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IFS Problems on Tow Rig

mtnman210

mtnman210

1/2 ton status
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Major problems on my tow rig:doah::doah::doah::doah: The rig is a 95 Chevy K3500 dually, long bed, crew, 4in lift, 30's, 454, etc....

about a month ago I was stuck in a deep snow in the driveway. Put it in 4hi to back out and still couldn't move so I tried 4lo and BANG! Broke the pass side cv axle. No big deal I just figured it was it's time to go. Through in a replacement and went to back up and BANG AGAIN! broke almost identically to the first time. It's pulling the "ujoint" part of the cv out, where it connects to the flange on the housing, and breaking that "hub assembly" on the flange. Sorry for the quotes I have no idea the actual names for the cv axle parts---bare with me.

Fast forward to this afternooon, back in SoCal, so nice and warm and dry. Pulled out on the street put it in 4hi to test it. Drove forward and backward and no issues, put it in 4lo and the whole truck torqued up to one side and BANG. SAME THING!!!! same side same breakage as before. This time something twisted as well, because I also broke a section of one of the fins on the housing and cracked the cross-member that the torsion bars attach to.

I've obviously got something binding or seized completely. Any ideas on where to start? I've never dealt with this IFS stuff so before I dive into it, I thought I'd check for suggestions?
 
I'm not all that well versed in IFS despite my Ford 3/4 ton having one. The only time I had anything like that was when the pivot bolts worked loose where they attached to the frame.

Sounds like either you have a problem at the ball joints letting the whole hub assembly twist enough to bind that joint, or the whole axle is twisting because the center pivot is not solid.
 
Could be a couple things:

1. If your torsion bars are over cranked it will affect your CV axles and increase the wear on them, combine angle with torque of 4LO..could break.

2. I remember reading somewhere that on an 88-98 8lug GM with a suspension lift that MANY lift kits offset the differential...I believe to the left. This would make the right shaft too short and they will continue to break under heavy torque.

4 wheel and off road magazine had the same problem with their 91 K2500 they had.
 
mtnman210 said:
Major problems on my tow rig:doah::doah::doah::doah: The rig is a 95 Chevy K3500 dually, long bed, crew, 4in lift, 30's, 454, etc....

about a month ago I was stuck in a deep snow in the driveway. Put it in 4hi to back out and still couldn't move so I tried 4lo and BANG! Broke the pass side cv axle. No big deal I just figured it was it's time to go. Through in a replacement and went to back up and BANG AGAIN! broke almost identically to the first time. It's pulling the "ujoint" part of the cv out, where it connects to the flange on the housing, and breaking that "hub assembly" on the flange. Sorry for the quotes I have no idea the actual names for the cv axle parts---bare with me.

Fast forward to this afternooon, back in SoCal, so nice and warm and dry. Pulled out on the street put it in 4hi to test it. Drove forward and backward and no issues, put it in 4lo and the whole truck torqued up to one side and BANG. SAME THING!!!! same side same breakage as before. This time something twisted as well, because I also broke a section of one of the fins on the housing and cracked the cross-member that the torsion bars attach to.

I've obviously got something binding or seized completely. Any ideas on where to start? I've never dealt with this IFS stuff so before I dive into it, I thought I'd check for suggestions?
Click to expand...

Ho wmuch do you think it will cost to repair the damage at this point?
Maybe it's time to Straight Axle it.:dunno:
Do you have that heated element 4wd system?
IIRC it has a system that binds both sides so you have 4wd, and that part dould be the problem.
Either that or the hub on the side that is breaking is bound up.
Or, maybe someone replaced the rear axle and the gear ratios are different.:dunno:
I reread your post, you have 4" lift, could there be binding from the angle generated by the lift?
And why 30's with a 4" lift, I thought stock was 30's
 
It's the stock electric actuator not the heated version. And it was new as well.

New outer wheel hubs

I'll check all the mounts and the top pivot mount on top.


Up to the first break last month, I've never had a problem in high or low. Ive towed throughsandy washes in 4lo and second gear, towing the blazer without troubles.
 
mtnman210 said:
It's the stock electric actuator not the heated version. And it was new as well.

New outer wheel hubs

I'll check all the mounts and the top pivot mount on top.


Up to the first break last month, I've never had a problem in high or low. Ive towed throughsandy washes in 4lo and second gear, towing the blazer without troubles.
Click to expand...

Do you need the lift?
I bet it's the source of your trouble.
 
I'd like to keep the lift, especially since I just bought tires 2 weeks ago and I don't have any of the original parts. I'm sure it doesn't help things but its only a 4in with the new knuckles. As I mentioned I've had the truck 2 years now and hadn't had any problems up until now.
 
Post a picture of your cv angles. Also, was this the first time you used 4x4 on pavemen? It sounds a lot like you have a different gear ratio in the front diff. Does your lift kit have extensions on the cvs? The shafts may be too short, especially if the differential is shifted off to one side.
 
I've got the new cv, I'll post pictures when I put it in and see what everyone thinks of the angles.
 
Got the new cv axle in last night. Didn't get much time on it as I had other things going on but I did find what is either the problem or one of the problems. The cv itself is too short. The balls are sticking out of the hub that attaches to the housing. So It has very little engagement. I could see with the torque of 4lo how it would just pull out. So I need to look for a set of spacers and that should fix that problem. I still didn't have to time to check for binding yet but I should get to that in the next couple nights.
 
Many of the lift kit manufacturers include spacers in their kits for the CV's check with the manufacturer of your lift.
 
The diff is dropped right?

What brand lift?

Did you put the lift on yourself?
 
Still, good to know as there have been some skeezy designing of lift kits in the past.

Rancho's original 4" GM IFS lift was pretty much pulled from the market it was so craptastic.
 
Yes the lift has the drop knuckles and 4in blocks in the rear.

The torsion bar cross member says procomp.

I did not put the lift on, it was on when I bought the truck
 
ProComp eh...any idea how old the lift is?

Their earlier stuff was crap. Had a buddy with one of their lifts on his Tahoe back around 2000 and the subframe pieces kept rattling loose and he'd get weird issues as his ENTIRE FRONT SUSPENSION started jiggling around loose.

Drop knuckles though...that sounds like a newer setup. The differential itself is dropped too, correct? Have heard of folks not putting the diff drop parts on or installing them incorrect. That would definitely put the CV's at a bad angle. 2" makes them iffy...4" would be horrible.

Call ProComp and ask them. Bet they could tell you what should at least be there or how to identify the whole setup.
 
I've got a little update on this. I got everything back together as I needed to pull my rig for a trip. I just stayed in 2wd so there wouldn't be any problems. Well it was my first trip with my new slide in camper. On the way home I bottomed out the whole rig on a bump going down the freeway. When I got home I found the axle shaft pulled out AGAIN (the same side as previous problems) :mad3::mad3::mad3: but this time in 2wd. Luckily nothing broke, the only casualty was a torn cv boot.

Well when I went to replace it I found THIS.... I don't know if this was the "MAIN" cause of all the problems but I'm sure it had a contributing factor.

This is at ride height. The angle isn't bad but notice how far out the end inner cv is out of the "hub"
p3162278.jpg


p3162279.jpg



Well I ordered up some spacers and they seemed to help.
p3162280.jpg


p3162281.jpg


p3162281.jpg



Haven't tried it in 4wd yet. I'm going to put in up on some jack stands this time and try 4wd before I try it on the ground.
 
Haven't tried it in 4wd yet. I'm going to put in up on some jack stands this time and try 4wd before I try it on the ground.
Click to expand...

Unless its going to go father in when you load it, I would not bother trying it.
That does not look like its in far enough.
More shims might fix it, but I'm not sure.

Any chance its just the wrong axle?
 
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