International 656 No Reverse!

[Saintbacon]

Hi there - I've posted about this problem, but I've done a good bit of research/testing since then so I feel like I can ask the question in a more intelligent way.

This is an international 3600a (It uses the 656 Hydro transmission, which is where I suspect the problem actually is).

Basically, I can pull full load in forward, but cannot go into reverse. This is a foot-controlled tractor. When I press on the reverse pedal, the cam shaft only moves a tiny little bit and the machine stays put. I found that the shuttle valve had a missing snap ring so I ordered/replaced it. Unfortunately the problem still persists.

Stuff I've Tried:
I've tried adjusting the adjusting block on the pump servo a couple of times to no avail.
Checked the servo pressure and it seems to be pretty steady around 400psi.
Removed/Disassembled/reassembled the cam assembly inside the transmission block. Seems OK.
Checked relevant check valves. they seemed to be in excellent shape.



Things I don't think it is:
I do not think that the problem is a leak in the center section transmission, because if that was the case the servo piston would be able to fully engage. Currently the cam shaft/pistons do not seem to go into the full reverse position. (Correct me if I'm wrong)

I have a bunch of manuals available, which I can email to anybody who is willing to assist. Appreciate any advice!!

This post was edited by Saintbacon on 09/27/2021 at 12:22 pm.

 

[used red MN]

You should likely prepare to spend more money on the transmission to get it operational then you have invested in the whole machine. I will attach a link to the ..know all.. people for IH hydros. If you have searched the net about your problem they have probably came up in the results. I would call them for advice. For anyone else replying to this, the transmission in this tractor is apparently nearly the same as a 656 Hydro. In the 2nd link is an thread from Red Power possibly covering your issue.
Herrs Hydrostatic

Hydro help article

 

[Saintbacon]

Thanks Used Red - I reached out to Herrs just now. I'll see what they can do. I did peruse the Hydro help article too but I'm not sure it covered the same problem. Appreciate any other ideas folks have. I know Jim Naden replied to a few related things on this site and was hoping he might be able to weigh in.

 

[Janicholson]

There (IIRC from this site 12 years ago) are two control valves near each other one is reverse and the other forward. They are the same, and if interchanged and one is bad, the tractor will go backwards, but not forwards. (grain of salt on this, as I cant remember the model of Hydro. Jim

 

[Al Baker(pumpman)]

There are two check valves, both look just like a small pipe fitting. They are just below your left heal as you sit on the seat. There will be a short hydraulic hose with JIC fittings attached to them. If one of these check valves fail you will get this problem. They are no longer available through CNH. I had the same issue and had to get them from a salvage yard. How to test is turn the two hoses around. Now you will have reverse, but no forward. Good luck,, Al

 

[Saintbacon]

I do not believe the foot operated models have a drive control valve - at least as named.

I attached a few more pictures if anybody wants to review them for ideas.

Basically the pump servo doesn't seem to want to go down into reverse all the way.

Thanks if anybody else has ideas!

 

[Saintbacon]

Appreciate the advice Al! I'll give it a shot.

 

[Saintbacon]

So quick update. I did another adjustment on the adjusting block inside the transmission.
Now, when I press on the reverse pedal, the tractor lurches backwards just a little bit. It stops moving almost immediately, but every time I press on the pedal, it does this same lurch. It almost seems as though it's starting to engage, but then loses pressure somewhere. I did look at the external high pressure lines but did not see anything leaking.

Any thoughts? I'm thinking I'll take another look at the check/relief valves. My guess is that something is stuck somewhere.

Thanks!

 

[Saintbacon]

Another update -

Capped off both the high pressure forward and reverse lines in order to be sure the problem was inside or outside the transmission. Unfortunately the same exact issue is happening. I went through pretty much every post containing the phrase 656 and came across some old posts saying that the problem might possibly be the relief valves. I am going to be swapping out the forward/reverse relief valves, despite the manual saying that it one dies, it'll stop forward AND reverse movement.
Worth a shot.