IH 3121 backhoe

Joe L · May 6, 2009

I have a 1971 IH 3444 with a 3121 backhoe. The backhoe swing has a lot of slop to it, I suspect the gears in the rack and pinion drive mechanism are worn. Is this reasonable to fix and are there parts available? Does anyone have experience with this?

Roy Ward · May 6, 2009

I had 2 of them. One is working very well. The other one your just about a month to late I haul it to the junk. I did keep all the cylinders and the control unit off of it. I have a complete parts and service manual for it. I have been able to get parts from case over the years. Most of the part numbers in my manuals are still good numbers. The manuals are 4 inches thick. I made a round bale hauler out of the 3444 that I took the 3121 off of. I overhauled both 3444 engines last winter. I also have a rebuildable head with valves for the BD154 engine.

JDemaris · May 6, 2009

The slop is usually from worn splines in that big cast yoke on top. Easy to change, but pretty hard to find a replacement. 3 1/4" OD shaft with 32 splines. IH part # 468389R11.

I just recently found a good one for my hoe, but that was a rare find. Some people just drill into the yoke and splined shaft and drive in pins to take up the slop.

Joe L · May 6, 2009

Thanks, I also noticed the slop between those two parts. I also noticed the shaft has dropped down a little bit, should a shim (load washer) be added to the bottom to bring that up a bit? I'll search for a new part. Do you know why the hydraulic line passes thru the center of that shaft?

Joe L · May 6, 2009

Thanks Roy, if you ever hear of another, I'd appreciate you keeping me in mind.

JDemaris · May 6, 2009

Isn't that just the swing-circuit oil return line? That shaft is the pinon gear that rides on a rack. One each end of that rack is a piston and cylinder cap. One cap for left, and one cap for right - and each cap has pressure oil coming into it. So the hose in the center is how it gets back out and back to the oil sump, I assume.

JLE · May 9, 2009

The small line a leak off line, lets oil that by passes in he cylinders to return to supply.
The cylinders are cam shaped to the main body, allow some ajustment for the rack and pinion. Dosen't take much, be sure and turn both cylinders the same way and same amount. Try one hole at a time. (which way?? I do'nt know)

ozone · May 16, 2009

I have a 70 or so 3444 with a 3141 hoe on the back. Lots of slop in my spline as well. Do not try to weld it, it just breaks. My next attempt at a fix is to drill three 3/8" holes around the perimeter and tap in 7/16 bolts to take up the slack.

IH 3121 backhoe

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