Racing differential oil

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Hi all. I'm actually sure this is a waste in time but I'm asking anyways. I prep 3 triumph gt6 race cars and they eat rear ends constantly. I've seen one grenade in every way possible now. Right now my set up is timken bearings complete,arp hardware complete and a quaife limited slip carrier. The last one I put together I put redline heavyweight shock proof in....made 2 laps before knocking a tooth off the ring gear. Got it apart,checked my backlash and my tooth pattern and it's right on. So all I'm certain of is my diff case is no longer flexing my bearings are no longer exploding and my posi carrier isn't snapping in half. I'm down to a ring gear that I have no choice but to run. Is there a gear oil out there that "might" help this out. I was thinking of amsoil sever gear 190 or 250. Was also wondering if making that jump should I increase backlash? Other oils with failure have been Mobil 1 and rp 75-90 and shell spirax 80-90.
 
If you've tried all those with little change, I doubt any gear oil will solve the problem but I've used it in several applications and am impressed with Amsoil so it's worth a shot.
 
I would like to hear what solves you problem, if you can remember to let us know.
 
Last time I used amsoil gearlube was when I drag raced a 2 stroke quad. The big tires I had made the wet clutch slip bad. Amsoil fixed that real good. Just never picked a fluid to solve actually detroying a component. So fingers crossed someone on here Rock crawls with a diff that is way to small and they figured something out to make it last
 
Originally Posted By: fields
I would like to hear what solves you problem, if you can remember to let us know.


Got a race in 3 weeks. So I'll know if they can last an entire weekend or not then. I got 2 and a half weeks to build another diff and pick my fluid.
 
I doubt any oil will solve your problem. Sounds like you are running waaaay more power than it's designed for. Now you know why people like the Ford 9" rear end, which you probably cant fit. Is there a conversion possible to something that will hold up?
 
Yes but with alot of mods to the chassis. It's an IRS car. A Subaru diff can fit but custom axles need made and the frame has to be cut up. The cars have historic value. As far as triumphs go these were the 2 hot cars on the circuit back in the day. Sadly I am not permitted to permanently alter anything. I recently made my own big brake kit up front buy using Toyota 4 piston callipers and 200zx rotors. It's a vented rotor vs the old solid ones. Brakes got hot enough that it ruined timken wheel bearings packed in timken racing grease and melted the piston seals out of my fresly rebiult calipers. But no brake fade though lol. The change to wilwood 600 fixed that. That was the lowest friction race pad we could get that generated that much heat.
 
Way back in the late 1970's Porsche was having trouble with the diff transaxle grenading on the 935's...these cars could produce north of 800 HP and tons of torque...Tried a lot of different gear lubes and finally settled on Swepco 201...problems solved. Bruce Andersen of Porsche fame used to tell that story quite often...Swepco 201 is a staple in many of the older 915 Porsche style transaxles to this day. Might be worth a try....I run it in my Austin Healey 3000 and my older Porsche 911...quiets them down too. FWIW i run Miller's 75w110 or Amsoil 75w110 in our Porsche 996 cup and 964 cup race cars. They do well and look great when we do the annual inspections...I have rebuilt the 964 box once and replaced a few bearings in the 996 cup...Those cars are raced pretty hard.
 
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All of our Porsches get 201. We started running it in our t44 transaxle in the GT40 as well. Actually never thought of dumping it in a rear end. Might be worth a shot
 
And on the note of inspections I have yet to wear anything out in one of those rear ends. It's always fine until total failure. I will say I have had the most failures in the car with the dog box. No clutch shifting shock loads in pretty hard. The other car has a Richmond 5 speed and can usually make 2 or 3 events without failure. Both cars making approximately 200 hp with solid hub clutches
 
I don't think a lube failure is causing a tooth to break off of the ring gear. It sounds more like a metallurgical,or other issue with the ring gear. Can you take the new gear to a heat treating shop, have them test the hardness and possibly re-heat treat it? Just clutching at straws.
 
I can have it tested for sure. Was just discussing this today. Typically if you are to have a part heat treated you do it right before finish machining. And I've already talked to the big manufactures out there and they won't give up any of the heat treating numbers. I am not good enough to say what rc to what depth. My guess right now based on how they wear is very hard and treated to far down at that hardness. Maybe even thru hardened to one spec. I know one had the bolt holes slightly messed up and I ruined a carbide tap trying to clean it up.
 
Originally Posted By: Fastcompany
I can have it tested for sure. Was just discussing this today. Typically if you are to have a part heat treated you do it right before finish machining. And I've already talked to the big manufactures out there and they won't give up any of the heat treating numbers. I am not good enough to say what rc to what depth. My guess right now based on how they wear is very hard and treated to far down at that hardness. Maybe even thru hardened to one spec. I know one had the bolt holes slightly messed up and I ruined a carbide tap trying to clean it up.


Pretty typical heat treat specs for gear material are usually Rc 57-62 surface hardness with an effective case depth of about .100" to Rc 50 hardness. Core hardness of the material would be Rc 30-34 or somewhere in that range. Are you using low carbon alloy steels that are carburized, or medium carbon steels that are induction or flame-hardened? I would recommend carburized low alloy steel (9310 or 8620) for the more ductile core and better controlled case properties. (But it would be more expensive.)
 
Originally Posted By: Fastcompany
And on the note of inspections I have yet to wear anything out in one of those rear ends. It's always fine until total failure. I will say I have had the most failures in the car with the dog box. No clutch shifting shock loads in pretty hard. The other car has a Richmond 5 speed and can usually make 2 or 3 events without failure. Both cars making approximately 200 hp with solid hub clutches


If you start talking about shock loading of the drivetrain, all bets are off in component fatigue life. If the dog box car fails in every race, and the Richmond 5-speed can go 2 or 3 events, that at least shows a significant difference. Is there an option to put sprung hub clutches in to try to dampen shift shock?
 
Yes and no. The car with the Richmond box runs a spec stage 4 clutch. Spec will make me a friction disc however I want it. The car with the dog box runs a tilton. Dog box shifting tends to break clutch hub springs so we only run solid hubs with that type of box. The heat numbers you gave me are what I came up for when researching axles for the car. I assumed the gears would be different. I have no idea what the current ring and pinion are made out of. There is ONE SUPPLIER FOR THR RING AND PINION. It comes from Germany with no discription other than ratio. There is a gear manufacturer right down the street from my shop but one off stuff cost thousands and thousands. At this point in time I have a couple of weeks to hope something gets the cars through an event. Typically I go with our customers to the race but he has opted to go alone without track support to this next one. I was really hoping the way I built this last diff was going to make a difference.
 
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Originally Posted By: Fastcompany
....made 2 laps before knocking a tooth off the ring gear.


If the diff is lasting only 2 laps, I don't think this is an oil problem. And for the moment, let us discount setup problems.

This sounds a lot more like the TQ of the engine, multiplied by the tranny, is simply larger than the teeth in the differential can withstand. Better materials in the gears is advised--like 4140 or 4340 and be sure to properly harden.

Now, if the diff lasted 20 laps and did the same thing, oil might be part of the problem.
 
Originally Posted By: Mitch Alsup
Originally Posted By: Fastcompany
....made 2 laps before knocking a tooth off the ring gear.


If the diff is lasting only 2 laps, I don't think this is an oil problem. And for the moment, let us discount setup problems.


Are we also assuming they know how to downshift properly?
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But yeah, oil doesn't seem like it's going to solve this one.
 
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
 
As long as you are sure there aren't carrier deflection issues, it just sounds like you are overstressing a component. As far as ring gears go, we often used "soft" gears in an attempt to reduce stress fractures/failures. Increased hardness equals fractures. Better a gear "give" a little rather than shatter. If you are truly limited to only one part number for a gear, run the best of what you got. Magnaflux/MPI, or at least dye check, every gear before it gets installed. Between events, pull the diffs, repeat. Scary the stuff you see at the root on the drive/convex side of a ring gear tooth.

I will spare you the "throw a 9" in it" comment.
 
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