HD4 Dozer - Torque Converter Hydraulics problem? Won't move

mikeroche56 · Jan 25, 2016

Hi, I inherited a HD4, 1968 (S/N 3552). After sitting for a couple years, we had a couple coolant hoses to replace and the starter was toast. Got it running and drove it some, engine runs great. The power cut out to the tracks a couple times intermittently. I was able to operate it for about 15 min. to get down to the road to load it on a trailer without issue. After trailering it and offloading at my place it wouldn't move, no fwd or reverse. I drained the converter fluid (both front and rear chambers). Added 4 gal. new ATF and ran to fill front chamber, but it wouldn't take the remaining 2 gal. Cleaned suction screen, replaced filter behind grill. I screwed pressure gages into the two test ports in the shuttle clutch, reading no pressure on either port. The converter pump is pumping somewhat, tried cracking a fitting when running and got some atf coming out, but not as high as I would expect. I'm thinking I need to replace the converter pump. Any other ideas of what to check before I spend the money ?

Sorry for the long post, and thanks in advance for any help!! Mike

Nordic · Jan 25, 2016

Sure sounds like the converter pump to me. Not so much that the pump itself is gone but the converter neck meant to propel the pump is likely not engaging. It's possible that the flex plate that the converter is bolted to is cracked...which if it is the converter is able to start wobbling and given a bit of time the notches that drive the pump get rounded corners and finally there is not enough grip to pull the pump under pressure.

mikeroche56 · Jan 25, 2016

Thanks for the reply, Nordic! So it sounds like you are thinking the the torque converter itself may be bad. I was thinking this was a possibility, but since I dont see pressure at the shuttle clutch valve in either test port (clutch nor converter) was thinking there might be a chance it could be something else. The shop manual describes a pump flow meter to test flow rate coming out of the pump at a given pressure (the gear hyd pump that operates the.clutch/ torque converter circuit) but isnt something I have access to.

jim_uny · Jan 26, 2016

also try nnalert website under construction. there are some good mechanics there. also get a service manual.

farmallsforever · Jan 26, 2016

Back in the 80's, I worksd on a HD4 that would not move. It ended up that the blades had broken off inside the torque converter. I replaced the T.C. and it went back to work.

mikeroche56 · Jan 26, 2016

Thanks for the reply, Farmallsforever, I am hoping that is not the issue, gotta believe that is a hugely expensive part (if I can still get one). Do you happen to remember how you were able to definitively diagnose that it was the TC? Thanks, Mike,

Nordic · Jan 26, 2016

(quoted from post at 17:10:07 01/25/16) Thanks for the reply, Nordic! So it sounds like you are thinking the the torque converter itself may be bad. I was thinking this was a possibility, but since I dont see pressure at the shuttle clutch valve in either test port (clutch nor converter) was thinking there might be a chance it could be something else. The shop manual describes a pump flow meter to test flow rate coming out of the pump at a given pressure (the gear hyd pump that operates the.clutch/ torque converter circuit) but isnt something I have access to.

The possibility that I discussed yesterday wouldn't mean that the torque converter is bad inside - only that the protruding part of the converter neck has the driving notches damaged. Mine wasn't an HD4 but a similar set up. My Dad is great with welding and machining so he built up the converter neck with weld and re-machined it to spec. In my case the flex plate was damaged but with a new flex plate and new seal at the front of the pump (using the same old pump) everything went back together and worked 100%. The fact that your machine worked a bit intermittently at the end makes me think the drive to the pump was going...going and finally just went. If you pull the components apart you will soon see. If you don't see anything visibly wrong you know it's internal somewhere.

pinball · Jan 26, 2016

If you go to the allis chalmers forum and ask that questions theres 3/4 guys on there that really know there H4 dozers.

mikeroche56 · Jan 28, 2016

Thanks jim_uny, good suggestion! I've got it posted on nnalert also.

randaleky · Jan 28, 2016

do not forget the fact that it ran when you picked it up and unloaded. i think the main factor is that you drained the oil and now it won't move, but you could only get 1/2 the required oil back in torque housing. try to get near the book 33 quart and it should move.

mikeroche56 · Jan 29, 2016

Thanks randaleky, it makes sense, but still scratching my head as to why I couldn't get the oil to transfer to the forward case to accept the remaining oil... I reread the manual and it states to fill the rear case with 4 gal, then idle for a period to purge any air, and then up the rpms on it for a few minutes to transfer fluid to front so you have room for the remaining 2 gal. So hopefully this weekend trying running with the test port plug out of the shuttle clutch valve body to purge will be enough to get it pumping. Otherwise I think I might need a new pump... Open to other ideas to check for though

thanks again for all of the help!

mikeroche56 · Jan 29, 2016

The manual does mention that 9 qts stay in the torque converter and lines when you drain it so that is how you get to 33 qts by only adding 24. I think if I can get the remaining 8 qts in, I should be full.

Blackhole49 · Jan 30, 2016

If this isn't the Allis Chalmers forum' where is it?

Nordic · Jan 30, 2016

(quoted from post at 05:29:39 01/30/16) If this isn't the Allis Chalmers forum' where is it?

I think pinball was referring to the Allis Chalmers.com site

mikeroche56 · Jan 31, 2016

(reply to post at 12:07:50 01/30/16)

HD4 Dozer - Torque Converter Hydraulics problem? Won't move

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