1988 Harsco M936A2 Front axle Engagement

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Aloha Folks! We have a 1988 Harsco M936A2 Wrecker that was rebuilt at Red River in 2009. It only has 100 hours since the rebuild. We use it for skidding trees in the jungle. Great machine but we have one little issue. When we engage the front axle switch, the dashboard indicator light comes on but the front axle does not appear to be pulling. Given the many idiosyncrasies of these wreckers, we thought it better to check with fellow operators before tearing it apart. Is there some weird sequence that must be followed to get the front axle to engage?

While we are at it, perhaps folks could shed light on a couple other questions.

1. We "heard" that the automatic transmission was originally filled with engine oil but that the Marines later switched to ATF, because they were burning transmissions. The fluid in our transmission looks and smells like engine oil. What is it most likely to be? I called Red River but they could not tell me if they switched fluids during the rebuild.

2. When we check the transmission dipstick, on level ground with the trans running in neutral and warm, sometimes it show nearly empty and other times (exact same conditions) it appears overfull. WTF?

3. Are there no differential locks or limited slip on the rear drive axles?

4. What are the possible consequences of reversing in low range? There are multiple warning labels in the cab, warning not to do so.

5. What is the base chemistry of the chassis grease that would have been used at Red River?

Thanks much folks!
 

simp5782

Feo, Fuerte y Formal
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Standard gaa grease. You can use synthetic grease if you want. Reverse in low range over torques the bull gear and can crack the case in half. Plenty of threads on that.

Both rear axles pull together. no power divider or limited slip. You can get it with a civilian swap.

Fluid level can vary high or low. Just nothing drastically overfilled
 

74M35A2

Well-known member
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1. It is likely 30wt engine oil, as originally applied. Works fine, as does ATF fluid. ATF is red, as you would expect.
2-5 answered above.
 

Stewardship

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Turns out there was nothing wrong with the front axle engagement. Just takes a while for sufficient pneumatic pressure to build in the circuit. Sticky old mechanisms require a little extra persuasion. Patience cures all.
 

simp5782

Feo, Fuerte y Formal
Supporting Vendor
9,223
2,025
113
Location
Memphis, TN
Turns out there was nothing wrong with the front axle engagement. Just takes a while for sufficient pneumatic pressure to build in the circuit. Sticky old mechanisms require a little extra persuasion. Patience cures all.
Pressure protection valve. Easily replaceable. Does not open until 60psi
 
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