Gen III Hemi Swap into TJ Reference Guide & Swap Info

[Wildman]

The 8HP70 isn't a NEEDED thing for me it just with all the other things I'm dealing with not having the shifter cable would be a added plus but I'm also sure I can get this shifter cable figured out. The transmission I have now is shifting fine & working but if I find a deal & then can find the other parts needed for a deal I might do it.

 

[NashvilleTJ]

The 8HP70 isn't a NEEDED thing for me it just with all the other things I'm dealing with not having the shifter cable would be a added plus but I'm also sure I can get this shifter cable figured out. The transmission I have now is shifting fine & working but if I find a deal & then can find the other parts needed for a deal I might do it.

Nothing at all wrong with doing projects for the challenge of doing it. Full electronic shift would be cool.

 

[Wildman]

Nothing at all wrong with doing projects for the challenge of doing it. Full electronic shift would be cool.

I'd like to get all the kinks worked out of the Jeep first before I pull it apart again... But I don't mind gathering the parts so I have them here when I'm ready.

 

[Hammer_c]

Well I know I won't be the first but I might be the first active member to try it out... The hardest part for me is the shifter but I'm sure with a little time and measuring I could figure out a mount for it. Or I can do the aftermarket shifter... But I'll deal with that if I pick up this used transmission and really start into it.

Not sure how the OEM shifter would mount with the Genright console but really all you need is a flat surface with enough surface area to attach the four bolts.

The stock console turned out to be way easier than I originally thought. I just traced out a piece of aluminum to cover the 5 speed hole, installed nut inserts, and even reused the boot.

 

[Wildman]

Not sure how the OEM shifter would mount with the Genright console but really all you need is a flat surface with enough surface area to attach the four bolts.

The stock console turned out to be way easier than I originally thought. I just traced out a piece of aluminum to cover the 5 speed hole, installed nut inserts, and even reused the boot.

View attachment 581351

View attachment 581352

Is yours running/driving yet?

I'm sure it would just take being creative and figuring out a mounting plate/stand for the shifter. I need to do a little more research and see if I can find anything on the difference between the stock shifter and one of the aftermarket shifters.

 

[Hammer_c]

Is yours running/driving yet?

I'm sure it would just take being creative and figuring out a mounting plate/stand for the shifter. I need to do a little more research and see if I can find anything on the difference between the stock shifter and one of the aftermarket shifters.

It is running and driving. I got on the road about a year ago and have around 5,000 miles on the build.

 

[lowell66dart]

What muffler's are folks using. I have a MBRP cat back muffler and tailpipe and had a custom Y pipe with no cats built. The MBRP really sounded nice with the 4.0 but it doesn't play nice with the HEMI. I have GC cast manifolds. It sounds nice at start-up and idle and wide open throttle but anywhere else is horrible. Sounds like a bad exhaust leak. Something has to change next week.

 

[NashvilleTJ]

What muffler's are folks using. I have a MBRP cat back muffler and tailpipe and had a custom Y pipe with no cats built. The MBRP really sounded nice with the 4.0 but it doesn't play nice with the HEMI. I have GC cast manifolds. It sounds nice at start-up and idle and wide open throttle but anywhere else is horrible. Sounds like a bad exhaust leak. Something has to change next week.

I run this Flowmaster HP 2. Very nice, controlled sound. Not loud at all, not obnoxious, and no drone. It does scream nicely when you smash the loud pedal. I'm very happy with it.

The shape also fits the tight space well.

https://www.summitracing.com/parts/flo-12518304

 

[lowell66dart]

I run this Flowmaster HP 2. Very nice, controlled sound. Not loud at all, not obnoxious, and no drone. It does scream nicely when you smash the loud pedal. I'm very happy with it.

The shape also fits the tight space well.

https://www.summitracing.com/parts/flo-12518304

Thanks. Looks interesting

 

[Daubie3]

What muffler's are folks using. I have a MBRP cat back muffler and tailpipe and had a custom Y pipe with no cats built. The MBRP really sounded nice with the 4.0 but it doesn't play nice with the HEMI. I have GC cast manifolds. It sounds nice at start-up and idle and wide open throttle but anywhere else is horrible. Sounds like a bad exhaust leak. Something has to change next week.

Some interesting information I found on Summit's website about mufflers..

 

[Wildman]

I did something a little different for mine. I couldn't find one muffler that I really liked so I used two to make one.

The inside of the resonator is twisted which I think helps swirl the exhaust.

Then into a two chamber short muffler.

The Forest Service requires a chambered type muffler which acts like a spark arrester up here.

I cut the ends off and welded the two mufflers together and IMO it makes a really nice note. The one thing that I'm surprised by was that the Hemi doesn't have the same exhaust note as the Magnum V-8. The overall length is about 22" long.

 

[Apparition]

I did something a little different for mine. I couldn't find one muffler that I really liked so I used two to make one.

View attachment 583642

The inside of the resonator is twisted which I think helps swirl the exhaust.

View attachment 583643

Then into a two chamber short muffler.

View attachment 583644

The Forest Service requires a chambered type muffler which acts like a spark arrester up here.

View attachment 583645

I cut the ends off and welded the two mufflers together and IMO it makes a really nice note. The one thing that I'm surprised by was that the Hemi doesn't have the same exhaust note as the Magnum V-8. The overall length is about 22" long.

View attachment 583646

Need to setup the camera for a drive by to see what everyone else hears.

 

[Wildman]

Need to setup the camera for a drive by to see what everyone else hears.

Yep, it's on my list of things to do...

 

[lowell66dart]

Didn't have much going on this morning so I removed the muffler without too much trouble. I could only see into the inlet. It's got chambers and cutouts to grab the exhaust flow. I saw a one inch hole down in it but no daylight on beyond it. I didn't have anything to lose so I took a two foot half inch extension and went through the hole and punched through the plate beyond it. Just trying to change the flow somehow. Bolted it back up and I got rid of abour half of the rattle but it's still gotta go.

I found a few videos of the Flowmaster Nashville mentioned and I like it alot. Going to call my muffler guy Monday and get a price to install.

My 2.5 tailpipe is pretty tight passing between the fuel tank and shock. I would have to move the shock to fit three inch pipe. It doesn't look like the Flowmaster can be bought with anything bigger that 2.5 in and out also. My engine is bone stock and with the exhaust as short as it is on a TJ I don't think were giving up much flowwise.

 

[NashvilleTJ]

View attachment 583636

Some interesting information I found on Summit's website about mufflers..

I definitely give up a few ponies with my exhaust setup. I run 2.5" all the way back. In hindsight, I wish I had done a 3", but that's a challenge given space constraints. I'm always giving thought to redoing it. Perhaps one day.

Here is a nice example of the sound:

 

[Wildman]

Didn't have much going on this morning so I removed the muffler without too much trouble. I could only see into the inlet. It's got chambers and cutouts to grab the exhaust flow. I saw a one inch hole down in it but no daylight on beyond it. I didn't have anything to lose so I took a two foot half inch extension and went through the hole and punched through the plate beyond it. Just trying to change the flow somehow. Bolted it back up and I got rid of abour half of the rattle but it's still gotta go.

I found a few videos of the Flowmaster Nashville mentioned and I like it alot. Going to call my muffler guy Monday and get a price to install.

My 2.5 tailpipe is pretty tight passing between the fuel tank and shock. I would have to move the shock to fit three inch pipe. It doesn't look like the Flowmaster can be bought with anything bigger that 2.5 in and out also. My engine is bone stock and with the exhaust as short as it is on a TJ I don't think were giving up much flowwise.

I can't speak to the Hemi but on the Magnum V-8's the guys who kept their stock TJ exhaust & then later swapped to a 3" exhaust noticed a marked difference power by doing so. If it was mine I'd seriously look at swapping to a 3" exhaust.

I definitely give up a few ponies with my exhaust setup. I run 2.5" all the way back. In hindsight, I wish I had done a 3", but that's a challenge given space constraints. I'm always giving thought to redoing it. Perhaps one day.

Here is a nice example of the sound:

I guess I hadn't paid attention to this as I'd always thought you'd done a 3" exhaust... And YES fitting it is a huge PITA...

 

[Wildman]

Just some playing around with GrimmJeeper's gear calculator.

This is with the 06 & newer 545 gearing. And my STaK's 3.05 & 5.44 low ranges.

I started looking into this because I'd been talking with Sound German Automotive in Bellevue, WA and he'd indicated that the 8HP70 might not play well with my current gearing. But I reached out to folks on FB and the JeepSpeed group which are mainly JK's & JL's but they're running comparable tires & gearing. And they all are responding with "GO FOR IT" and "It's A GAME CHANGER" and all say they don't have any issues with the 8HP70 and the lower gearing.

 

[lowell66dart]

Just some playing around with GrimmJeeper's gear calculator.

This is with the 06 & newer 545 gearing. And my STaK's 3.05 & 5.44 low ranges.

View attachment 584208


I started looking into this because I'd been talking with Sound German Automotive in Bellevue, WA and he'd indicated that the 8HP70 might not play well with my current gearing. But I reached out to folks on FB and the JeepSpeed group which are mainly JK's & JL's but they're running comparable tires & gearing. And they all are responding with "GO FOR IT" and "It's A GAME CHANGER" and all say they don't have any issues with the 8HP70 and the lower gearing.

Did Sound German give you any reasons why they didn’t think it was a good idea?

 

[Wildman]

Did Sound German give you any reasons why they didn’t think it was a good idea?

He said that the lower gearing would mess with the 8HP TCM but I don't think he's taking into account for the tire size. He said that the 8HP wants to see approximately 2K RPM's a 70 MPH which is what the RPM's would be with my current setup.

The thing is that you are starting with a 4.7 1st gear ratio. So a lot of the stuff you have done ends up at best being overkill. But on top of that the factory tcm does start doing some weird stuff if the total tire/gear size ratio is way outside the box. You want to gear for something around the under 2k mark in 8th at around 65mph. Something in that range works pretty well. The 8 speed has the same overdrive as the 545 so that should tell you where the box is.

The 03-06 545 had the 0.067 O/D in 5th where the 07 & newer 545 is 0.050 O/D 5th

 

[lowell66dart]

He said that the lower gearing would mess with the 8HP TCM but I don't think he's taking into account for the tire size. He said that the 8HP wants to see approximately 2K RPM's a 70 MPH which is what the RPM's would be with my current setup.



View attachment 584231

The 03-06 545 had the 0.067 O/D in 5th where the 07 & newer 545 is 0.050 O/D 5th

Thanks for the explanation. My tranny is an 05 and I was not aware of a ratio change.

I have 4.56’s with a metric 35 inch tire and I am pretty happy with the combo but I don’t do anything close to what some of you do with your rigs.

Just an FYI since we are talking about overdrive. My recent harness from Hotwire does enable OD via the factory OD off button, just no light.