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800+ WHP Scat Build Transmission Question

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Well, I've been doing research on a few different builds for my Scat and went from wanting an NA build with high compression to looking into a SC Scat that would be able to run faster than a demon from a rolling start. Parts are pretty easy to understand with the engine upgrades and related topics, but I've hit a learning barrier when it comes to the Transmission options. I want to keep driving this car comfortably at car shows and out to grab grocery's. I've already worked out the rest of the car, but how can I have a manual transmission with that much balls and still keep the ride somewhat comfortable with a tr-6060 and dual clutch upgrade?

I know the gear ratios will definitely not work with the Scat Trans and 3.90 diff being:
1st 2.97 >too short for 800+HP Even if I upgrade the diff.
2nd 2.10 >also short as hell
3rd 1.46
4th 1.00
5th 0.74
6th 0.50 > This seems perfect for high HP

Compared to the hellcat trans with 3.70 diff:
1st 2.26 >This seems much better for 800+
2nd 1.58
3rd 1.19
4th 1.00
5th 0.77
6th 0.63

Anyways, I'm kind of nerdy with technical data, so don't be afraid to get technical with your responses and opinions. I'm just trying to make this thing work for what I want it to do which would be a 800WHP build that will be very drivable in the city or highway.
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Discussion Starter · #3 ·
Go over to hc.org and look at all the blown up tranny’s (there’s a bunch of pics of blown up transmissions too : )

I think a 4L60 auto is the answer. Even at only 800 wheel
🤦‍♂️ Not even close to what I asked.
 

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Discussion Starter · #4 ·
It's a tough question... I better just call MMX and talk with an expert and I'll relay the information back to this thread.
 

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SC Scat that would be able to run faster than a demon from a rolling start.

how can I have a manual transmission with that much balls and still keep the ride somewhat comfortable with a tr-6060 and dual clutch upgrade?
IMO
Not going to happen

It's possible But you're starting a bottomless money pit. Money/parts/labor it's just not worth it.

Good luck if you decide to take that journey.
 

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a SC Scat that would be able to run faster than a demon from a rolling start.
Rolling start is the key and driven properly the stock Hellcat/Viper 2.26 M6 should hold up.

The clutch for all Challengers is already a dual disc and the Hellcat clutch is 258mm compared to the Scat Pack 240mm.

For the rear I'd stay with the Scat Pack 3.90 ratio, with the .63 overdrive at 75 mph you're still only about 2200 rpm.

Not sure if the Hellcat M6 driveshaft is different (stronger) than Scat Pack so I'd check into that.

For halfshafts, go with the Redeye 41-spline shafts 77072535AB.

So this is the minimum that I think you could get away with provided no standing start launches are in the plan.


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Discussion Starter · #7 ·
IMO
Not going to happen

It's possible But you're starting a bottomless money pit. Money/parts/labor it's just not worth it.

Good luck if you decide to take that journey.
Money is just tool to get it. A nice ride on with a proper manual is worth the cost imo. The dealership didn't have a brand new manual hellcat or I would have went that route. Actually they told me they stpped making them. Although, I could find a used one, now I just want to build it and have a Scat sleeper. I was very surprised to see how many folks want to race you based on driving a Scat... I mean, I drive like I stole it, but it's just funny when every bmw m3 4 and 5 think we are racing and I'm just normally driving fast. Lol, imagine the look on their faces when rip past with that supercharger whining. Then I tell a bold face lie and say, "it's stock bro. Your expensive car is just slow."

Rolling start is the key and driven properly the stock Hellcat/Viper 2.26 M6 should hold up.

The clutch for all Challengers is already a dual disc and the Hellcat clutch is 258mm compared to the Scat Pack 240mm.

For the rear I'd stay with the Scat Pack 3.90 ratio, with the .63 overdrive at 75 mph you're still only about 2200 rpm.

Not sure if the Hellcat M6 driveshaft is different (stronger) than Scat Pack so I'd check into that.

For halfshafts, go with the Redeye 41-spline shafts 77072535AB.

So this is the minimum that I think you could get away with provided no standing start launches are in the plan.


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Awesome info, thank you!

I was thinking of going the red eye rear end route, so I'll probably take your advice. I didn't think the Scat diff would be able to handle that hp, but if it will, I'd just keep that.

I was going to use an aftermarket street triple or dual clutch, but honestly if the hellcat clutch can handle that power, I would rather go that route, because of how smooth it will be compared to the cost of the triple. The aftermarket would probably out last my Trans, too which would make me super nervous. I'd rather have a clutch just on the borderline, and fail but save my tranny than a clutch rated for 1000tq when my Trans is only rated for 800ish.

I have 315 rear tires, but I keep them all weather, so I don't think I'll ever have the grip to take a demon on the track, not sure about the hellcat Trans making it out alive, but if it can take the numbers, I'd go that way all day! With the all weather tires, do you still think launching will break something?

Rolling start is the key and driven properly the stock Hellcat/Viper 2.26 M6 should hold up.

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This guy states he is using a hellcat tr6060 with 850 HP. Those look like street tires and he's launching all day. It's looking promising !
 

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Ur trying to build an NA Scatpack stick shift thats gonna beat a Demon from a Roll? No one keeps their Demon stock bro. I think u need to stop drinking and come back to planet Earth!

This is as technical as I can get. The COST would be prohibitive! You have a better chance of seeing Elvis at Burger King today then making that ever happen!

So u think an NA MMX kit is gonna give u 800 whp? The experts from MMX are gonna say "Its nice to dream kid but come back to reality."
 

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it's just funny when every bmw m3 4 and 5 think we are racing and I'm just normally driving fast.
I know exactly what you're talking about:ROFLMAO::LOL::ROFLMAO: and to also include Toyotas, F150 pick ups, the list is just ridiculous, it is very comical how when I drive by people all of a sudden they turned into a race car driver:ROFLMAO::LOL:

do you still think launching will break something?
launching when you have good traction is when you break things.
 

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I'd keep the really tall 6th gear.

The 0.63 in the HC means at 75-80mph you're still turning 2200 RPM, which means only 20MPG.
If it were 0.50 or even lower like 0.45 you could be turning down in the lower 1k RPM, which with the torque these engines have they are perfectly happy to do all day long, and now you'd see hwy MPG closer to the A8. (the HC has as much torque down at 1200 RPM as the 392 does at peak...)

Unless you plan on doing 1-mile 200mph runway pulls, no one needs such a short 6th gear, I always drop the gear to pass anyways, so don't care if 6th overdrive is too high to accelerate well--I'd much prefer it.
 

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The .63 gearset is stronger than the .50, that's why they used it on Viper and Hellcat. Same with the 2.26, this makes the trans much stronger than the 2.97 I guess if you're getting one built you could mix some ratios around but it's gonna cost big.


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Discussion Starter · #14 ·
Ur trying to build an NA Scatpack stick shift thats gonna beat a Demon from a Roll? No one keeps their Demon stock bro. I think u need to stop drinking and come back to planet Earth!
You might want to stop drinking and learn to read. lol

I know exactly what you're talking about:ROFLMAO::LOL::ROFLMAO: and to also include Toyotas, F150 pick ups, the list is just ridiculous, it is very comical how when I drive by people all of a sudden turned into a race car driver:ROFLMAO::LOL:

launching when you have good traction is when you break things.
Lol, Oh Sorry! I forgot to mention the F-150s!

I plan on not launching this thing other than to show off and spin tires and goofing off around corners. Also I don't really plan on putting anything but all-weather tires on it. Excellent advice, however, I'll take it.

The .63 gearset is stronger than the .50, that's why they used it on Viper and Hellcat. Same with the 2.26, this makes the trans much stronger than the 2.97 I guess if you're getting one built you could mix some ratios around but it's gonna cost big.


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Having one built might be the option I'm looking at. I guess I could always break mine and then have it rebuilt stronger... lol.

Actually, if I use the first three from the Hellcat and keep the last three gears from the Scat, It would be Ideal for my purposes. I found the this PDF on the tremec website. https://www.tremec.com/anexos/TREMEC_TR-6060_1017.pdf If you look at option F it has the pretty much the exact gears we are discussing.

I wonder if there is a way of upgrading the Transmission mainshaft? That's where the torque compacity comes from anyway right?

Unless you plan on doing 1-mile 200mph runway pulls, no one needs such a short 6th gear, I always drop the gear to pass anyways, so don't care if 6th overdrive is too high to accelerate well--I'd much prefer it.
Great points! I 100% agree. I'm not going to drag this thing anyways. It's just for highway cruising and messing about.
 

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Great points! I 100% agree. I'm not going to drag this thing anyways. It's just for highway cruising and messing about.
1/4 mile drag doesn't touch 6th gear... so even with a nice tall 6th for better hwy mpg you could still have a great weekend drag strip 1/4 miler car--and get much better gas mileage getting to and from the track... dunno what Dodge was thinking on that 6th gear. Might've helped with the gas guzzler tax and obviate the silly skip-shift too.
 

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I found the this PDF on the tremec website. https://www.tremec.com/anexos/TREMEC_TR-6060_1017.pdf If you look at option F it has the pretty much the exact gears we are discussing.
Yeah that looks good, I might try this trans before a built aftermarket one. Probably will need a better clutch and have no idea what to run, nothing will drive as smoothly as the stock clutch and that's usually the issue with aftermarkets.




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Discussion Starter · #17 ·
Yeah that looks good, I might try this trans before a built aftermarket one. Probably will need a better clutch and have no idea what to run, nothing will drive as smoothly as the stock clutch and that's usually the issue with aftermarkets.
Do you know a good place I could check pricing for this Tremec?
 

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Discussion Starter · #18 ·
Ok, After some back and forth with the a couple of guys at Tremec I learned that my Scat Trans is good to for a lot more ft lbs than I originally thought, surprisingly. Predictably, it's mostly the main shaft that determines that. The only thing is, it's geared so low, It won't be fun to drive with all that extra beef. Thankfully you can upgrade the first 3 gears to what ever specs you want. If what you want is 2.66 or 2.26 first gears lol. I was also told by a rep at Tremec that the best way to get the gears to take more Torque is to have the materials heat treated and hardened, but there are only a few shops in the US that do that kind of thing. One in Pittsburg, PA was recommended. So, my next step is to do some investigating and see what they have to offer.

Also, something interesting I didn't know is the "TR-6060" series manual trans is only available from the OEM for purchase. If I wanted something different from Tremec aftermarket I would have to use the magnum series for upgrading.
 
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