diff help

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crawlercrazed

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ok guys, so i bought a used firehammer and it needed a diff rebuild, i bought the plastic fg diff housing (fg06064) and the fg diff cover (fg6065). well i took the old one all apart and replaced the broken housing and put all the washers and gears back how they came out. i also put team fast eddy 10k diff oil in it.

on my first run it was ok for about 10 minutes of non bashing. just to get used to it. then a crunch and bad gear gringing noise. i shut it off and a couple motor mount screws came loose. tightened em up on off i went. still noise.. i found that my diff isnt like it was when it first started up????? i put the diff apart n put back together twice making sure all washers n gears were where they should be. it leaks oil as well.

my question is though, how can the diff go from acting locked to not acting locked with this grinding noise.... please help!!
 
crawler: when you have the diff out and rotate the outdrives on each side (opposite motion for diff movement), is it smooth or is it grinding? As for the leaking, I cannot recall if the housing has any sort of seal around the diff cover sleeve (giant o-ring or something).

Also, are you certain the grinding is coming from the internal differential gears and not the outside layshaft gear and differential gear?
 
it was smooth before i put it back in.. i read up on the leaking issue im goin to the auto parts store n buyin some thick grease.

when i got the fh all back together it was nice n quiet. no grinding, i bashed a little n the grinding came back. i think im gonna take it all back apart again tomorrow.
 
Are you sure it is the internal diff gears?..the reason I ask is you said you had loose engine mount bolts or screws....Could very well be you do not the the transfer gear on the lay shaft to the diff out side gear meshed correctly.......as a note the firehammer rear end has to much flex in the chassie pan...causing the gears to seporate when running on rough ground........You need to do the chassie mod............
Can you spin 1 rear wheel by hand? do you feel a bind? or ginding? If not then it is the
chassie flexing.....or incorrect gear mesh....Slawhammer
 
slawhammer said:
Are you sure it is the internal diff gears?..the reason I ask is you said you had loose engine mount bolts or screws....Could very well be you do not the the transfer gear on the lay shaft to the diff out side gear meshed correctly.......as a note the firehammer rear end has to much flex in the chassie pan...causing the gears to seporate when running on rough ground........You need to do the chassie mod............
Can you spin 1 rear wheel by hand? do you feel a bind? or ginding? If not then it is the
chassie flexing.....or incorrect gear mesh....Slawhammer
Click to expand...

im sure its the internal gears. if i lift the rear end up i can spin one wheel and the other doesn't spin, then i hear grinding, feel binding and the other side spins. when i assembled the diff i made sure everything was good before i filled it and put the housing on. after i got it all together it ran beautifull . then all this happened
 
yup ..its the diff internals then..sorry for your luck..mine is not much better...
ever time I run i brake some thing myself......
Ok now as to the diff internals...,,you may have to add 1 or 2 disc shims..there like washers....I have found the duratrac internals are to sloppy and move to much....
you want every thing snug..very little play for the parts....you can take a alum soda
pop can and make a shim..copy 1of the other washer....and add that to the internals..
Make sure the gears have very little movement back and forth for any play....
you can do all that with out any grease to check things out....If feels good then fill
up with grease and put the cover back on....Slawhammer
Ps did your dog bones slide to much in the cups? causing the diff drive cups too move out enough to drop a washer inside?
 
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see i thought thats what it is but i figured someone on here has maybe had that problem. can i just jb weld it all together?? or is that a bad idea??
 
I would say get another set of diff internals..ther cheap enough...39.95
as to Fg internals...ther like close too 85 bucks just the internal gears and then you need the drive cups inner & outer if you go FG so I would say about 125 bucks give or take
a couple dollars......stay with duratrac diff internals......I my self just got a second set
from another member here in LSF...slawhammer
 
jb weld the internals to make it a locked diff permenatly??? ill tear it all apart tomorrow and try and add a couple or more shims.... the gears looked fine when i tore it apart earlier
 
I guess you could JB Weld the internals....I never have..I figured it would not hold
together for my application ...the way I run my car....I am hard on stuff...not as to hitting some thing too say..But I run 90% of the time WOT....wide Open Throttle....
so with that said your going to do some damage some where.....Slawhammer
 
I just put the firehammer dif case in my fg with fg internals. pretty cheap at tower and it is rubber sealed. that said, the washers to hold the sleeve on were too small and I had to add bigger washers. I would have said the layshaft gear myself. I have had a noisy set on my semi since I owned it, until this weekend
 
ok heres an update.. i went to local autoparts store got some diff grease and washers... got home and tore the diff all apart, cleaned it. added washers where the spacers were ( no slop between internals) added grease, damn near like locked. put it together in the truck. checked the play, still a lil noisy. checked gear mesh between diff n the little gear, slop... loosened engine repositioned it. locktited all bolts tightened engine down. no slop no noise.... yea i gotta do the screen mod and the chassis mod still.. so i gotta go t the local park to run it and hopefully it goes well. neighbors are having a hannah montana birthday party so i didnt wanna be rude and run it in the back yard. ill update later. untill then what goo stuff do you use for the screen mod on the engine?????
 
crawlercrazed said:
ok heres an update.. i went to local autoparts store got some diff grease and washers... got home and tore the diff all apart, cleaned it. added washers where the spacers were ( no slop between internals) added grease, damn near like locked. put it together in the truck. checked the play, still a lil noisy. checked gear mesh between diff n the little gear, slop... loosened engine repositioned it. locktited all bolts tightened engine down. no slop no noise.... yea i gotta do the screen mod and the chassis mod still.. so i gotta go t the local park to run it and hopefully it goes well. neighbors are having a hannah montana birthday party so i didnt wanna be rude and run it in the back yard. ill update later. untill then what goo stuff do you use for the screen mod on the engine?????
Click to expand...

Just use shoe goo or an equivalent.
 
so i got home from a local 1/8 scale dirt track... i need to get the fg to hpi wheel adaptors and get the mx dirt tires and baja rims on this thing. the cheap 23cc engine...sux a$$.... i want a bigger engine with more torque.

after an hour of bashing, the muffler screws came loose, and the noise came back.I HAVE TO DO THE CHASSIS FLEX MOD!!!! and i have to hook up some kind of return spring cuz the carb was sticking open every once n a while...
over all though i had fun.

besides the fg to hpi wheel conversion are there other options with good dirt tires???? whats a good torquy pipe to put on it?
 
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