Broken HST/ No Reverse= HUGE $ to Fix!

[rbargeron]

....... I see there are 2 pairs of poppets/reliefs.....

Edit - actually 5 relief valves - two high-pressure check/relief valves for the forward & reverse circuits (identical). Three low-pressure ones protect the charge pump, HST filter, and HST housing. The shims on the filter relief are so it's a bit higher than the charge pump relief.

 

[Coyote machine]

Well it's official - I'm a third-worlder. I both fix stuff and the other night I made a part for the toaster. I just can't help myself. BTW, the Accord's sheet metal is restored, ready for paint (to be done by a pro)

I'm guilty as well- as a kid I took apart everything I could get my hands on. Some years later- now, I still take everything apart and most stuff eventually goes together. I'm currently working on an old David Bogen 1950ish monaural record player with a 10 amp tube driven amplifier and 10-12" monaural speaker! I've got sound but the tone arm only tracks part of the way across the record...
Nothing wrong with fixing stuff but our mostly throw away society doesn't really reward the efforts nor does it see a real value to the need, with certain exceptions....
Keep on chooglin'

 

[rbargeron]

........I'm currently working on an old David Bogen 1950ish monaural record player with a 10 amp tube driven amplifier and 10-12" monaural speaker!........

My dad took us to Radio Shack in Boston the day Sputnik launched (10-4-57). We got a Bogen DB130 amp with Garrard Changer and EV 15" Speaker system. Got hooked on good sound - still listen to Klipschorns today (sorry - I'm drifting off topic - must be the white hair)

Hey Brian -
Thanks a lot for emailing the pages from your manual - nice color graphics (my manual's b&w). The system is almost the same except the L48 doesn't have cruise control. Looking forward to getting back into the HST diagnosis soon. Thanks again.

 

[rbargeron]

I still haven't really gotten back to the L48, but I mentioned earlier I'd taken off the HST pedal linkage neutral-holder damper. This one acts like it has some internal wear - it's notchy going past the center position. Also, when relaxed, it is not self-centering. It pushes out to fully extended. It would make sense that it should return to mid-travel from either the extended or retracted position. My WSM doesn't troubleshoot the damper - but it would seem this one favors forward over reverse. Not sure it pushes hard enough to affect whether the pedal linkage rests in neutral. Any thoughts? A new damper is a couple hundred - anybody ever have to replace one?

 

[kuboman]

Not sure the dampener has any effect on where the peddle comes to rest. It is to dampen the peddle from abrupt movements. There should be a centering spring somewhere and they can become weak or stiff and rusted.

 

[kuboman]

The dampener is the same one that is used on a multitude of machines. You can buy one from JD for a little over a $100.

 

[rbargeron]

The dampener is the same one that is used on a multitude of machines. You can buy one from JD for a little over a $100.

Yes the damper is common to other HST models. I bought one for when it goes back together. To update this repair story, the L48 has finally reached the top of the queue in my garage bay and there has been a bit of progress.

The original symptoms were that reverse had stopped working, and forward was normal. Another symptom I noticed later was the hst pedal did not return to neutral without help - it was sluggish. I've done some tests on the lift, wheels off the floor. With brakes off, running forward was normal in all 3 ranges and reverse was slow but the wheels did turn in all 3 ranges. With brakes on, pedal forward can overpower them, engine pulls hard in all ranges, but in reverse the wheels don't turn, and engine doesn't load either.

This tells me the hst servo piston is barely moving out of neutral toward reverse. Moving the piston is the job of the regulator, a flow-proportioning spool valve mounted on the side of the hst unit. After cleaning it up under there, and making a couple special tools for cramped access, I got the 4 screws out of the regulator and took it off for closer inspection. (did NOT split the tractor or take off the under-frame).

The regulator didn't move smoothly on the bench - hard to know how it's supposed to act, but it should be better than that. So despite the WSM saying not to take the regulator apart - I took it apart. It's a nice piece of hydraulic machinery, (lists around $2k) but the valve spool didn't slide well, tending to get stuck in one direction. By spraying brake cleaner in the passages and working it back and forth, the spool freed up and then slid out fine. I was working over a clean cloth to catch any debris - after cleaning out anything that would come, there were a few tiny bits of metal on teh cloth. The valve spool is not scratched, the bores look good, spring is fine, even the o-ring looked ok. It is back together with a new o-ring, and a new assembly gasket is a couple days away. Pretty sure I preserved the "factory adjustment" by marking it before taking it apart. It will be interesting to see what difference it makes when it's back on the tractor.

 

[brain55]

A good dealership or a good dealership mechanic would have suggested that this be the course of action before seemingly making replacing the hydrostat the only option. I think most of us with some mechanical ability had come to the conclusion that the problem was likely in the servo or regulator.

Brian

 

[dodge man]

I saw your post on the damper and thought I'd chime in. My Bx was getting sticky in the forward direction and did not want to return to nuetral. I just disconnected it and its much better than with it hooked up. The forward and reverse really isn't jerky with it off, at least its not any worse.

Good luck with your fix working. Sounds like you might get lucky with an easy fix.

 

[rbargeron]

On the L48 the pedal centers ok with the engine stopped, but not when running. Maybe it will be better with the regulator freed up. I think the damper is intended to lessen the shocks to the HST, not to the operator. Although it might be both - I remember some hydraulic shuttles on older models that could change direction quick enough for a face plant in the steering wheel.