Summarize the 6MT Situation For Me

[LSJKU]

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

That's a very good thread I had never read before, or more likely, forgot about.

As our aging senator John Cornyn is famous for saying "I'm just like you, I'll take two!"

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[LKG]

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.

I say keep the NV4500 and wedge a Cummins in there, no more mods to bolt up the tranny. In fact, all you need is a Gen 2 Dodge donor, motor, tranny, T-Case, axels, you're set! I expect to see a YouTube series on the swap

 

[jeepingib]

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.

I think a small body lift would allow the room for the 4500 bellhousing to be close enough to work. It still seems like the most feasible way to get a Hemi 6 spd to work in the Jeep.

 

[LKG]

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.

I had a 22 Sport altitude for 4 whole months before it was totaled but was able to upgarde to a Rubicon (thanks to post pandemic used car values). The 4.10's are night and day better than the 3.45's IMO. However if not for the "incident" I'm certain I'd be running 33's and stock gearing and still loving every minute of it. The test drive is a great idea, asuming you can find a manual.

 

[2nd 392]

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.

Jeeez, kinda makes you opine for the good ol” days. Do the needed drivetrain, cooling, frame, fuel system upgrades, get the adapter, install the Chevy-Muncie, connect fuel and 12 V , done.

 

[drpericak]

I've had 4 Wranglers. 2013, 16,19,23. All 6 speed 4 door Rubis. I put roughly 90K on each one and have never had an issue with the transmissions. I also never let them do the software update fix thingy either.

 

[Steve104]

I did not have the recall done and have had no issues.

 

[LSJKU]

Jeeez, kinda makes you opine for the good ol” days. Do the needed drivetrain, cooling, frame, fuel system upgrades, get the adapter, install the Chevy-Muncie, connect fuel and 12 V , done.

Sure does! Oh, the good ole' days....

The first Jeep I bought, a well-worn '74 CJ-5, I dropped in a 401 AMC and did it all myself, except boxing the frame and having the motor B&B'd. Second one, the 2012 LSJKU caused severe pain when I got to integrating the electrical and power control management. Had to have someone else finish it. Now, after some deep research, I don't even want to take on an SRT swap. "Technological advances" have burst my bubble.

From here on out I'll stick to the mod's I can do myself, but mostly concentrate on enjoying the JL in it's current incarnation. It's still awesomely fun to drive and puts a smile on my face every time.

 

[2nd 392]

Sure does! Oh, the good ole' days....

The first Jeep I bought, a well-worn '74 CJ-5, I dropped in a 401 AMC and did it all myself, except boxing the frame and having the motor B&B'd. Second one, the 2012 LSJKU caused severe pain when I got to integrating the electrical and power control management. Had to have someone else finish it. Now, after some deep research, I don't even want to take on an SRT swap. "Technological advances" have burst my bubble.

From here on out I'll stick to the mod's I can do myself, but mostly concentrate on enjoying the JL in it's current incarnation. It's still awesomely fun to drive and puts a smile on my face every time.

Yep, 1 SBF (difficult, too long) , and 3 Chevy swaps at Dad’s garage. Including mine, an L-79 Muncie from a wrecked C-2, also a Big Shaft Wagon D-18 with Warn OD, in my 63 MD. The only mistake was just upgrading the axles, but damn, what the rear end shop wanted for a cut down 9” was so much I have memory block and can’t recall the number.

 

[dac219.9]

Is Ford

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.

Is Bronco’s manual transmission better than the Wrangler’s manual transmission?

 

[jbcrane]

In brief summary what is the exact issue with the manual trans in the JL? Is it all of them? What about the JK?

Brief Summary:
They had some (pretty big) problems earlier, but they've since sorted them out. Don't know about the JK.

A Little More History:
When mine (m.y. '21) went in for the 19A replacement about this time last year it had only once given me an overheat warning - totally my fault, stuck in the snow and not knowing at the time to disable traction control. For reference, that happened the first winter following buying him new in April '21.

I'd been hearing/reading the horror stories (not disputing them...) so finally last year at about 45K miles and fearing the worst, decided to 'get ahead of it' and get the replacement over with. A lot of folks went aftermarket (Centerforce, ACT, some South Bend, etc.). I wanted to keep the factory drive train for plenty of reasons so took the free clutch from the dealer.

I took him to Brandon CDJR in Loveland, CO. After several conversations with several dealership service writers, they inspired the most confidence. It took about 2 days start to finish, and they offered (I didn't ask for) a loaner. I made it clear I wanted any and all associated procedures completed as well (like the relearn, etc.) before picking it up. When I asked to see the original factory clutch at pick up, the tech pulled it out and said it looked brand-new, like it had never been used.

All that to say I don't know why some have had such horrible problems while others such as myself have not. It does/did seem a small percentage of people had problems, but those that did had really big problems. Mine has been perfect, despite my early ignorance and subsequent abuse.

It might be worth noting that same first winter I re-geared to 4.88 after adding lift & tires (315's). It felt like the stock 3.45's would not help the clutch situation one bit with the additional strain getting the heavier Jeep in motion. So the clutch had a little help from the re-gear early in its life. (I'm convinced that 4.88's paired with the 6-MT and 315's/35's are a perfect setup, esp. for the 4-door).

Since then I haven't had a single problem and honestly, have forgotten all about the earlier issues. I just don't think about or worry about it any more. And FWIW, it seems the number of clutch-related threads has fallen off sharply over the past year.

If you want to drive an auto, drive an auto. If you want to drive a manual, drive a manual. You're either willing to put up with it's unique qualities or you're not. But no tranny is trouble-free. As for me and my house, I'd never consider an automatic transmission in the Jeep.

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