Differential Replacement for Firehammer
11-03-2005, 07:57 PM
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Differential Replacement for Firehammer
Hey all!
My friend just got his Firehammer in yesterday and on only the second bash session managed to fry his rear differential. He was on the gas while landing a jump. The alluminum ones from Tower are on back order. Which brands of differential will fit this car and where do you find em? How hard is the replacement?! Thanks guys!!
Matt
My friend just got his Firehammer in yesterday and on only the second bash session managed to fry his rear differential. He was on the gas while landing a jump. The alluminum ones from Tower are on back order. Which brands of differential will fit this car and where do you find em? How hard is the replacement?! Thanks guys!!
Matt
11-03-2005, 08:15 PM
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RE: Differential Replacement for Firehammer
hi are you sure its the diff could be layshaft gear skipping on diff gear when landed.i notice you will need to lock tight 3 screws that have metal plate that covers top of diff and used as support for layshaft.
11-04-2005, 07:15 PM
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RE: Differential Replacement for Firehammer
It would appear to me that it is broken. Both rear wheels spin completely freely and the gears from the pinion all the way to the diff case gears are all in good shape. When the engine is running and the throttle is applied, everythin spins perfectly except there is no pressuse to the dog bones. The diff case just sits there andf spins. Which brands of these things will work on this car? Thanks Guys.
11-04-2005, 11:50 PM
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11-05-2005, 07:00 AM
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RE: Differential Replacement for Firehammer
I haven't cracked open a firehammer diff yet but have taken apart my buddies FG diff, not a lot in there to go wrong, no pressure what so ever? Are you sure the setscrews aren't slipping? Grind a flat spot and use locktite!
11-06-2005, 11:02 PM
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RE: Differential Replacement for Firehammer
Hey Matt,
Have your friend pull the diff out and see if turning the cups by hand make it work. Maybe he will find something else less expensive that is broken than the bevel gears in the diff. The way to get the diff out:
- Remove top of shocks from shock tower
- Remove hinge pins on upper arms to free them from the rear bulkheads
- Remove dogbones (they actually fall out once the upper arms and shocks are unmounted)
- Remove diff gear protector from chassis bottom
- Remove driver side rear bulkhead (upright supporting diff)
- Remove diff by working it (carefully) side to side to remove bushing from bearing on right side or bearing from right side bulkhead
This may seem like a lot but it only takes 15 - 20 minutes.
Examine the diff closely - especially the bushings on the sides that hold the outdrive cups. Is one of them loose? If not, try turning one outdrive cup - does the other cup turn in the opposite direction? If so, then gears inside may be okay. You can take the outer diff sleeve off and inspect the bevel gears inside for missing or ground down teeth. I don't remember the exact procedure for doing that but it's easy enough to figure out from the exploded diagram.
Since the car is so new your friend may be able to get Duratrax to replace the diff (it may have been assembled poorly or be part of a bad run of parts and considered defective) under warranty. Maybe it was assembled poorly by the Chinese factory. It can't hurt to call the Duratrax customer support line and ask for a replacement under warranty. He has nothing to loose by asking.
If the diff is toast, Duratrax won't replace it under warranty and he wants to bullet-proof this part more he could drop in an FG limited slip diff. They fit great in the Firehammer (except he will also have to switch over to FG outdrive cups on the diff).
I just put in an FG 8485/05 limited slip differential in my Firehammer after toasting my diff. The driver side bushing came off the diff case and caused the bevel gear mesh to get off. Several teeth on the bevel gears were shot.
I love the new differential. It is built very well (I did the assembly myself from the kit parts).
Check out FGPerformanceRC.com (talk to Troy or Mike) or RC Hobby Nuts. Both have great prices (prepare to spend about $200 or so including outdrive cups). He will get the whole assembly with new bevel gears, hardened case and sleeve, needle bearings for the outdrives and a thrust assembly that can be manually adjusted to the amount of desired slip. He will also need to spend about $18 - $20 on a riser block that raises the rear bulkheads and lower suspension arms. I had made my own riser blocks for the bulkheads only but after getting the FG riser block that raises the whole rear suspension it makes more sense. The rearend geometry is not changed when all the lower parts get rasied up the same amount.
By the time your friend buys the Duratrax hardened sleeve and new Duratrax bevel gears he will be at the $100 mark easy. For $200 or so the FG is much better quality and design.
I will try to post some pictures next week of the new diff in my car.
Ken
Have your friend pull the diff out and see if turning the cups by hand make it work. Maybe he will find something else less expensive that is broken than the bevel gears in the diff. The way to get the diff out:
- Remove top of shocks from shock tower
- Remove hinge pins on upper arms to free them from the rear bulkheads
- Remove dogbones (they actually fall out once the upper arms and shocks are unmounted)
- Remove diff gear protector from chassis bottom
- Remove driver side rear bulkhead (upright supporting diff)
- Remove diff by working it (carefully) side to side to remove bushing from bearing on right side or bearing from right side bulkhead
This may seem like a lot but it only takes 15 - 20 minutes.
Examine the diff closely - especially the bushings on the sides that hold the outdrive cups. Is one of them loose? If not, try turning one outdrive cup - does the other cup turn in the opposite direction? If so, then gears inside may be okay. You can take the outer diff sleeve off and inspect the bevel gears inside for missing or ground down teeth. I don't remember the exact procedure for doing that but it's easy enough to figure out from the exploded diagram.
Since the car is so new your friend may be able to get Duratrax to replace the diff (it may have been assembled poorly or be part of a bad run of parts and considered defective) under warranty. Maybe it was assembled poorly by the Chinese factory. It can't hurt to call the Duratrax customer support line and ask for a replacement under warranty. He has nothing to loose by asking.
If the diff is toast, Duratrax won't replace it under warranty and he wants to bullet-proof this part more he could drop in an FG limited slip diff. They fit great in the Firehammer (except he will also have to switch over to FG outdrive cups on the diff).
I just put in an FG 8485/05 limited slip differential in my Firehammer after toasting my diff. The driver side bushing came off the diff case and caused the bevel gear mesh to get off. Several teeth on the bevel gears were shot.
I love the new differential. It is built very well (I did the assembly myself from the kit parts).
Check out FGPerformanceRC.com (talk to Troy or Mike) or RC Hobby Nuts. Both have great prices (prepare to spend about $200 or so including outdrive cups). He will get the whole assembly with new bevel gears, hardened case and sleeve, needle bearings for the outdrives and a thrust assembly that can be manually adjusted to the amount of desired slip. He will also need to spend about $18 - $20 on a riser block that raises the rear bulkheads and lower suspension arms. I had made my own riser blocks for the bulkheads only but after getting the FG riser block that raises the whole rear suspension it makes more sense. The rearend geometry is not changed when all the lower parts get rasied up the same amount.
By the time your friend buys the Duratrax hardened sleeve and new Duratrax bevel gears he will be at the $100 mark easy. For $200 or so the FG is much better quality and design.
I will try to post some pictures next week of the new diff in my car.
Ken
11-07-2005, 04:00 AM
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RE: Differential Replacement for Firehammer
ORIGINAL: hellya
Are you talking about the diff cover or the entire diff
Are you talking about the diff cover or the entire diff
See ya
Col.
