! But I think the guy that bought it put it in his fleet like any modern machine and probably had an 18yo kid on it that cannot be bothered to watch gauges. It is just a best guess how the carnage started, and also a best guess how bad it really is. This is where I get extremely frustrated with CAT in why they won't segregate systems. The oil in this situation runs through enough components to nearly total it when brand new, let alone today.

 

[56wrench]

did you pull the trans and steering clutch filters? that could help you narrow the problem down

 

[fastline]

Are you grouping those together? like trans/clutch filters? Because unless you know something I don't the clutches don't have their own filter. However, the pressure side filter from the pump does have 2 filter cartridges in it. It's possible there are two circuits there.

There is also a suction side "magnetic screen filter", whatever that means.

I did not make it over to look at it more. I needed to think about it for a while.

I think looking at the filters is probably the best route for now, and probably pull the front off the trans pump so I can inspect the gears. That will help tell me how much grinding it did.

Indication from the service reports is "large chuck of metal were found in the magnetic screen". The oil analysis also showed higher amounts of metals. Love to see that report.

It is not normal to see the bearings on a ring gear fail. That should have been a clue to dig deeper.