Thanks for the pics. ?
Big Rock GPMRacing - Wheel Driveshafts
- Thread starter xertian
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How much for all 4 corners?
jondilly1974
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I got a little bit more time to wrench around tonight and made a few more observations...
1. The grub screw/set screw mystery is definitively solved. How the hell did I miss these depressions in the output shafts? I never even noticed them before even after swapping 5 rear shafts and 1 or 2 fronts. Clearly the GPM set screws engage these dimples and will provide greater holding power in conjunction with the end screw. So the GPMs are a significant upgrade in the attachment to the diff output shaft. That said, I don't think anyone was having problems with that particular aspect of the factory shafts before so...
2. My Hot Racing hex adapters in the rear were sufficiently deformed to not fit over the GPM axle shafts. This scared me at first as I thought the GPM axles were out of spec or otherwise going to be useless. I tried the OEM 14mm hexes on the GPM axle shafts and they fit snugly, but without issue. In other words the GPM tolerances are just fine, it's my HR adapters that are soft and have deformed after ~12 packs. My front HR adapters were less deformed and slid onto the GPM axles with a bit of a struggle. The HRs that came off the back will need to be deburred or filed down before they will fit back on the truck. If you have these HR adapters don't panic if/when they don't fit.
At full upward travel of the rear arms the the white O ring is in contact with the slider at both ends of the slider, but not compressed. There's less than 2mm clearance between the slider and GPM cup when articulated like that, axle end looks about the same. I'd imagine a hard landing with soft arms could allow for some contact there. This is definitely one of those things that will be borne out in use. On the bench it looks OK to my untrained eyes.
1. The grub screw/set screw mystery is definitively solved. How the hell did I miss these depressions in the output shafts? I never even noticed them before even after swapping 5 rear shafts and 1 or 2 fronts. Clearly the GPM set screws engage these dimples and will provide greater holding power in conjunction with the end screw. So the GPMs are a significant upgrade in the attachment to the diff output shaft. That said, I don't think anyone was having problems with that particular aspect of the factory shafts before so...
2. My Hot Racing hex adapters in the rear were sufficiently deformed to not fit over the GPM axle shafts. This scared me at first as I thought the GPM axles were out of spec or otherwise going to be useless. I tried the OEM 14mm hexes on the GPM axle shafts and they fit snugly, but without issue. In other words the GPM tolerances are just fine, it's my HR adapters that are soft and have deformed after ~12 packs. My front HR adapters were less deformed and slid onto the GPM axles with a bit of a struggle. The HRs that came off the back will need to be deburred or filed down before they will fit back on the truck. If you have these HR adapters don't panic if/when they don't fit.
At full upward travel of the rear arms the the white O ring is in contact with the slider at both ends of the slider, but not compressed. There's less than 2mm clearance between the slider and GPM cup when articulated like that, axle end looks about the same. I'd imagine a hard landing with soft arms could allow for some contact there. This is definitely one of those things that will be borne out in use. On the bench it looks OK to my untrained eyes.
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jondilly1974
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My HR 17x10mm hubs deformed quickly too. I just dremeled them lightly to make getting them on/off easier.
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- #68
30 seconds with a rat tail file did it for me. If I need to remove any more material in the future I'll definitely break out the dremel and a small carbide burr.
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- #69
I got 2 (8000mah) packs through these things this weekend without issue. I managed to get on the skate park for about 5 minutes between groups of children and their glaring parents for some 2-3 foot air (I'm new at this) but nothing that would impress any of you here. The rest of my time was highspeed runs in relatively flat terrain and highspeed/low air launches off a small berm. At this point I guess it's just a waiting game to see how they hold up.
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- #71
Time will tell if they are reliable. I've got to be honest, with the general skepticism around GPM I'm still expecting them to spontaneously combust at any moment.
I did grease the slider splines heavily with some automotive bearing grease. I'd recommend not to skimp on that.
slick2500
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AimlessRC
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What? Lol.
The Hardest part of this install were the cups to the out-drives. For some reason, mine were super tight tolerance on the spline and have no threaded hole or grub screw!
I took an old out-drive and pounded it into the splines on the cup, then used a pin punch to knock it out. 3 or 4 times doing this and a little filing and they slipped right on. Notice the bit of shaved steel down in the bottom of the cup.
They are a bit larger compared to the hot racing ones. Splines are much deeper on the slip joints and the balls and sockets are a bit larger.
Installed mine with a bit of grease.
The Hardest part of this install were the cups to the out-drives. For some reason, mine were super tight tolerance on the spline and have no threaded hole or grub screw!
I took an old out-drive and pounded it into the splines on the cup, then used a pin punch to knock it out. 3 or 4 times doing this and a little filing and they slipped right on. Notice the bit of shaved steel down in the bottom of the cup.
They are a bit larger compared to the hot racing ones. Splines are much deeper on the slip joints and the balls and sockets are a bit larger.
Installed mine with a bit of grease.
AimlessRC
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This is a Granite but they have identical diffs. Mine have the dimples.
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- #78
BUSTED!!
I lost one of the GPMs already. It looks like the wheel axle assembly broke at the holes allowing the linkage bits to fly off. I couldn't find any parts so the slider is gone as well. That was on pack #3. I'll get some pics of the breakage. Surprisingly this was on a front install, not the back which is what I would have expected.
I lost one of the GPMs already. It looks like the wheel axle assembly broke at the holes allowing the linkage bits to fly off. I couldn't find any parts so the slider is gone as well. That was on pack #3. I'll get some pics of the breakage. Surprisingly this was on a front install, not the back which is what I would have expected.
Uz3r
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Thanks for sharing your journey guys - not sure if its heading to a good outcome or not but its been interesting following you.
