JD 4630 Hydraulic Question

Kick · Aug 28, 2015

Hello Everyone! Just purchased my first tractor. It's a 1973 John Deere 4630, with a Synchro-Range transmission. I have worked on quite a few tractors over the years; but, this is the first one I've owned. I have found lots of valuable info, and very helpful people on this forum, so I decided to join.

My first question is...(and I'm sure I'll have more) This tractor has whats called a Hydraulic Thermostat Bypass Valve. It is up underneath the hydraulic oil cooler, and has a long hose running back to the transmission case where the sump screen is. I noticed it was only used on the early model tractors, and then eliminated. How important is this to have on the machine? All the hoses are in bad shape, and need replacing, not to mention, it adds excess clutter. Would it be safe to eliminate this from the cooler circuit completely? I haven't been able to find much info on it. I think it may have something to do with cold weather shifting difficulty??? If anyone has any ideas or info, I would greatly appreciate it! Thank You!!

Tx Jim · Aug 28, 2015

IIRC you can remove it with no adverse affects.

MSM · Aug 28, 2015

In theory it would reduce the amount of oil in the bell housing so shifting was easier. The excess cold oil would cause the permaclutch to drag and would result in gear grinding when trying to shift when the tractor/trans oil was cold. Once the oil warmed up,the tractor would shift properly. Like tx jim said it can be removed with no ill effects, just let the tractor warm up some in cold weather before tying to take off.

tim s · Aug 28, 2015

Take it off it means nothing...I put a lot of them on back in the 70's and have taken even more of them Off since...

Kick · Aug 29, 2015

Thank you all for your expert advice! I was hoping I could just remove this from the tractor. Less potential leaks and clutter! Always a good thing! Thanks Again!!

OldCrow51 · Aug 31, 2015

(quoted from post at 04:44:25 08/29/15) Take it off it means nothing...I put a lot of them on back in the 70's and have taken even more of them Off since...

Tim/All,

Did they do the bypass on 4230s as well? My brother in law bought a 4230 and I told him about cleaning the sump screen to which he called me back and described what seems to be the same thing this gentleman has ran into. I told him I didn't know exactly what it was for but I'd try to find out once I have looked at it for myself. I haven't looked it over but decided to ask since it sounds like the same thing.

Thanks,

OldCrow

Tx Jim · Aug 31, 2015

OldCrow51
You can also remove hyd by-pass on the 4230.

tim s · Aug 31, 2015

Yes they did it on all early 30's except for those with power shift..I have taken a lot of them off around here with no after problems,,but maybe in the "very" cold areas it could make the clutch act up..I think only on the ones before late 1974..

OldCrow51 · Aug 31, 2015

Tim/Jim,

Thanks for the replies. We'll end up taking it off this fall when he brings it to his shop to fix a couple other things.

OldCrow

JD 4630 Hydraulic Question

Kick

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Tx Jim

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MSM

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tim s

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Kick

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OldCrow51

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Tx Jim

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tim s

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OldCrow51

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