Quaiffe ATB diff
Discussion
Thinking about installing a quaiffe ATB diff. I have a TVR Tasmin race car currently fitted with a Jag open diff with a 4.1:1 ratio. Coming out of the twisty bits and starting off the grid I always light one wheel up which is obviously loosing time.
Anybody got any experience with the ATB in a rear wheel drive car?
Anybody got any experience with the ATB in a rear wheel drive car?
The Jap powerloc diff was the first port of call for Tasmins, however all have moved away from the Jag unit, I think the reason is becasue there isn't enough weight on the back axle in the race cars to let the diff operate correctly although I'm not 100% on that. Dave best give Graham a shout, he'll be able to fill you in more fully.
Regards
Iain
Regards
Iain
NTEL said:
Already looked into the Powerlock but almost everybody I spoke to said that due to the race cars being so light and the lower torque of the V6, they don't work properly and tend to lock a wheel up.
I though the slippage could be adjusted via the friction plates.. guess you might be better off taking to an expert here rather than here say on forums.Edited by NTEL on Wednesday 15th October 13:47
i use a 7" quaife diif in my hillclimber and previously used a viscous LSD. given that the cars approx 800kg/280brake and RWD, it probably compares with the tasmin.
the viscous tended to be 'stiffer' in its action, especially in the damp or slippery conditions, initial understeer followed by oversteer on the power. the quaife drives like an open diff, no 'tight' feeling at all, and is quite progressive as by design it never fully locks. its diadvantage is if you get a rear wheel airborne, it transmits drive to the flailing wheel as it needs some load on each wheel to give the lsd action (unlike a viscous, plated diff or locker). that said, its not a major issue as the wheels are usually firmly planted! nice and easy and vice free in the wet and damp.
i have yet to try a 'plated' lsd in this car. from what ive heard and read, they are probably the ultimate in absolute traction as they lock the drive axle solid, but they are clunky at paddock speeds and the ramps and plates do wear so the 'tightness' settings do change through its life.
for me the quaife is all things to all tracks, i cant be arsed to change diff styles if it rains ;-)
Craig
the viscous tended to be 'stiffer' in its action, especially in the damp or slippery conditions, initial understeer followed by oversteer on the power. the quaife drives like an open diff, no 'tight' feeling at all, and is quite progressive as by design it never fully locks. its diadvantage is if you get a rear wheel airborne, it transmits drive to the flailing wheel as it needs some load on each wheel to give the lsd action (unlike a viscous, plated diff or locker). that said, its not a major issue as the wheels are usually firmly planted! nice and easy and vice free in the wet and damp.
i have yet to try a 'plated' lsd in this car. from what ive heard and read, they are probably the ultimate in absolute traction as they lock the drive axle solid, but they are clunky at paddock speeds and the ramps and plates do wear so the 'tightness' settings do change through its life.
for me the quaife is all things to all tracks, i cant be arsed to change diff styles if it rains ;-)
Craig
I swapped the original plate type Diff in the Griff for an ATB last winter. On the road it is has been completely vice free( well apart from throwing all the oil out of the breather but that is a separate point) . The reason for fitting it was to improve performance on hillclimbs. With the original one the less loaded rear simply spun uselessly producing lots of tyre smoke out of corners until the car was completely settled. Provided both the wheels are actually on the ground the ATB allows you to get on the power a lot earlier and appears seamless in the way it allocates the drive. As said by others if you actually have a driven wheel off the ground all the power goes to that one which can give some odd handling when it lands again. This has only really been a problem for me on really tight corners where the camber compleatly unloads one rear, like for example the final hairpin at Wiscombe.
One thing that I have found is the car now tramps badly in the wet. No amount of changing the springs or damper settings will control it and nothing else changed at the rear when swapping the diff. I have begun to think that it is actually the load transferring alternately to left and then right rather than something suspension wise loading and releasing. Interestingly I was talking to a 911 driver who had found exactly the same problem with his new ATB. The only thing left to try is replacing the Diff carrier bushes but there is no trace at all of the problem in the dry.
On balance it was a good decision and I have been quicker this year due to getting better drive out of corners, it has required a change in driving style because previously I could plant the throttle and the unloaded rear wheel spun harmlessly, now the ATB actually gets some power on the road and there is more tendency to oversteer so more right foot control is required.
One thing that I have found is the car now tramps badly in the wet. No amount of changing the springs or damper settings will control it and nothing else changed at the rear when swapping the diff. I have begun to think that it is actually the load transferring alternately to left and then right rather than something suspension wise loading and releasing. Interestingly I was talking to a 911 driver who had found exactly the same problem with his new ATB. The only thing left to try is replacing the Diff carrier bushes but there is no trace at all of the problem in the dry.
On balance it was a good decision and I have been quicker this year due to getting better drive out of corners, it has required a change in driving style because previously I could plant the throttle and the unloaded rear wheel spun harmlessly, now the ATB actually gets some power on the road and there is more tendency to oversteer so more right foot control is required.
Steve-V8S
wow, pretty well exactly the same syptoms as ive had! ive experienced the tramp and assumed that the majority was the semi-trailing arms design issues. altering the angle of the trailing arms chassis pick-up point relative to the axle centre line helped a lot, this winter is solid or semi solid diff carrier bushes to see if that cures it.
i need to get the wheel speed sensors hooked up to the logger which would prove the ATB 'cyclical' grip/unloading on a hard launch.
i get the problem, wet or dry (quite violent in the dry with slicks tbh)
wow, pretty well exactly the same syptoms as ive had! ive experienced the tramp and assumed that the majority was the semi-trailing arms design issues. altering the angle of the trailing arms chassis pick-up point relative to the axle centre line helped a lot, this winter is solid or semi solid diff carrier bushes to see if that cures it.
i need to get the wheel speed sensors hooked up to the logger which would prove the ATB 'cyclical' grip/unloading on a hard launch.
i get the problem, wet or dry (quite violent in the dry with slicks tbh)
Edited by CNHSS1 on Friday 17th October 10:17
Interesting that you also get it in the dry, what car are you running ?. I have no trace of it at all either with list 1b list 1a or slicks in the dry. If it is, as I suspect due to the way the diff works when there is next to no grip at either wheel I guess it would be dependent on the amount of grip that is available and the power level. After hearing that that 911 chap had the same symptom I asked around the paddock looking for other comparable cars with an ATB but could only find front wheel drive cars with them fitted, none of which found the problem. Despite the logon name I am running a Griff so don’t have the trailing arm suspension which was the reason for selling the V8s. With that I suffered the opposite problem of tramping off the line in the dry but not in the wet which in the end I put down to the trailing arm set-up.
steve-V8s said:
Interesting that you also get it in the dry, what car are you running ?.
Scimitar SS1 Turbo ModProd
i can get tramp in the wet if theres enough grip, but given the nature of launching a turbo'd car you need to be fairly aggresive so usually grunt overcomes traction anyway.
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