I currently have a built bottom end S366 IX MR with a completely stock 6 speed, transfer case, and rear diff. The car makes around 530whp right now on low boost, but I'd like to safely turn it up in the near future. I do have a spare Shep stage 1 5-speed laying around, but my biggest concern is the T-Case and Rear Diff. For power levels around 700 - 800whp, what do I really NEED to build for the drivetrain to be safe at those power levels? I know all the usual players, TRE, Shep, Jack's, etc. and what they offer. But are any of the upgrades they offer worth it or necessary? For example, do I really need the Stage 2 along with Wavetrac LSD and Isotropic Finishing that Shep offers? Do I need the full race prepped rear diff options that TRE offers? Etc.

As an FYI, the car is not my daily. It's a purely weekend/toy car so I'm not worried about "driveability" issues if that's a thing. Occasional visits to the drag strip, so would be nice to be able to launch this thing without being afraid of grenading the entire drivetrain.

 

From my understanding with the shep stage 2 tcase is the upgraded ring and pinion(Billet, I think) which is suppose to take a beating...

 

if your gonna drag it... shep, jacks or tre... with wavetrac

 

I am currently trying to decide exactly which options I am going to add to my drivetrain build. Hopefully those with first hand experience can speak up, but as far as I know:

Power levels alone are not the biggest factor, it's the type of use, drive style/shifting, LAUNCHING and low end torque that are more significant.

Ask yourself how much you can afford to break your drivetrain, and enjoy removing and repairing/replacing it later, when you found out the hard way whether your "need" it built.

Lots of Evos have run very quick times even with an open front diff and been driven on the street with high power levels. If the power is from a large turbo, high in the RPM range, and it is shifted nicely and patiently, it could operate fine for a long time. If you are like me, and care much more about as getting as much torque as possible as early in the RPM as possible to huge sticky tires, and are going to autocross (maintain and fluctuate low to high RPM in lower gears with high tq.) and lap it on track (long sessions=heat), I consider investing in a performance build to withstand it reliably a "need."

"what you need" in terms of the options available has less to do with "will the car put x # down on the dyno, withstand some street driving/pulls, and some drag racing, for who knows how long" vs. how cool and quiet it will operate, how smooth it will shift under hard use and at high RPM, how much abuse it can withstand, and how long it might last under the same circumstances. How reliable, strong, wil probably depend greatly depending on type of use and how hard, long, hot, and possibly imperfectly your drive it (abuse it).

Your IX 6 speed is less desir\able and durable than would be ideal for most types of racing. Gear ratios. Your stock LSD is better than nothing and has gone quick/fast but not as good as Wavetrac or Quaife.

Example: front LSD. Do you "NEED" it? No, but you don't "need" 700whp either. You want it, and you want it to be as reliable as possible, and a front LSD will help you use the 700whp better, and help prevent an open diff from destroying your tcase as easily. If you have an open front diff, IMO, yes, you absolutely need it for anything besides highway pulls from a roll.

Rear LSD, you would be remiss and missing out on one of the most effective and fun mods to your Evo to skip it IMO. One of the first mods I did to mine and worth every penny. It's reliable, AND FUN.

A built drivetrain is expensive, and nobody seems to be nearly as eager to dump money into it vs. parts that make more than enough power to destroy it, until their car is down for possibly the race season or year and then they have to do it, almost always at greater expense than just doing it preventatively. $2500-5500 sounds like a lot until you have trailered (or driven, bigger consequence then) a car to an event far away, paid a hefty race day fee, used the gas, tires, maybe hotel, etc. and then have to pack it all up and head home, missing a lot or the rest the season because you destroyed your tcase/trans.

Final drive, re-gearing. Nobody else can really tell you if you need it. That's up to you and your intended use, tire diameter, etc. spend the time to figure it out and or spend the extra ~$850.

Cryo, micropolishing, WPC, etc., see above.

The offerings from "the three" drivetrain builders are all a bit different so it's not as a simple as "you need level 1/street from vendor A, or level 3 "race" build from vendor B."

All that being said, both the tcase and trans seem to be "fine", I already have a Quaife and will continue to use it after a rebuild, I am most likely getting a "performance"/"race" level build, 4.1 FD, will be spending around $5k, and I am only planning on 450/450-500/500>. So at the power and torque levels you say you intend to use, I would.

If anyone has more first hand experience driving performance built with and without addition gear/synchro treatments, please share, thanks.

 

Thanks Hokiruu, that's a very thoughtful and well laid out response. What I'm hearing (and already assumed) is build it for any possible outcome. I guess I was really looking to see if any of the added options that the various vendor offers are more of a gimmick and not actually needed. As far as the best vendor, from many years of observing it appears that TRE is the best but can take a very long time, but is worth it in the long run. Who will you be going with?

 

Sorry for the slow reply, for some reason I didn't get or missed the notification. I have been trying like hell to go with TRE, since months basically. Like every day or 2, to no avail. The last parts for my long block assembly are trickling in next week, so I need to get something going very soon. Unless something happens with TRE, I will probably be using Jacks. I'd love to have a TRE built car and have been waiting, but I'd rather have a car built by whoever that RUNS, as long as it's worth the money spent. I am still not 100% sure exactly which treatments I will spring for, but it's going to be a hefty expense either way.