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Transfer Case Experiences

 
Old Jan 20, 2015, 10:26 AM
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Transfer Case Experiences

Background: My car is not a drag car. I primarily use it for SCCA autox, but one form of the sport is Pro Solo. Pro Solo involves a drag launch off a tree followed by an autox course.

When I started building my car, I had a stock tcase for the first Pro Solo of 2012. With two drivers, I was afraid it was going to grenade on me, so we found a fresh Shep stage 1 tcase with a quaife front diff. I put that in the car and ran the rest of 2012, 2013, and part of 2014 on it before I got a really loud whine under load. The ring and pinion were not happy with each other. I pulled it out and put in an equivalent spare that had some abuse on it (from my co-drivers old BSP car). That tcase finished the 2014 season and is still in the car.

Request:
I'm looking for real world experience with various transfer case build options. I know everyone has their favorite vendor (TRE, Shep, etc.) and a lot of reviews are based on customer experience and perceived product performance. I'm interested in who bought an XYZ built tcase and broke it. What was done to the tcase, and how many launches did it survive? How much power was the car making, 60 ft times, etc.?

In the Solo world, I know the street prepared guys treat these as a wear item, but they also cannot use anything but OEM ring and pinion and case bolts. My class (street mod) can do whatever we want. I am about to send in the whining stage 1 tcase for a rebuild, and am thinking about going full retard overkill in hopes that I can stop worrying about it every time we run a Pro (or at least try to ). Full retard = $$ obviously, so what have other's experience been? Anyone break a top build from Shep or TRE? Anyone put a ton of abuse on a less than full retard build and have it survive?


Some data:
My oem internal, reshimmed, 10mm case bolt, quaife front diff shep "stage 1" saw:
212 total launches
108 launches on asphalt
104 launches on concrete

Our launches are usually in the 1.6xx range. I think once I cut a 1.59x, but the 60ft distance was suspect at that event (everybody was having slightly better 60fts).
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Old Jan 22, 2015, 06:28 AM
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Purchased my car used with around 95k miles on stock OEM Tcase. It now has around 106K after 3 years of ownership. It was previously used as a autoX car with prob lots of events on it. My transmission is stock refreshed but my front and rear diffs are stock OEM original parts.
Launches are as followed
500whp=30 launches
600whp= 10 launches
700whp= 12 launches
Currently 789whp= 4 launches

best of 1.51 60ft

I don't beat or abuse the car and the only time it even sees boost is the track.
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Old Jan 23, 2015, 06:53 AM
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So a stock unit will not outright fail at higher whp levels if launched properly... good news. There is a lot to be said for launch technique, because improper launches will break these tcases at stock power levels. Wheel hop on corner exit also can do a number on them
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Old Jan 23, 2015, 07:30 AM
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I just recently moved to the ebrake method of preloading the drive train. I hear that is the best way to take some of the stress off. Each and every diff is going to be different but if you have owned the car for a long time and take care of it, you should be confident in its ability to stay healthy.
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Old Jan 23, 2015, 09:17 AM
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I use the ebrake method as well, often by necessity because the Pro Solo starts are not level.

I was hoping for more folks to chime in with their experiences. I wonder if most people simply do not put enough launches on their cars to see the carnage we do in Pro Solo. One weekend is easily 30-40 launches with two drivers.
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Old Jan 26, 2015, 07:33 AM
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I think most just believe the hype and go out and purchase a built diff because that's what everyone else does
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Old Jan 26, 2015, 07:42 PM
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100k mile stock rs tcase. Over 70 launches. Slicks 1.48 consistent 60 fts. No problems. Beat **** out of it. I'll rebuild once something fails. Untill than I don't worry about it. 600whp. Going to be around 800whp this year and gna keep going till something gives.
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Old Jan 29, 2015, 01:17 AM
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^^^ CROWN are you on 2step if so what is it set at? do you also have a twin disc? When I get my car back I will have a little more power 650-700 in that range. no slicks just toyo r888s
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Old Jan 29, 2015, 10:07 AM
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Just 2 step no launch control. set at 6100rpm. would build about 13psi on the fp black. had exedy twin that decided to melt. i'd invest in slicks if going to do a lot of track racing at the strip. be a lot easier on your drivetrain, that and if you have a good enough clutch to preload it helps a lot to.
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Old Jan 29, 2015, 05:28 PM
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thanks, just woundering tho, wouldnt slicks make it harder on the drivetrain because it would want to hook instead of spin? I don't know I'm just asking.
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Old Jan 30, 2015, 08:22 AM
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Slicks will spin a bit but cut down the chances of wheel hop. Wheel hop is what kills the drive train.
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Old Jan 30, 2015, 11:16 AM
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Originally Posted by aquaMan219 View Post
thanks, just woundering tho, wouldnt slicks make it harder on the drivetrain because it would want to hook instead of spin? I don't know I'm just asking.


Drag slicks, no. The cushy sidewall prevents wheel hop.


Road race slicks, if you launch poorly can cause wheel hop and brake things..
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Old Feb 1, 2015, 08:16 PM
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I have info for your analysis, only... I've never broke a tcase yet.

First: Shep built tcase, wavetrac LSD, ACD
2nd: Stage 1 (forget who "built" it) RS LSD, non-ACD

The ACD tcase saw many, many launches with huge torque. All on hoho DR's, and some street tires. Also saw a few days of autox on way too much power. I killed 3 transmissions while I had this tcase. Tcase never had an issue, sold, still working.

Non-ACD has seen much less launches, and most have been on slicks. Killed another trans and tcase is still going.


I honestly don't see a tcase being a weak point on our cars, unless you're the unlucky guy with one that had a defect/assembly error. Or you don't maintain them. I change fluids CONSTANTLY. Maybe other forms of racing they see other stresses in turns, or with axes at weird angles...
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Old Feb 2, 2015, 05:50 AM
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What fluid have you been using in the tcase?

Maybe it is a combination of the tires and quantity of launches, but it is not uncommon for an SP or SM evo to break a tcase at a Pro Solo. A lot of folks carry spares for that reason (myself included). I have also gotten wheel hop on corner exit (the "evo hop") that requires getting out of the throttle to settle the car before it breaks something.
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Old Feb 2, 2015, 05:55 AM
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Here is a typical launch for reference.

2014 SCCA Wilmington Pro Solo - JSC Speed SM Evo:
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