Racing differential oil

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Ya just had a set crack checked today. Got to get some more components and get another one together. Had carrier deflection before when running a welded unit. The quaife is a much more rigid unit. No cast and no windows. I also found bmc flywheel bolts from arp that have oversized shanks that are almost a press fit into the carrier. I got those going after the first bolt failure. I've found that having 8 bolts I can only get the ring gear on in one position. I'm guessing I'm matching up a half a thou. of mis machining between the ring and the carrier. So I'm very confidment in the in how rigid that is. Otherwise carrier caps are sucked down with arp studs and timken bearings at a .005 bearing preload. The diff case is all cast iron and the 2 halves together with a whole bunch or arp bolts getting full length thread engagement. I happen to have my c3 vette diff built and on an engine stand at work....I keep looking at it but it's literally 3 times the size of what can fit in the car lol.
 
If a tooth is getting ripped off there likely is gear mesh errors due the load, look up Pressure angle.

Your gears look alright static but under the load of racing likely spreading them apart so yea maybe try making them tighter so when they do push apart they still have some grab.

pinion shaft likely doing the flexing so its a limitation of the shaft dia and the input torque.
 
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Originally Posted By: thescreensavers
If a tooth is getting ripped off there likely is gear mesh errors due the load, look up Pressure angle.

Your gears look alright static but under the load of racing likely spreading them apart so yea maybe try making them tighter so when they do push apart they still have some grab.

pinion shaft likely doing the flexing so its a limitation of the shaft dia and the input torque.


So are you suggesting that I move in the ring gear to the extreme of a good contact area? Instead of a more traditional pattern? There may be some merit to that. I mean the hole point of a 9 is less pinion deflection. Are there any cons to moving in my pattern other than some irregular wear? I'm really not concerned with wear obviously.
 
Originally Posted By: Fastcompany
Originally Posted By: thescreensavers
If a tooth is getting ripped off there likely is gear mesh errors due the load, look up Pressure angle.

Your gears look alright static but under the load of racing likely spreading them apart so yea maybe try making them tighter so when they do push apart they still have some grab.

pinion shaft likely doing the flexing so its a limitation of the shaft dia and the input torque.


So are you suggesting that I move in the ring gear to the extreme of a good contact area?


I think he is suggesting you find a way of measuring the deflection on the pinion shaft to see where the teeth run when in actual use.
Once measured, you can, then, use this to setup the diff such that the teeth are in contact where you want them to be in contact.
 
I think that's impossible. Other than calculating engine torque through say 2nd or third gear and using a torque multiplier on the pinion . However I would be doing this with the diff split in half loosing all the ridgidity that the large cast iron half provides. Not to mention I would get to see what kind of fixture I could destroy in the process lol
 
Originally Posted By: Fastcompany
Ya don't get me started on how I explain to the drivers they need to match revs on downshifts.....even with a dog box. The end result of this is going to have to be custom ring and pinion made. Can't wait to see what that's going to cost.glad it's not my coin


I was assuming that they already understood the importance of rev matching on downshifts.
Silly me.
 
A bit off topic, but Max Verstappen had never heard of heel and toe before.
wink.gif
 
Lol fortunately the gear boxes are strong. the stock porsche boxes on the other hand don't take kindly to 3-2 downshifts that lock the rear wheels up. The other downside to that in a 911 is they slide and spin all over the place when they make that shift.
 
Anyone have an opinion on rem treatment or cryotreatment? Had gbox put together a 915 box that was rem treated and blew up but I had a feeling it was set up wrong and wasn't due to the treatment.
 
If anyone is curious I'm getting the differential back together now. It was out at metal testing. The ring and pinion are made out of 8140. Hardness was 62rc it was tempered twice down to 57rc then cryotreated. Cars getting loaded Wednesday to go to Blackhawk so we'll see what happens. It was advised again to use 9130 but that just doesn't fit our time frame or budget for these cars. It probably will after this one breaks though lol.
 
Ok half a win here. Ring and pinion held through a weekend. However an issue I thought was resolved isn't. The car broke 2 differential stub axles during the weekend on separate sessions. I now have a batch of stubs being tested and I'll see what my heat treater can do for me on those. The car is running slip yoke half shafts with a u joint on each end. I found out early last year the suspension would put the ujoints in a bind on a hard turn and it was breaking my stub axles. I was able to tell this was happening due to fasteners rubbing together when there was approximately 1/8" clearance while static. I corrected the suspension and we had a couple races without a stub failure (diff was still breaking lol) fasteners are no longer rubbing so no flex just pure over torquing now. What's funny is there were 2 different stubs that broke. One new one old. The old one looked like it must be too hard it shattered into about 20 pieces. The new one looked too soft as the center of the fracture was raised and twisted. Good stuff.
 
Originally Posted By: thescreensavers
If a tooth is getting ripped off there likely is gear mesh errors due the load, look up Pressure angle.

Your gears look alright static but under the load of racing likely spreading them apart so yea maybe try making them tighter so when they do push apart they still have some grab.

pinion shaft likely doing the flexing so its a limitation of the shaft dia and the input torque.


I realise I'm late to the party, but..

If it is this, can you 'peg' the diff ?

Land Rover crown wheels are notorious for deflecting under load, so one work around is to add an adjustable bronze thrust block on the back side of the crown wheel.

Here's a link. http://www.ashcroft-transmissions.co.uk/...egging-kit.html
 
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