Hydrostatic transmission troubleshooting

[bsengrx2]

Hello all,

While no longer a complete newbie to these tractors, I still have many questions. With the rototiller and snow thrower, the transmision on this old girl has been taking a lot of abuse.

The tractor is an Allis Chalmers 716H from 1978 model # 1690211. According to this link:http://simpletractors.com/Club2/topic.asp?TOPIC_ID=124539 the transmission part number is 1650301.

One symptom is that when starting cold, forward or reverse, will not move for a bit and then builds up to whatever speed set. Another is that when backing off on the speed, it seems to be slow to respond. Rather than come to a stop it rolls a bit.

The filter is a few years old. I have been through the process of bleeding and haven'tseen any benefit. To tell the truth I feel like I'm going through the motions and am not clear on what is behind the steps.

Looking forward to hearing back.

Tom

[Marty-MN]

I would put a pressure gauge on the transmission and see what the pressure is when starting cold and check again after it has been run for a while

[Brettw]

What are you using for fluid, and are you sure you are full?

[B-16_IC]

If it's also slow to respond slowing down check the nylon roller in the linkage, it's right in the middle above the transmission when you tilt the seat pan back. If it is worn or not rolling smooth it will cause sluggish response that sometimes gets better after warming up.

[bsengrx2]

Hello again all,

I checked the fluid level and it appears fine. As said, I am not that confident in bleeding the system because the level never seems to change. Well, rather than mess around with the hydraulics I thought I would take a look at that roller B-16_IC mentioned. The linkages of the control mechanism leave a little to be desired but what is expected after almost 40 years. I have a video posted here:

and i think the control lever isn't moving the lever going into the transmission. The roller is in the mail and we will see where that leads. I'll keep you posted.

Tom

[Kenzen]

With the engine off, check that moving the control lever actually moves the linkage full-range. There's a spring damper (if it's like my 917H) that will not fully decompress if the linkage is binding due to lack of lubrication. Also, I had a loose nut connecting to the control lever, causing play that made the tractor slow/sluggish. I took the lever out and cleaned/greased the spring washers, reassembled, and it's very responsive now.

Also, the check valves may be worn to the point where they leak by, causing loss of drive pressure.

[bsengrx2]

It clearly isn't moving over the whole range. When the roller comes I'll go through it, start with the simple.

[bsengrx2]

Well the bushing showed up and the linkages are all much tighter. Using the reccommended fluid, it's level is full. Went through the bleeding proceedure without any noticble change in the fluid level. I assume this means there wasn't any air in the system. The problems have gotten better and worse. The gradual change in speed to the speed setting has gone. The position of the transmission goes right were it should. So the bushing was definitely needed. Thw new problem is that when parked on a hill and in neutral, it rolls downhill. Anyone have a reccomendation, rebuild manual, or advice?

Tom

[Kenzen]

Does it roll with the engine on or off? You may have insufficient charge pressure if it happens during running. Running or not, your check valves may be leaking by. (These are the two things with the nipples under the seat that you push down to allow the tractor to be pushed around when not running.) If they are still avail new, they are expensive. There is/was a guy on the web and ebay that offered a service to rebuild the ones you have, as well as offered a kit to do it yourself. You need to be able to weld to repair these. The guy doing it is/was a Cub Cadet expert, but its the same sundstrand hydro unit.

[goatfarmer]

quote:Originally posted by bsengrx2

Thw new problem is that when parked on a hill and in neutral, it rolls downhill. Anyone have a recommendation, rebuild manual, or advice?Tom

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id="quote">

id="quote">Advice? don't park on a hill in neutral. Gee, sometimes the simplest things.....If it helps, my 712H would roll a bit in neutral, depending on the grade it was parked on. It may be inherent to the transmission.

[bsengrx2]

Well I only identified it when off, if it ever stops raining I will check with it running. How do I find out the series of the transmission based on the part number 1650301? I'm an engineer and paperwork makes me feel better.

Tom

[Brettw]

They will all roll when not running without the park brake on. That is completely normal. For the most part, the Sundstrand pump in your tractor is pretty bullet proof. Although Im sure they do, I have yet to see one fail, myself. Rear ends, differentials, linkages, belts and idlers, all the other stuff that works together to make up the transmission as a whole I have seen fail, but never the pump. JMHO

[Simplicity7013H]

My 7117 does the same thing. It rolls when the engine is off. Works great when its running though.

[qcflyer]

I'm new to the lawn tractor world having recently acquired a Simplicity 4212 Hydrostatic unit. The other day I was towing with it and over about 50 yards the tractor gradually slowed to a stop. I replaced the drive belt but had the same problem. Turns out the transmission is slipping. The fluid reservoir is full. It runs fine without a load. The manual doesn't address this situation. I searched the forum for hydrostatic transmission slipping and came up empty. I am looking for guidance on the problem and how to fix it.

Thanks.

[Brettw]

gcflyer

If it still pulls when under a load, you might get some use out of it, but basically, the trans is kaput. And I don't believe it is servicable. Even if it were, the cost would be prohibitive for the value of the tractor.

[maxwood]

Hello, the proper filter is important I went to auto zone to get a filter

As Napa was closed ? I purchased a stp brand filter that was supposed to be an match ,but had nothing but sluggish erratic operation.

Thanks, Ken in Mi

[bsengrx2]

After listening to all the advice, doing and checking what fit in my limited time, I couldn't find anything wrong. The best solution for me was to leave well enough alone and tighten my parking brake. Thank you for the reassurance that this is just a sign of age rather than something to jump on immediately.

Tom