Hydro locked up

[Tgtack 779]

Have a 1276 and the sundstrand hydro rear differential locked up today. Pump is spinning from the drive belt, but rear axles will not move forward or reverse. If lift the rear up tires will rotate in opposite direction. Thoughts as to what might have gone south? Was creeping forward loading on trailer, belt jumped off drive pulley and pump pulley, and wouldn't move after putting belt back on.

[squonk 41,346]

My thoughts are: # 1 Why did the belt jump off? Was the belt that worn or did a pulley fail. Since you probably would have seen that issue my feeling is :

# 2 You trans plate on your frame is cracked causing movement when you were loading on the ramp. This caused the little ball pin whooby dooby on the control linkage to come out of the plastic cam plate messing up that orientation. Or the pin is out completely and the wheel movement is the caused by where ever the the arm on the trans is stuck at which in this case is slightly reverse.

Edited June 24, 2018 by squonk

[Tgtack 779]

1 hour ago, squonk said:

My thoughts are: # 1 Why did the belt jump off? Was the belt that worn or did a pulley fail. Since you probably would have seen that issue my feeling is :

# 2 You trans plate on your frame is cracked causing movement when you were loading on the ramp. This caused the little ball pin whooby dooby on the control linkage to come out of the plastic cam plate messing up that orientation. Or the pin is out completely and the wheel movement is the caused by where ever the the arm on the trans is stuck at which in this case is slightly reverse.

 

I have a little issue with the idler pulley/brake handle linkage where the arm connected to the diff is worn. If not pushed down fully (yes the 66 model was push down, not pull up), sometimes belt will jump off. Only happened 3 times in almost 2 years. The frame was replaced with a non cracked frame when I went through the unit, and frame has the factory stiffner plates on it, so no cracked frame. 

[Sarge 3,463]

The 1276 has a 2-pinion differential - might be the cross pin came out. Another thing to look at - if that engagement arm is worn for the parking brake make certain it's moving the park brake arm far enough to disengage it fully. I had that happen once on the 1277 with a badly worn arm - it had enough power left in the hydrogear to shear the pawl arm clean off. Had to split the trans, repair the park pawl and while I was at it made a new arm from scratch - sans the worn areas. It's easier to make a new one versus welding up the worn areas and re-profiling the arm.  I had some real issues with that trans drive belt - aftermarket ones wouldn't work and it either wanted to jump off the idler pulley or slip at the engine end, finally found a NOS belt hanging at a local dealer - haven't had a problem since, in fact, it broke the frame again instead, lol.

 

Another thing - the HA profile belt really matters here on that series machine and it's pulleys. I ran the regular A belts for quite a few years and they finally wore a bad groove in the stock engine pulley to where the belt would always slip when using full hydro power. Finally had to weld up the pulley and re-cut it on the lathe to the correct angle - that also fixed the issue. Two weeks later, I found a NOS pulley on the auction site - when I restore it that one will be used instead. The HA profile belts are almost non-existent now - check your engine pulley and see if it has a bad groove about 1/4" down from the outside edge.

 

Sarge

[Tgtack 779]

Okay so now I feel like an idiot. While trying to figure out how to get the thing off the trailer, I started playing with the brake lever thinking about the comments Sarge said. While rocking it, I noticed that it looked like the tires were moving. So I figured what the heck, let me open the diverter valve. Low and behold, it rolled. After I got it on flat ground I decided to check the fluid, and while I had added some at the show as it does have a leak, fluid just touched the bottom of the stick, added fluid to the full level, started it up, and it runs like a champ! So now I have to figure out how to replace the leaking seals, control valve and an axle seal.

[19richie66 17,522]

I’ll take feeling like and idiot and a cheap fix over being a genius and a complete overhaul any day. Glad you got it figured out. 👍

[Pullstart 63,097]

Sorry Tim I’m late to the show here, but I’m glad there wasn’t anything catastrophic in your outcome!

 

Kevin