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Discussion Starter · #1 ·
I’m looking for opinions & recommendations on how to plan my manual transmission build project. The car is a stock 2018 Hellcat Widebody M6. I plan to keep the power at stock level. I do some drag racing, but definitely not a track-junkie.

Main reason I want to build a new transmission: Change the gear 1-3 ratios to match the 392 cars. Secondary reason: replace clutch “while I’m in there” because the factory clutch probably doesn’t have much life left. My last trip to the drag strip produced some strong clutch odors.

I want to buy a used transmission and rebuild it myself in my garage. I have the tools and experience from building LS race engines, so I’m pretty sure I can learn how to rebuild a manual transmission. I also want to keep my stock take-out manual transmission on the shelf as-is, so I can always return the car to 100% stock in the future if I wanted to.

Main question: Which option is better for me?
  1. Buy a used Hellcat transmission and change gears 1-3.
  2. Buy a used 392 transmission and change gears 5-6 (4th gear is the same ratio in both cars). Are the input/output shafts the same in both cars?
In either case, I’m not sure what other mods would be required to ensure the rebuilt transmission can handle the stock Hellcat torque output. Any recommendations there?

I've read this whole thread about 5 times, not sure what some of the terms mean like "magnum shafts" and "triple cone synchros" M6 transmission upgrade

Also, I found this link. Is this accurate for our TR-6060 transmission? http://juchems.com/ServiceManuals/viewfile2ffb.pdf

Thanks for reading.
 

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by the time you buy a used hellcat tr6060 your not far from just getting a built one i would think. While I dont know how to build them, I was doing some research as well for a possible swap down the road. What I am seeing is that internals are not going to be the same between a 6.4 and 6.2 car tranny. I think thats what I was reading. Bearings, main shaft, gears, etc.

Anyway, looking forward to see what you find out.
 

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The stock 392 Transmission is rated for 500 ft lb, the Hellcat is rated for 650 ft lb. The Hellcat Transmission uses a Transmission Cooler.
 

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I installed a 2.98 first, 2.10 second, 1.43 third 850 ft lb rated TR6060 Tranzilla in the fall. With 830 wheel Really brought the animal out in the car, track closed by the time I was ready to test it out. Fitted 17” 315 DR’s and anxiously waiting on spring. But street testing has shown a dramatic increase in launch G’s, .95-1.05 verse .7-.8 on the street and consistent 11.4 street 1/4’s on 315/35-20 Nitto NT05R DR’s so so far it’s looking promising.
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I installed a 2.98 first, 2.10 second, 1.43 third 850 ft lb rated TR6060 Tranzilla in the fall. With 830 wheel Really brought the animal out in the car, track closed by the time I was ready to test it out. Fitted 17” 315 DR’s and anxiously waiting on spring. But street testing has shown a dramatic increase in launch G’s, .95-1.05 verse .7-.8 on the street and consistent 11.4 street 1/4’s on 315/35-20 Nitto NT05R DR’s so so far it’s looking promising. View attachment 548666 View attachment 548667 View attachment 548668
How much did the Tranzilla cost? Do they sell outright or modify your existing Transmission?
 

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I bought a complete unit from a member here on one of the Hellcat forums but from talking to Rockland Standard Gear (RSG) about it it’s about 3500-5 k to mod a core (yours) depending on upgrades wanted. The 2.98 first with 3.73 rear almost equals the automatic’s final drive ratio with a 2.62 rear so launching on a taller tire should be much better and be a more equal playing field trying to keep up with the autos on launch. I’m hoping for 1.5 or better 60 ft times.
 

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I have the 3.90 rear in mine, I also bought the BBG Clutch from the same guy you got the Bell housing from. I am thinking the 2.66 1st and .50 6th.
 

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I’d love to try the 2.66 first with my 3.73, the 2.98 and 3.73 would be as deep as I’d go, it’s already brutal trying to control wheel spin, I’m hoping at the track I can dead hook and break a seat loose lol. I’ve been thinking about having my original tranny converted to a 2.66 Tranzilla and see which I like better but that’s a bit of out lay to “just try out” lol With a 3.90 rear I agree 2.66 would be the gear for you as well, 2.98 3.90 together be too deep with the low end torque these cars make. Agree on the .50 6th
 

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Discussion Starter · #10 ·
Good stuff, do you know specifically what was upgraded inside the transmission for the 2.98 gear to handle the Hellcat torque?

What clutch are you running? Do you recommend it for street driving?

I installed a 2.98 first, 2.10 second, 1.43 third 850 ft lb rated TR6060 Tranzilla in the fall. With 830 wheel Really brought the animal out in the car, track closed by the time I was ready to test it out. Fitted 17” 315 DR’s and anxiously waiting on spring. But street testing has shown a dramatic increase in launch G’s, .95-1.05 verse .7-.8 on the street and consistent 11.4 street 1/4’s on 315/35-20 Nitto NT05R DR’s so so far it’s looking promising. View attachment 548666 View attachment 548667 View attachment 548668
 

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All gears replaced 1-4 and 6 made from 4340, 5th from 9310. Carbon fiber synchros , all new bearings, different shafts, a pretty long list, in a nut shel your case and shift forks get reused most everything else is replaced with better stuff.

Yes, I like it better even on the street. There’s no stalling it, period, you let the clutch out and it’s going somewhere even without stepping on the gas. Spinning the tires on command in first or second only takes a small blip on the throttle, third depends on rpm your at. Street max G’s up from .65-.75 to .9-1.05. If your not planning on taller slicks for track I’d go with the 2.66 first unit.
 

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Discussion Starter · #13 ·
Do you have a build sheet you can post? Thanks.

All gears replaced 1-4 and 6 made from 4340, 5th from 9310. Carbon fiber synchros , all new bearings, different shafts, a pretty long list, in a nut shel your case and shift forks get reused most everything else is replaced with better stuff.

Yes, I like it better even on the street. There’s no stalling it, period, you let the clutch out and it’s going somewhere even without stepping on the gas. Spinning the tires on command in first or second only takes a small blip on the throttle, third depends on rpm your at. Street max G’s up from .65-.75 to .9-1.05. If your not planning on taller slicks for track I’d go with the 2.66 first unit.
 

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No, I asked RSG for the BOM but they said it’s for internal use only but George the gentleman who manages that Dept read off to me what was done to the unit I have from their BOM. Weird but it’s what it was and all I could get even trying other routes.
 

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Discussion Starter · #16 ·
If your not planning on taller slicks for track I’d go with the 2.66 first unit.
So you're recommending #3 on this list, for mostly street driving?

1-2 gear shift points, 6,000 RPM, with 305/35/20 tire:

3.70 axle, 2.26 1st gear: 60.6 mph (stock M6 setup)
3.90 axle, 2.26 1st gear: 57.5 mph
3.70 axle, 2.66 1st gear: 51.5 mph
3.90 axle, 2.66 1st gear: 48.9 mph
3.70 axle, 2.98 1st gear: 46.0 mph
3.90 axle, 2.98 1st gear: 43.6 mph
2.62 axle, 4.71 1st gear: 41.1 mph (stock A8 setup)
 
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Went to the track second week of March, they opened for one day, glad I went. 2.98 first, 3.70 rear, 315/50-17 MT Street R’s first on only time out on them netted a 1.51 60’ and 10.7- 10.9 134-135 mph runs pass after pass. Added 50 hp and some BMR goodies in the rear since so hoping for the predicted mid 10’s or lower next time out when ever the damn tracks open up again.

 

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Ok, finally a track day, busy as hell, waited 3 hours to get a turn and unfortunately only got 1 turn, got there at 8 am, 2 pm I got disgusted and left, NEVER saw this Little hole in the wall track so busy before. But one pass was all I needed for what I’ve been working towards for the last 2 years, a 9 second pass. Was only by .002 seconds but it starts with a 9 and that’s all that counts :) Was all in the launch, 315/50-17’s hooked like on fly paper and the 2.98 first just ripped, hit second perfect and from there down the track I knew it was going to be a good run.
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