Tail wagging CUCV

[Recovry4x4]

I struggled for an accurate title for this thread and this was it. So for the the last 3 years I've been driving this M1008 around. I picked it up on my way to the 2009 GA Rally. When I first drove it out on Randolph Church Rd I noticed it would wiggle when you wicked the throttle and wiggle when you let off. Changing tire pressure had an effect on it but never really fixed the problem. Despite countless inspections, I was never able to find the problem. Fast forward to last week, I was again trying to find the problem thinking it was bad spring bushings or center pins in the springs. While looking up inside the spring perch II couldn't see the pin in the hole and thought I found my problem.

Yesterday I set off to replace the center pins. Much to my surprise I found them intact. I did find 2 other things.

While wrenching the U-Bolts off I was supporting myself on the brake drum when I noticed lateral movement. Actually it was quite a bit of movement. Startled I went and checked the other side and it too, had a substantial amount of lateral movement.

By design, the rear U-Bolts are subject to heavy rusting as the spring plates capture sand, dirt and subsequently water. More on this later.

So I pulled the axle shafts to inspect. No odd wear or anything like that, it just appears that whomever was in there last time, didn't preload the bearings. I pulled the square key out and adjusted them up on both sides and took it for a spin. Tail wag is all gone now. Bad on my behalf as the inspection ports showed good shoes and no seal leaks so I never opened it up. I'll do better maintenance from now on. Here's a pic of the corroded U-Bolts. Anyone with the M1008, 1028, 1010 and 1031 should consider replacing or checking these U-Bolts

 

[jw4x4]

Glad you found the problem. Those u-bolts were not far from splitsville. On a side note, we never did figure out why the brakes on the rear of the Oh-9 were toast when we got back from Durhamtown.

 

[donalloy1]

I struggled for an accurate title for this thread and this was it. So for the the last 3 years I've been driving this M1008 around. I picked it up on my way to the 2009 GA Rally. When I first drove it out on Randolph Church Rd I noticed it would wiggle when you wicked the throttle and wiggle when you let off. Changing tire pressure had an effect on it but never really fixed the problem. Despite countless inspections, I was never able to find the problem. Fast forward to last week, I was again trying to find the problem thinking it was bad spring bushings or center pins in the springs. While looking up inside the spring perch II couldn't see the pin in the hole and thought I found my problem.

Yesterday I set off to replace the center pins. Much to my surprise I found them intact. I did find 2 other things.

While wrenching the U-Bolts off I was supporting myself on the brake drum when I noticed lateral movement. Actually it was quite a bit of movement. Startled I went and checked the other side and it too, had a substantial amount of lateral movement.

By design, the rear U-Bolts are subject to heavy rusting as the spring plates capture sand, dirt and subsequently water. More on this later.

So I pulled the axle shafts to inspect. No odd wear or anything like that, it just appears that whomever was in there last time, didn't preload the bearings. I pulled the square key out and adjusted them up on both sides and took it for a spin. Tail wag is all gone now. Bad on my behalf as the inspection ports showed good shoes and no seal leaks so I never opened it up. I'll do better maintenance from now on. Here's a pic of the corroded U-Bolts. Anyone with the M1008, 1028, 1010 and 1031 should consider replacing or checking these U-Bolts

You did not include the M1009 in your list of units to inspect/replace U-Bolts? Are they not subject to this wear by differing design?

Have dropped my front bolts down. Was checking Leaf Center Pins. No problems on front.

 

[Recovry4x4]

The M1009 would be the lone exception to this issue. The Blazer ubolts are installed from the bottom so the nuts are on a spring plate above the spring. The trucks have a narrower spring spacing and their wasn't sufficient clearance to install the springs this way so they dropped the ubolts over the springs and used a ubolt plate at the bottom. That plate will retain dirt and sand around the ubolt and will subsequently hold water.

 

[dstang97]

You probably know this but you can use k20 spring plates and custom or lifted k20 ubolts. That puts the plates on top of the spring.

 

[Recovry4x4]

You probably know this but you can use k20 spring plates and custom or lifted k20 ubolts. That puts the plates on top of the spring.

This works great with a lift spring or a shackle lift. If the truck is stock height, the K20 spring plates will hit. Heres a little info with pics. Offroad Design U-Bolt Ubolt Reversal Kits GM Chevy Blazer Jimmy Pickup

DIY4X has a pretty cool upper ubolt plate I'm about to order in hopes that it will clear the frame with the stock springs.

 

[maddawg308]

Good thread, Kenny. Probably the fact that you live in Salt Air Rust City, Florida, isn't helping matters with those U-bolts. The M416 trailer I snagged from BigCase a few years back was a veteran of the FL National Guard, and ALL the bolts were in the same condition as yours. The 1" bolt that went across through the front A frame and trailer casting was, in the middle, rusted down to about 3/8" thick.

 

[gringeltaube]

.............. Tail wag is all gone now......

..which is very good! But the root cause...??

You can observe (old)cars wiggling their tail at slow speed, like when pulling to a red light; and then, when starting again. (I have seen that even in the USA....!!) Usually that's a deformed radial tire's carcass, nothing else!

So could this be the problem in your case? And the excessive play just contributing to amplify the tail-wag symptom - or even make it possible to happen and be noticed - on a relatively heavy vehicle?


(just trying to understand simple mechanical things.....)

G.

 

[Recovry4x4]

G, I'm not quite sure. The original tires had the problem as did the new ones I put on a right at 2 years ago. I've toyed with the idea of spring bushings and everything else in the rear that I thought could contribute. I did rotate some slighly unevenly worn tires to the rear when I fixed the other stuff. I plan on replacing all the rear bearings soon as I have no idea how long they were mal-adjusted. My thinking is that upon access or decell, the drums would walk from one side to the other and with the innder bearing being bigger, move the alignment a few minutes or maybe up to a couple of degrees. I'm trying to add it all up myself but the one thing I do know, the problem has been rectified.

 

[doghead]

About how much did you tighten the adjustment? (turns)

 

[gimpyrobb]

Just cause a dog is wagging his tail, doesn't mean he won't bite you!

 

[Recovry4x4]

Eric, the one side was over a compete turn. I didn't really count but subconciously noted that it was alot.

Gimpy, I expected a response like that. By the way, the steri strips are already starting to come off.

 

[gimpyrobb]

 

[dmilkman589]

on my m1009 i have serious play in my rear axle shafts. where is this adjustment your talking about? how do i access it, and will i need any special tools. thanks.