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Durango gear box backlash questions


NAXJA Forum User
Vancouver Island
I have a '98 Dodge Durango gear box in my '99 Cherokee. I replaced all the seals recently and started playing with the backlash ("steering wheel play") with the box installed in the vehicle. I noticed that adjusting the backlash allen bolt doesn't seem to do much of anything. The allen bolt can be turned about 1 full revolution only before it gets too hard to turn. In other words, if the allen bolt is in the middle of this turn radius, it can go a half revolution in either direction before it is too stiff to turn with an allen key. On my PSC SG-621M gear box, that allen bolt can turn about 3 full revolutions before being too tight.

On all these saginaw type gear boxes, is it always that a clockwise turn of the allen bolt reduces backlash (less play) while a counter-clockwise turn increases it (more play)? Contrary to what most people do, I am actually trying to give more steering wheel more play, not less. With the exception of the fringe edges of that full revolution of the allen bolt, I'm not really noticing any play added to the steering when driving the vehicle. Is this a common occurrence?

Is the ideal positioning of the allen bolt right in the centre of that full revolution? On my PSC box, with it on the bench, the centre position has a bit of a "knot" when the pinion is at centre revolution when the allen bolt is in the middle of its turning radius. To get rid of that "knot", the allen bolt needs to be turned about a half revolution counter-clockwise from centre. Is there a general rule of thumb for finding the factory centre without using a backlash meter (I don't have one)? What is the factory backlash spec for a '98 Durango gear box and a PSC SG-621M (now called the SG061R)?

I wish I had played with this with it was out of the vehicle, but it is too late for that. Based on the position required to get the "knot" out of the PSC box, I've adjusted the Durango box allen bolt to be a quarter turn counter clock-wise off of the centre of range of motion. If you picture a clock, with 12:00 being tight, 6:00 being the loosest, and 11:59 being tight again, I've positioned the allen bolt at 3:00. And anywhere from 1:00 to 10:00, I don't really notice any change in the steering wheel play. It starts to get tight again around 12:00, either direction. What's to be made of this?
LOL! I think I solved the mystery of only having one full revolution of the allen set bolt - the Ironman4x4fab steering box brace, which also grabs the pitman shaft, isn't allowing for any downward motion. So that full revolution of allen bolt movement movement, which perhaps translates to no more than 1/8" of an inch of lateral motion in the pitman shaft, is due to stretching of the Ironman's pitman shaft bearing and set screws. I'm glad I didn't drive it more than a day like this. For anyone with an Ironman4x4fab steering box brace who wants to adjust gear box play, be sure to loosen the Ironman's 2 set screws on the pitman shaft first.

My original question of how to find the factory centre backlash without a backlash meter still remains though. Although I had marked the position of the gear box's allen set bolt, that position is a position for which I had, years ago, tightened the play. Now that my I have replaced all the joints in my steering, I want to add back some play and it would be nice to find the original centre again without removing the box, or removing the Ironman4x4fab steering box brace and swaybar.
Pardon me, I wrote one of those incorrectly. The 45-deg torque (overcenter torque) should be 4-8 in-lbs greater than the 90-180-deg torque. But I am a little confused by the seemingly inconsistent use of nomenclature. Specifications mention the "Worm Shaft Bearing Preload" to be 4-10 in-lbs and the "Pitman Shaft Overcenter Drag" to be 4-5 in-lbs plus the "Worm Shaft Preload". I did not see a procedure to measure the "Worm Shaft Preload"; only to tighten up the adjuster (one with the two holes needing a spanner) fully then backoff 5.08 mm.

Is it that the 45-deg overcentre torque should be (4-5) in-lbs plus (4-10 in-lbs), that is, 8-15 in-lbs?
Having rebuilt, ported, and sold over a hundred boxes the method of setting the lash by feel. By design, the lash will be the tightest right in the middle of the range of motion. While I have done it in vehicle, it is best done on a bench, in a vice. Start by rotating the input shaft lock to lock and count the turns. Divide the range in half and rotate the input to that point. Put a wrench on the input shaft and rotate back and forth over this point. Slowly tighten the adjuster until you just start to feel the force increase as it travels over the center point. I like to start by adjusting it way too tight to get things settled and then back off to where you don't feel any increase as you rotate the shaft back and forth and then slowly tighten until you just start to feel the increase in force and then back off the adjuster screw 20 degrees and lock it down.

Double check by turning the input shaft lock to lock a few times.

You can do it in the vehicle but you need to uncouple both the input and output shafts before adjusting.
Thanks. This qualitative method is a method I also came to for the PSC box I have on the bench that I was playing with. Unfortunately, my Durango box is already installed.

You say it can be done on vehicle if remove the pitman arm and steering column. But will the box being full of fluid make finding that tight "knot" in the overcentre position difficult? Or does the box also need to be drained when on vehicle?
Well this is really frustrating. Yesterday, I adjusted the allen screw and the steering drove like a new car after numerous trial and errors. I was satisfied.

This morning, drove the car and it was stiff as a board. After 10 minutes of driving, it eased up some, but not quite like a new car again. What is going on here? Does this suggest that there is air stuck in the gear box? As the car warms up, air trapped in the gear box is heated and thus expands. The expanded air puts more pressure on the fluid making turning easy again. I'm just speculating.

After I rebuilt the Durango box, I filled it up as much as I could with the pitman shaft off. Installed the box. Filled the reservoir. With the tyres off the ground and engine off, turned steering wheel back and forth slowly and filled the reservoir as the box filled with fluid. Once I didn't see the reservoir level dropping, I then turned the car on for a split second, then off. Checked level. Filled. Did this repeatedly. Then left the car on and turned a bit, filled, turned more, filled, etc. until the level stopped dropping. Did I do something wrong to get air in the box?

Any advice appreciated. I'm getting ready to throw this gear box over the fence.