Death wobble, have I tried everything

Post by **wesk** » Fri Apr 30, 2021 11:22 am

You may be near a solution. With as much grief as this problem has caused you it is worth a proper investigation/evaluation. I am a real pessimist when someone tells that whatever we were looking at "WAS COMPLETELY OVERAULED" ! I feel that is a very often abused phrase. Looks like a proper examination of the steering gear box is needed. Try using the two Ross Steering Gear manuals in our downloads list. Civyy & military.

4x4M38 · Post by **4x4M38** » Fri Apr 30, 2021 7:33 pm

He may have replaced the sector shaft but not the bushings. I have a ton of play in my sector shaft. At least a half inch. I’m sure the bushings are shot in mine.
There are two different diameter sector shafts as well..

JeepdaddyRC · Post by **JeepdaddyRC** » Sat May 01, 2021 7:59 am

I believe I have it narrowed down to the Ross steering box. You may recall the PO replaced the worm shaft, sector shaft and pitman arm.

With front wheels up and steering wheel solidly anchored, there is a full inch of play back and forth at the front tires and the steering wheel does not turn - but the steering wheel does rise and fall.

Does this mean the bearing preload was not set correctly (too many shims per TM9-8015-2, par 205)?

Post by **wesk** » Sat May 01, 2021 10:29 am

Before you become mired in the vehicle's operator manual do try to review the Ross Steering Gear Manuals I have loaded in our "Downloads" section. Both the original civvy Ross manual is there and the very detailed Army TM on the Ross Steering.

http://www.willysmjeeps.com/v2/modules. ... it&lid=136

http://www.willysmjeeps.com/v2/modules. ... it&lid=183

JeepdaddyRC · Post by **JeepdaddyRC** » Sat May 01, 2021 3:42 pm

Have been studying Ross manuals. Thanks Wes!
This is becoming even more interesting.
I understand that point I feel slight drag turning the steering wheel should be the midpoint, because the grooves in the Ross box are cut narrower and shallower in the straight ahead position.
However, when I feel the slight drag at steering wheel the tires are NOT pointed straight ahead (about 10 degrees to the left).
There is less than an inch of rotational "play" at the steering wheel "when at position of slight drag". This increases to 3 inches of play when the wheel is turned farther.
Could the PO install the pitman shaft incorrectly when the pitman shaft and worm drive were replaced?
Is that even possible?
If so, is it correctable with Ross box in the vehicle?

jtpasto · Post by **jtpasto** » Sat May 01, 2021 3:47 pm

Have you verified you do not have a belt separation in a tire or tires. They can cause a loping and feel like a death wobble.

RonD2 · Post by **RonD2** » Sat May 01, 2021 6:10 pm

Yes, fairly obvious that most everything can be installed incorrectly or have wrong, worn, or defective parts, especially when nobody bothers to read the TM's when doing it. Pitman arm clocked wrong included.

Yes, recommend that you pull the box off the truck to check and re-assemble everything using the books, especially if the PO did it or you personally didn't do it. Simple answer --- no, you cannot do it properly if you leave it bolted to the frame with the motor a few inches away (and the books tell you this).

Steering is like brakes --- your life depends on them. Want to go down the road wondering about it? Not me, and not me sharing the road with you. It's dangerous enough out there already.

Like the wise man once said --- "Trust, but verify."

RonD2 · Post by **RonD2** » Sat May 01, 2021 7:00 pm

By the way, a few years ago there was apparently some seriously defective sector shafts sold on the market. Catastrophic failure of steering. Supposedly the maker did a recall. You can search posts for it. Suggest when you open your Ross box you be certain that you don't have one.

See this: http://www.omix-ada.com/media/Steering% ... Recall.pdf

Good luck!

JeepdaddyRC · Post by **JeepdaddyRC** » Sun May 02, 2021 10:18 am

Thanks Ron. Even though it did not say M38A1 in the recall, I will look at the sector shaft again. Thanks for sending the info!
Update.
The PO apparently put the pitman arm on incorrectly when completing the Ross box rebuild.
You will recall: The point I felt the slight drag on the steering wheel should have been at the midpoint, because the parts are new and the grooves in the Ross box are cut narrower and shallower in the straight ahead position. Unfortunately, the tires were NOT pointed straight ahead when at the midpoint. They were about 10 degrees to the left.
Per the Ross Maintenance Manual, page 13:
https://www.keepandshare.com/doc/499400 ... 0-meg?da=y
I removed the pitman arm and moved it one spline. This changed the ball position (and moved the drag link) 10 degree and centered the wheels.
The steering feels much better, and for the first time since I've owned this M38A1 it returns to center when coming out of a turn!

oilleaker1 · Post by **oilleaker1** » Sun May 02, 2021 11:48 am

Been a while since I've hung out. Still own my Jeeps though. I have had a terrible time with the new bell crank bearing kits for both my M38's. With all replaced and new like you, I could shift the end of the bell crank arm up and down allot. I had death wobble. Everything else was good. The "new" bearings and pin fit was terrible. I complained and got the answer that hey, that's all that is available. I took the new pin and bell crank to my friendly machine shop and had a special greaseable solid bushing made with .001 clearance to the pin, and bell crank outer diameter. I drilled and chamfered the soft bushing so grease would flow through the bushing. It fixed my problems. I did it to both of my M38's. So, see how much your bellcrank end where the drag link attaches moves up and down.

Oilly

JeepdaddyRC · Post by **JeepdaddyRC** » Mon May 03, 2021 7:53 am

Update:
The following steps had been taken to find the M38A1 wobble:
- Rebuilt steering box with new worm shaft and sector
- Steering box bolts tight to frame
- New drag link, adjusted to spec
- Rebuilt bell crank with new bearings, set to 90 degrees to axle
- New tie rod ends
- New shocks
- New spring shackles
- Tires balanced and inflated to 25 lbs
- New wheel bearings and races
- New king pin bearings and races
- Steering knuckle bearing preload set to specs
- Toe in set to specs
The wobble was still there.
After much trouble shooting, I discovered the PO had not set up the Ross steering box correctly. The point I felt the slight drag on the steering wheel should have been at the midpoint, because the parts are new and the grooves in the Ross box are cut narrower and shallower in the straight ahead position. Unfortunately, the tires were NOT pointed straight ahead when at the midpoint. They were about 10 degrees to the left.
Set the steering box to the midpoint, removed the pitman arm and re-clocked it on the splines. This changed the ball position and moved the drag link to center the wheels when steering gear was centered per the Ross Maintenance Manual.
This reduced the backlash and play at the wheels. Nice improvement and it returns to center when coming out of a turn!

WillysMotors · Post by **WillysMotors** » Mon May 03, 2021 8:19 pm

I don't think you are out of the woods yet. Your steering wheel should not be raising and falling as the wheel is turned. This suggests the bearings on the worm gear are not installed or adjusted properly.

JeepdaddyRC · Post by **JeepdaddyRC** » Tue May 04, 2021 7:26 am

Thank you.
My next goal is to raise the steering shaft jacket to access the steering gear cover shims.
I believe the up/down play in the steering shaft is a result of the stack of shims I can see.

JeepdaddyRC · Post by **JeepdaddyRC** » Wed May 05, 2021 10:02 am

Shims adjusted so no more backlash at worm gear.
Up and down movement at steering shaft eliminated and shaft turns freely.
After all the steering work completed above, there is now 1/2 inch of rotational play at steering wheel.

Post by **wesk** » Wed May 05, 2021 10:39 am

And the road test had or did not have the wobble at low speed bumps?