Breaking in diffs

[Reuben]

After you rebuild your diff, do you have any processes of breaking them in? making them race ready? or just let it run itself in on the track?

what methods have people tried? and to what effect?

I usually stick to the run it in on the track rather than on the bench, as the diff will never be diffing as much as it does if you hold one wheel. But ive tried running it in and it makes the diff good from the word go.... But is its life expectancy reduced at all doing this?

what prompted this is that ive just seen a "Diff break in tool" which is made by muchmore and its just a tyre sander with an adaptor to attach it to a wheel nut and spin the diff up at a constant speed to run it in.......

[darrenoakley]

I used to do it the spin up way but was talking to Terry one day and he made me realise that it would never spin at that rate on the track, unless of course you got one wheel stuck and continued to nail the throttle. I then run in on the track for a few rebuilds but forgot to check it after running in and it was real loose. I now have gone back to the bench method as I do it all in one hit and don't forget .I think holding one wheel maybe speeds up the process. As for if it's bad for the diff I don't know.

[mattsedgley]

Breaking in a diff on the bench is important in my opinion,

when you're breaking one in on the bench you never use more than half throttle, you do completely stall one wheel, with that in mind it is very similar in action to how the diff reacts on the track if you consider your stopping one side and then the other, the diff has to work both ways when it's in the car. the key thing is not to do it for too long, I made this mistake often at the start. you only need to do it for 30 - 40 seconds, any more and the diff becomes hot, and can tighten.

it's not uncommon to a diff to run in the 25 - 30 degree zone, however running in on a bench can quickly generate heat up around the 50C mark..

the muchmore tool is an intersting one, it's not a tyre sander like reubes says, it's far smaller than one of those, however it fits onto the wheel nut when the car is on the MM low stand.. you then have to stall the spur, and allow the machine to rotate the diff, it's clearly the most pointless tool in the world! you can do the same by stalling one wheel as we do..

on a note about diffs it's a shame the schumacher wont fit a geared diff, as i'd love to try one, les loves the rip it gives out of a corner, i'd like to experience the same in the pooey..

anywho.. I've wandered enough! Muchmore diff tool = utter sh1te IMO




it's clear the photon and Xray diffs are great, the schumacher diff is good, not having the ability to adjust it's tension when it's in the car is a little annoying.. however the grub screw that holds the compression constant is really nice..

going off piste slightly it's allways interesting when people think their diff is good as they turn one rear wheel, the wheel, or more importantly the rubber and foam around it take out most of the feeling, grab hold of the outdrives as they come out of the bulkhead and turn those, thats how you really tell if the diff is still smooth.

wandering even further off topic from reubes post (i'm sorry mate!)

Generally, if my car suddenly goes off for no apparent reason, the first thing i check is the diff.. I find it can tighten up in just one run and go from great to sh1te really quickly... typically the car starts to oversteer..

[lesbaldry]

Its always best to use a good quality diff grease,the thicker the better IMHO,so after a rebuild the thick grease will make the diff feel a little "gummy" or tight unless its run in a little on the car befor use (to dissipate the excess grease off the plates)or the car might well change handling characteristics during the race as it "beds in"....Ive never had any premature wear issues with on the car running in,but I have seen some people hold one wheel and stupidly spin the diff up near flat out, I think this puts unnatural speeds and load on the little side thrust bearing and may cause damage in the long run??

Reuben,you will realize what you have been missing now you have the second best diff out there..... ;)lol.....Get that gear diff in for a try,I love "the feel" it gives,but it might be a "Marmite" for some people??

[Reuben]

super stuff

[yellowshark]

We generally run the XRAY diff in on the track. 2 slow laps,into pits & tighten up 1/8th turn; repeat until we get to the desired tightness.

Last time we ran in on the bench; can't remember exactly but probably 5 or so secs at 1/4 or so throttle on both wheels; then tighten up 1/8th turn and repeat etc. I have no idea if this was right but diff felt fine. Cannot comment on difference on longevity as we have not done many races on that diff.
Personally I would prefer to run in on the track but that is really an emotional perspective rather than any scientific investigation - ie it is probably closer reality (again an emotional point) so therefore potentially the best way.