62 power steering gearbox question

[Wile E Coyote]

I've been perusing the several write-ups on box rebuilds, but still have questions.

I'm blaming my death-wobble on the 0.040" of backlash in my sector shaft (measured at the end of the pitman arm where the relay rod connects,) There is zero axial play in the sector shaft. Being hesitant to trash the box, I haven't been able to take up any backlash at all with greater than one full-turn of the preload screw on top of the box.

The 35-45 mph death wobble is pretty bad and is made worse by virtually dead front shocks (that will also be fixed with new upper mounts for new Billies) so this needs fixed. However, this is my DD, so I'm trying to avoid the long-ish downtime of sending it out for rebuild. Not a drop of leaking, no groaning, no 'dead spots' just very loose sector shaft. The steering wheel travel is in spec, BTW.

On to the questions: Is it reasonable to expect I can get the sector shaft backlash to zero and keep the preload on the worm gear acceptable? The mesh of the worm and sector shafts IS the backlash I'm measuring, right? With currently zero axial play in the sector shaft, just how much affect does that adjuster screw have?

 

[cruisermatt]

0.040" at the end of the pitman arm is very little at the shaft itself (basic geometry). Have you looked up the tolerances in the FSM?

 

[Wile E Coyote]

Thanks for the input.
I agree that '40 thou' at the end of the pitman arm must be minuscule at the gears themselves, and I checked and rechecked with the dial indicator and mag base. The amount of visual and audible feedback I get when moving the pitman arm by hand with the relay rod disconnected (clearly moves and loudly clunks) also doesn't match the number I get, so perhaps I'm overlooking some slop in my indicator base setup.
Anyway, my re-read of the fsm this morning is that the overall backlash should be zero, but I also now see where I can control the preload of the worm gear and the sector shaft independently.

I'm going to order a rebuild kit and go for it.

Is the 80 series box a direct swap for my late 60 series box? What about 2nd gen Mini truck boxes? Anyone have a rebuildable direct-swap box I can tear into to reduce my downtime?

 

[SteveH]

Steering box play would be on my list of death-wobble causes, but not near the top. Caster angle would be the first thing I'd check.

At the risk of offending, I wonder if you're overthinking this box play issue. Adjusting the steering box is typically done just to eliminate play in the steering wheel, and is always a compromise between eliminating ALL the play and not having the steering wheel 'stick' when you go around a corner, due to the adjustment being too tight. I adjust my boxes in the sweet spot to where the steering wheel won't stick when you go around corners, and to where they have as little play as possible in the center. (Steering boxes wear in the center more than at the turning extremes, which is why there is no perfect way to adjust at used/worn steering box). When I am 'done' adjusting the box, it's a lot better, but not like a new truck. You're never going to get rack-and-pinion feel out of a recirculating ball steering box, so quit while you're ahead, and find the root cause of your death wobble, which likely isn't the box.

If you rebuild the box, please update this thread with your findings. I have always just put up with the wear in my Toyota steering boxes, but it would be nice to hear of a rebuild that creating a dramatically better driving sensation.

 

[3_puppies]

assuming you went thru all the easy stuff first, spring bushings, u-bolts, tierod ends and drag link ends, tires and wheels true and balanced.

 

[Wile E Coyote]

I agree that the pitman arm 'slop' isn't on the top of the list, which is why it took me a long time to work my way down to it. It's basically last on my list, (along with the dead shocks I mentioned).
Wheel bearings are tight, knuckle bearings are tight, rod ends were tight, but I replaced them along with the new tie rod last month since it's threads were very buggered. Steering stabilizer is 2 years old and has no dead spots when cycled by hand. Driveway alignment at 1/8" toe-in measured at the outer circumference of the tire ( Since the new tie rod adjusts so damn smoothly now, I experimented by upping toe-in to 3/16" with no change) Drag link preloads are out one full turn, caster is 2.5 deg both sides ( purposely a little higher to accommodate a planned taller tire) Tires rotated F/R and L/R more than once since the DW started. Spring bushings are rubber up front and poly in the through-frame shackle reversal I did, and pass my 3 foot pry bar test. Springs are rear Chevy Blazer springs with one extra leaf each, all mounted with modified u-bolt flip plates from Ruff Stuff.
Lots of home brew non-stock stuff going on under there, but I've come to the steering box after ruling out everything but the shocks.

 

[Output Shaft]

This article has everything you might want to know about death wobble.

Do The Harlem Shake! - Death Wobble - Jp Magazine

 

[lovetoski]

The 80 box is a direct swap for the late 60 box. Not sure that's your problem, but you asked the question.

 

[Wile E Coyote]

Setting preload

• Wile E Coyote
• Mar 13, 2017

Regular 6-sided socket fit over the splined worm shaft enough to set the very light preload with...

Power steering box

• Wile E Coyote
• Mar 13, 2017

Rebuilt the steering gear box to tighten up the slop.

Over the weekend, I dove into opening the box to tighten it up.
I found that a 6-sided socket fit juust snugly enough over the splined shaft to use my in-lb torque wrench to set the worm gear preload. The overall preload was then set, but like I was warned, I couldn't get the backlash to zero through the entire range of the sector shaft. Zero backlash at either end of the sweep and the sector shaft bound up as it neared center, so I found my compromise point I was comfortable with.
Contrary to the feedback received here, it totally eliminated my death wobble.

The steering is still not where I'd like, however. I still have to re-center my steering wheel & I only had time to cut off one stock upper shock mount & install the modified ford F250 upper mount for the new 10 in. Billies i'd already ordered. (Again, this is my DD, but luckily my drive is very short and on surface streets) So, one dead shock and stock mount remains...which means it reacts poorly to road bumps, but solidified my thought that the shocks were dead...very dead.