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Thorp ball diff questions

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I recently scored a couple of Blackfoots locally, and low and behold, one had a Thorp diff, countergear and dogbone setup installed. This is my first Thorp item. I dreamed about them when I was a kid and never thought I'd get one. The entire gearbox was packed with a thick black grease. What new grease is recommended? Tamiya ball diff grease would be my first guess. How were Thorp diffs adjusted? Is it the usual method of locking the outdrives while tightening it just enough so the gear can't be spun by hand? Are they fairly durable or should this just go in a shelf queen as a neat vintage hop-up?

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I recently scored a couple of Blackfoots locally, and low and behold, one had a Thorp diff, countergear and dogbone setup installed. This is my first Thorp item. I dreamed about them when I was a kid and never thought I'd get one. The entire gearbox was packed with a thick black grease. What new grease is recommended? Tamiya ball diff grease would be my first guess. How were Thorp diffs adjusted? Is it the usual method of locking the outdrives while tightening it just enough so the gear can't be spun by hand? Are they fairly durable or should this just go in a shelf queen as a neat vintage hop-up?

Hey there.

Yes, Tamiya Ball Diff Grease, Ceramic Grease, or any of the top brands are fine also. I personally use my Thorpe in My Brushless Monster Beetle, and it seems durable. To adjust teh diff you have to take one dogbone off, under which tehre is an allen key bolt, You hold the oother wheel and adjust the tension to desired. Its hard to adjust/check, as you have to take replace the dogbone/suspension arm, then run it, take it apart again, adjust it etc. I have mine pretty much locked out, with only minimal diff operation. Seems fine to me, although I cant say how long it'll last.

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Good info here! I have one too that I am planning on running at some point when I get that project off the ground.

OSR

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So when you take it apart to clean it, you'll find the ceneter screw will be bent. It's that way to provide a sort of locking feature so don't straighten it out or replace it with an unbent screw.

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Shodog,

What is the best way to adjust one of these things so that it will Live a long time and perform how it is supposed to?

Thanks

OSR

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I adjust mine to where it's just a smidge tighter than letting it slip. Too much slip and you will melt the gear.

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hi - can anyone confirm that this is a thorpe diff? i pulled it out of a parts blackfoot trans and almost threw it away b/c it looked pretty grungy but then realized it might be a dirt burner setup so i put it in a baggie and am considering using it in a frog build. assuming it is, although i'd assume these are interchangeable between the blackfoot, MB and frog are there any caveats to consider? also, one of the drive cups has semi-circular notches on the inside of the groves for the dogbone (elbows?). i can't tell clearly if this is mean to be this way to lock the dogbone in place but the fact it's only on one side and that it would cause it to click upon reverse has me thinking otherwise.

also - any tips on the best way to clean it up and reassemble it? i can improvise but will always take others' experience into account if i have it.

thanks!

ben

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hi - can anyone confirm that this is a thorpe diff? i pulled it out of a parts blackfoot trans and almost threw it away b/c it looked pretty grungy but then realized it might be a dirt burner setup so i put it in a baggie and am considering using it in a frog build. assuming it is, although i'd assume these are interchangeable between the blackfoot, MB and frog are there any caveats to consider? also, one of the drive cups has semi-circular notches on the inside of the groves for the dogbone (elbows?). i can't tell clearly if this is mean to be this way to lock the dogbone in place but the fact it's only on one side and that it would cause it to click upon reverse has me thinking otherwise.

also - any tips on the best way to clean it up and reassemble it? i can improvise but will always take others' experience into account if i have it.

thanks!

ben

Ben congrats! You have a Thorp Diff and you have a Throp Counter gear (the black one)! Nice score! You are right they are totally exchangeable between the Frog, Brat and Blackfoot because they share the same chassis gear box design. Can you take a picture of this semi -circle in the drive cup? Not too sure what you are looking at... Might be a worn cup or something else. Pic will help!

OSR

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great! i'm attaching a couple close-ups of the part in question. i saw what i think is the same part on jim's toy + hobby ebay store so i ordered it. can't hurt. but still curious...

here's what i ordered: http://www.ebay.com/itm/380548005310

hmm. image uploads not working. will try posting and linking via URL. ok, that worked...

8342976139_883d59123d_b.jpg

8344036110_4e39ec99ca_b.jpg

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Wow, somebody "loved" whatever truck that diff was in... yeah, those are supposed to be just straight slots. That's wear. I have a set of RC10 rear axles that look about the same. If the outdrives can look like that, and the rest of the diff is still fine, you start to realize why these setups are so highly prized among us Blackfoot devotees.

One warning - the gear ratio is different between the Blackfoot and the Frog. I know you can change the pinion gear to make it work (can't remember what pinion is needed), but make sure everything lines up and meshes nicely so you don't chew up the counter gear.

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great! i'm attaching a couple close-ups of the part in question. i saw what i think is the same part on jim's toy + hobby ebay store so i ordered it. can't hurt. but still curious...

here's what i ordered: http://www.ebay.com/itm/380548005310

hmm. image uploads not working. will try posting and linking via URL. ok, that worked...

8342976139_883d59123d_b.jpg

8344036110_4e39ec99ca_b.jpg

Ya that is worn out! Those are supposed to be straight! If you can't find those drive cups on ebay then I would drop a little weld to fill in that curve for a temporary fix.

OSR

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i've been pondering something all morning. why didn't thorpe name these 'filth warmers'?

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