- Joined
- Oct 31, 2014
- Messages
- 444
Well, my project of the day was replacing the shock absorbers on the GMC motorhome.
Much more involved than at first anticipated. Even required getting some new tools to ease the process.
The rear suspension of these RVs is an air suspended double axle bogie that is a bit fussy as to how you jack it up. Can't just put a jack underneath the frame anywhere, it has to be at specified lifting points or else you risk bending the frame or skewing the air suspension.
First off, the lug nuts are specified to be tightened to 250 ft lb., so at least that much is required to remove them I discovered that was much more than any of my existing impact tools was capable of. I beat on the lug nuts with the tools I had and got several nuts loose but the rest were stubborn, Although I am somewhat skeptical of Freight Harbor tools, they have some well-reviewed higher power impacts that seemed worth a try.
Purchase #1:
While I was there I also figured that a 16.5" steel wheel and tire combination would be pretty heavy and awkward to manage dismounting and mounting back on the RV - so I got a 'tire lifter' that is supposed to lift 1/4 of a 5000# car (well, maybe) but should certainly lift at least one disconnected wheel.
And (here's the "shop project part" of the post) according to the GMC user's group it is easier to raise the rear wheels if you have a shim to hold the bogies up a bit so less jacking is needed. It's just a piece of 3/8 x 2.5" HRS about 12-14" long. I didn't have any 3/8" bar stock that narrow so I took a piece of 4" that I did have and sheared it down to 2 1/2" on the ironworker. Faster than plasma cutting and less chance of starting a forest fire. That's a concern here right now - but that's another posting.
So, fully tooled I attacked the motorhome.
I lifted the coach with a floor jack enough to take some weight off the axles and hold it up for further processing. The HF impact wrench actually spun the nuts off in record time, like they were only hand-tight. Wow! Time will tell how long the tool will last but for this need it filled the bill.
Once the lug nuts were a bit loosened I jacked it up far enough to insert the shim. Easy peasy. Then deflate the airbag to reduce strain on the bogie arms and jack some more until both tires were off the ground.
The tire lifter worked like a charm to manhandle the wheel/tire off the rig, the replacement of the shock absorbers went fairly straightforward and everything went back together quite nicely.
The whole shebang looked like this mid project. You can just see one end of the lifting shim (the red bit) mid photo. The new shocks had pretty tough springs inside them so a strap clamp was used to compress each shock until it fit in the the mounting holes. That's the orange snake in the picture.
Finally, torquing the lug nuts back to factory spec (250 ft lb) was beyond the capability of my existing supply of torque wrenches - so I got them to 150 and ordered a wrench with 250# range. They'll hold at 150 and be at 250 later.
First shock took two hours, subsequent about 20 minutes each. Feels like an accomplishment!
Much more involved than at first anticipated. Even required getting some new tools to ease the process.
The rear suspension of these RVs is an air suspended double axle bogie that is a bit fussy as to how you jack it up. Can't just put a jack underneath the frame anywhere, it has to be at specified lifting points or else you risk bending the frame or skewing the air suspension.
First off, the lug nuts are specified to be tightened to 250 ft lb., so at least that much is required to remove them I discovered that was much more than any of my existing impact tools was capable of. I beat on the lug nuts with the tools I had and got several nuts loose but the rest were stubborn, Although I am somewhat skeptical of Freight Harbor tools, they have some well-reviewed higher power impacts that seemed worth a try.
Purchase #1:
While I was there I also figured that a 16.5" steel wheel and tire combination would be pretty heavy and awkward to manage dismounting and mounting back on the RV - so I got a 'tire lifter' that is supposed to lift 1/4 of a 5000# car (well, maybe) but should certainly lift at least one disconnected wheel.
And (here's the "shop project part" of the post) according to the GMC user's group it is easier to raise the rear wheels if you have a shim to hold the bogies up a bit so less jacking is needed. It's just a piece of 3/8 x 2.5" HRS about 12-14" long. I didn't have any 3/8" bar stock that narrow so I took a piece of 4" that I did have and sheared it down to 2 1/2" on the ironworker. Faster than plasma cutting and less chance of starting a forest fire. That's a concern here right now - but that's another posting.
So, fully tooled I attacked the motorhome.
I lifted the coach with a floor jack enough to take some weight off the axles and hold it up for further processing. The HF impact wrench actually spun the nuts off in record time, like they were only hand-tight. Wow! Time will tell how long the tool will last but for this need it filled the bill.
Once the lug nuts were a bit loosened I jacked it up far enough to insert the shim. Easy peasy. Then deflate the airbag to reduce strain on the bogie arms and jack some more until both tires were off the ground.
The tire lifter worked like a charm to manhandle the wheel/tire off the rig, the replacement of the shock absorbers went fairly straightforward and everything went back together quite nicely.
The whole shebang looked like this mid project. You can just see one end of the lifting shim (the red bit) mid photo. The new shocks had pretty tough springs inside them so a strap clamp was used to compress each shock until it fit in the the mounting holes. That's the orange snake in the picture.
Finally, torquing the lug nuts back to factory spec (250 ft lb) was beyond the capability of my existing supply of torque wrenches - so I got them to 150 and ordered a wrench with 250# range. They'll hold at 150 and be at 250 later.
First shock took two hours, subsequent about 20 minutes each. Feels like an accomplishment!
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