M1031 SECM ride height?

[Keith_J]

The rear shocks on my 1031 have gone out, vibration at 55 MPH despite new balance of the wheels. Looking around, I noticed a lot of rust dust on the lower leaves of the springs plus the top helper springs are nearly touching fore and aft...plus it looks like the rear end is riding lower. I am thinking the springs have taken a set due to excessive vibration from the worn out shocks. Plus the low beams seem to point higher than normal. Can anyone with a M1031 SECM measure the distance between the bottom of the rubber bump stops and the bump stop bracket? Also list how much equipment (weight is fine) you have in the back? I know places used to re-arch leaf springs..that seems like a lot of work to remove and replace.

 

[NDT]

Between the rubber bumper and axle mine shows 3.5". Between the overload spring and the slipper mine is 1". I have most of the load including the horizontal gas cylinder which is heavy as heck. Truck has true 8000 miles showing. Sounds like you have a 1" sag.

 

[cucvrus]

Springs have lost their sprung. Time for new ones. I changed a few on CUCV plow trucks this past year. They are tired after sitting on them for 30 + years. I tried the add a leaf. that is just a bandaid. Replacement ones are the way to go.

 

[Keith_J]

I have 3" on the right, 2-7/8" on the left. About 300 pounds of tools aft of rear axle plus the generator and compressor. I mounted the compressor above the generator to free up floor space.

I have seen re-arching done on springs, these are bolt-together so it should be possible. Just need to find the free height specification. I suppose the SAE 5160 spring steel can be re-arched. I found a local shop, will call tomorrow. New springs are $400+ each.

 

[Keith_J]

Found the specs, calls for a 6-1/4" arch height. This is measured off the vehicle, on a bench with a straight edge center to center on the eyes and distance from that straight edge to the top of the spring.

I am going to jack the frame to get weight off wheels and measure..

 

[dependable]

I guess you figured it out. Mine is 3.75 inches from top of axle to rubber bumper on both sides. Stock truck with gen & compressor, vice, maybe 250 pounds worth of tools & supplies, 16K miles.

 

[Keith_J]

Wow. With weight off wheels, axle hanging from springs, I measured 5-3/4" of arch. With load, the arch is 3/4" No wonder it is dragging tail.

Now when the rears are rearched, I bet the fronts will need it too. All new U bolts and bushings.

 

[Keith_J]

More heartache..the shocks I ordered are the correct type EXCEPT for the bushings..got to ream out the rubber and insert the old inner metal pieces. Special order, not returnable .
The great news is the spring re-arching is a bargain at $80 a side. New U bolts are $4 each, with nuts and washers. Made on site, just bring an old one. They also install new bushings and shot peen the springs after re-arching. Bad news is the threads are shot so getting them off will be no fun. Already soaking in PB but it took 4 foot cheater pipe on my 1/2" breaker bar to get them to move.
I should be done in a day or so. Then onto the front.

 

[cucvrus]

Introducing your best friend when working on old CUCV's. For that part any uncooperative item.

 

[Keith_J]

Yes, that and other cutting tools. My MVPA partner in drudgery broke an oil pan bolt off in the block of his M561 Gamma Goat.. Using GTAW overhead, I lengthened the bolt by 1/2" or more and heated it in the process. Toggle lock pliers turned it easily. Steel bolt in an aluminum block.
The spring shop makes any u bolt in minutes so all 4 are getting replaced.

 

[Keith_J]

No, the shocks I ordered from NAPA are not correct. Paid shipping too. Waited too long, now the truck is deadlined for another week.

 

[Keith_J]

Pulled the left spring..didn't have to cut the u bolts. Not much corrosion at all in the bottom bracket, bolts or nuts. But fought the nuts all the way as the long bolts act as torque sticks, limiting the impact gun effectiveness. Also had power outage and didn't want To run the generator while under the truck.