Summarize the 6MT Situation For Me

[LKG]

Sounds like there's a great "Crime Watch" story in there somewhere.... but, like you, I would certainly buy another MT. I just can't figure out why Jeep refuses to let me option out my dream Jeep; 2-dr, 392 Hemi, MT with 4.88s:

Credit: I "lifted" this from some other forum member who initially posted it. In a nutshell it IS my dream Jeep.

Right... Nobody died and I got a great upgrade so it had a happy ending, for me at least.
I think a 2 door with a 392 would be terrifying, but a good terrifying

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[Sportacus]

It seems like the issue is too many people who think they know how to drive stick buy manual wranglers

 

[LSJKU]

Okay, but you aren't going to have this weak ass manual transmission behind V8 Power and expect it to survive. Give me an NVG4500 and let me row tractor gears, I'll be happy as hell.

Yes, you're correct, sir! Would really love that granny gear in the NV4500, but I decided on the Tremec T-56 (TR-6060) a long time ago. It's an all around better manual for everything BUT rock crawling. Plus, the NV4500 takes more mod's to make it work.

But... if somebody wants to donate an NV4500 to the cause, I wouldn't turn it down. How awesome would that be, rowing truck gears and crawling around in a 5:1 or 6:1 granny gear with the 4:1 Rock-Trac? Then again, I'm assuming the Rock-trac will work with either. I would need adapters, a different shaft or, most likely, a different transfer case altogether. I haven't dug that deep into it, just recalling the LS/16L80 swap in my JKU. I had to go with an aftermarket NP transfer case for that swap.

And then there are the axle considerations with all that torque on tap with no converter to manage it... oh man, it get's really deep very fast. That's why Stellantis should give us the opportunity to order what we want; get it right from the factory to begin with.

 

[LSJKU]

In reality, it may be too much to think I can actually pull off a 392/Tremec swap. I would likely just go with the 8HP70 because I could source it all as one item from the junk yard and not worry about building an SRT/Tremec Frankenjeep. But i sure would miss the manual. That's one reason I did not go with the 392 from the factory. That and I wanted a 2-door Jeep, not a 4-door. Se la vie!

 

[bllprk]

How long have you had your CF clutch and how do you compare it to the factory one?

I have had 3. I love it when it works.

1. Purchased my 2018 JLU with 44,000 miles. Threw on 33's right away. Tried to teach my 15 year old a MT and he just couldn't make it work. The clutch was on or off.

2. Re-gear to 5.13's with 35's. He still really struggled to figure it out. 64k Miles

3. CF's second try at a JL Clutch - CFII - External Slave - 65k miles. It worked amazing. Totally different than stock. Feathering great. Moab Trip. My son figured it out instantly. Didn't pay much attention to cleaning the input shaft spline / probably added too much grease.

4. With 10k Miles on it, clutch started acting up. Hard to get it into 1st and reverse. Accidentally filled the bell housing with mud and destroyed the rest of the clutch.

5. Cleaned out the clutch, and while waiting for a new clutch, put the old one back together. Clutch worked again and shifted great. (cleaned input spline)

6. A week later installed a new CF clutch (same one) but with Internal Slave. Very small amount of grease on input shaft. LOVE the feeling of the internal. Easy press. Easy bleed. Used this setup for 30k miles. Started to not like 1st. Started to get stuck in gear when I started the engine.

7. At 105,000 replaced the clutch. This time CF said no lube on the spline. Its pre-lubed with a dry lube. Super cleaned the spline. Love the performance again. Sitting at 5000 miles on new clutch. Hoping for the best

 

[jeepingib]

Yes, you're correct, sir! Would really love that granny gear in the NV4500, but I decided on the Tremec T-56 (TR-6060) a long time ago. It's an all around better manual for everything BUT rock crawling. Plus, the NV4500 takes more mod's to make it work.

But... if somebody wants to donate an NV4500 to the cause, I wouldn't turn it down. How awesome would that be, rowing truck gears and crawling around in a 5:1 or 6:1 granny gear with the 4:1 Rock-Trac? Then again, I'm assuming the Rock-trac will work with either. I would need adapters, a different shaft or, most likely, a different transfer case altogether. I haven't dug that deep into it, just recalling the LS/16L80 swap in my JKU. I had to go with an aftermarket NP transfer case for that swap.

And then there are the axle considerations with all that torque on tap with no converter to manage it... oh man, it get's really deep very fast. That's why Stellantis should give us the opportunity to order what we want; get it right from the factory to begin with.

Well the 4500 was optioned behind some early Hemi blocks in Ram 2500 trucks before they stopped offering them. And if we are dreaming might as well go with an atlas case or a 3 spd stak box. Or whoever is making them these days.

 

[onepoundjeep]

love the info in this thread. I hadnt had MT is 15 yrs and was itching for one. after test driving it I knew I had to have it. I think removing the spring or the Act softer spring definitely helps.

all are correct on issues, but I still dont care (1st world problems), I would never pick AT. I got 33s and 3.45 gearing, its a dog, but its also a jeep not a sports car.

I debate regearing, I wanna test drive rubicon to see the difference it would make.

if i could get a centerforce clutch with guarenteed no issues I think I would do that if anything tho.

 

[azwjowner]

I debate regearing, I wanna test drive rubicon to see the difference it would make.

I have 4.56 and 32s and it's transformative.

Also, I'm glad to read all the comments in this thread about how awful it is to learn the clutch. My JL is my first manual car -- I had it shipped from Mark Dodge and then taught myself how to drive around my neighborhood from YouTube tutorials. I had an awful time and stalled about 100 times, but glad to know I'm not uniquely stupid.

 

[gato]

It's really simple.

Choice A: The absolute best automatic on the planet - ZF8 with 8 gears to keep you always in the power band.

Choice B: Possibly the worst manual implementation on the US market today. Defanging SW recalls, exploding clutch plates setting vehicles on fire, ridiculously bad gearing made worse the second you even think about putting bigger tires on.

 

[alphawolff]

I have had 3. I love it when it works.

1. Purchased my 2018 JLU with 44,000 miles. Threw on 33's right away. Tried to teach my 15 year old a MT and he just couldn't make it work. The clutch was on or off.

2. Re-gear to 5.13's with 35's. He still really struggled to figure it out. 64k Miles

3. CF's second try at a JL Clutch - CFII - External Slave - 65k miles. It worked amazing. Totally different than stock. Feathering great. Moab Trip. My son figured it out instantly. Didn't pay much attention to cleaning the input shaft spline / probably added too much grease.

4. With 10k Miles on it, clutch started acting up. Hard to get it into 1st and reverse. Accidentally filled the bell housing with mud and destroyed the rest of the clutch.

5. Cleaned out the clutch, and while waiting for a new clutch, put the old one back together. Clutch worked again and shifted great. (cleaned input spline)

6. A week later installed a new CF clutch (same one) but with Internal Slave. Very small amount of grease on input shaft. LOVE the feeling of the internal. Easy press. Easy bleed. Used this setup for 30k miles. Started to not like 1st. Started to get stuck in gear when I started the engine.

7. At 105,000 replaced the clutch. This time CF said no lube on the spline. Its pre-lubed with a dry lube. Super cleaned the spline. Love the performance again. Sitting at 5000 miles on new clutch. Hoping for the best

Lol, I had to do a double take. 3 clutches in 100k miles is crazy. Talk about a love hate relationship

 

[Ol’ Timey Manual SWB Guy]

It's really simple.

Choice A: The absolute best automatic…

Choice B: Possibly the worst manual…

https://www.jlwranglerforums.com/fo...-better-than-8-speed-auto.151075/post-3129073

 

[yokramer]

After reading through here it seems that the JL manual owners are just masochists.

 

[Vinman]

It boggles my mind how Jeep cannot make a reliable manual transmission with the correct gear ratios. You’d think after 80 years they would have it all figured out.

 

[Remorseless]

 

[LSJKU]

Well the 4500 was optioned behind some early Hemi blocks in Ram 2500 trucks before they stopped offering them. And if we are dreaming might as well go with an atlas case or a 3 spd stak box. Or whoever is making them these days.

Since we're dreaming, I'll finish my "old" ideas. But I did a deep dive late last night into what it would take to do the swap correctly, and now understand why an aftermarket SRT/Tremec swap is not feasible.

TLDR: Bottom line, an SRT/Tremec swap is physically doable, but to do it right, you're gonna spend at least $60,000 to $70,000, if not way more. And what I found leads me to believe it's the primary reason Jeep will never offer the factory 392 backed up by a manual tranny.

Once again Dusty, you nailed it. An Atlas II would be a great choice with the Tremec coming out of a donor Corvette or Shelby/GT350/GT500, or even the NV4500 out of an early Ram 2500/3500. The clutch assembly could also come out of an early Ram 2500/3500, but it requires a bell housing that would adapt to the Hemi and still have room for the Ram clutch/modified flywheel assy (most likely leading to trans tunnel mod's). That's all doable with adapters and brackets coming from 3rd parties, and help from a local fab shop, just really, really complicated.

What makes me wince and have nightmares is the PCM and electronics. My intentions relied on a basic misconception, that the SRT PCM would be plug-n-play. Not so. The chassis-side wiring harnesses between the JL Rubi 3.6L and the 4-door 392 are totally different. That was an eye-opener. While MOPAR does supply a PCM with the SRT crate that will work with the swap and overcome most problems, like the donor vehicle security and the immobilizer, it still has to be integrated with the JL chassis wiring harness for all to work nicely together. Then you get into the tuning issues. Sure, you can flash the SRT PCM with a manual trans tune to get rid of the TCM, but what do you do with all the other electronic bits like MDS on the modern Hemi, and so on? That has to be a tuners worst nightmare.

When I did the LS/16L80 swap into my JKU, that's precisely the point where I failed and learned new limits. At the end of the day I had to give it to MoTech and let them complete the build. And I still spent well over $30,000 (back in 2014/2015) to finish the ill-thought out project, with two PCM's installed, one for the driveline side and one for the chassis side. That nightmare is still floating around in my memory.

And I haven't even touched on the associated costs. I'm already installing RCV's and chromo's in my D44/M220 axles, but that's nowhere near enough to prevent the torque available from the manual tranny from snapping those axles in certain situations. You gotta go 1-tons (Currie), and absorb all the costs associated with that swap. The costs get waaay outta hand very quickly.

@jeepingib I want to thank you for the impetus to do a deep dive on the SRT/Tremec swap. While doable, it's nowhere near the plug-n-play option I so casually referred to on this forum. I had no idea a SRT/manual tranny would be so much more complicated than an SRT/8HP70 swap. And I now understand why Stellantis will never offer the option of a 392 backed by a manual in the JL line; Jeep relies on the auto's converter to manage the 392's high torque thru the entire driveline. The prices others paid for the 392FE would not even touch the price point it would take to cram a manual behind the 392.

Please excuse me while I retreat to the corner and sulk a while. The dream of a 392 in my JL is not totally dead, but it's not coming with a manual. To get back to the OP's topic at hand, thank goodness I am really happy with the 3.6L MT, with Brad's tune flashed.

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