Options for those who want overdrive on their TJ (42RLE vs AW4 vs ?)

[mrblaine]

Ah so my flaw is in the statement:

"I agree with @machoheadgames the same load is not being put on a 5.13 tooth as a 4.10 tooth as the mechanical advantage (distance from the ring/pinion contact gear to the pinion center axis) is less but it doesn't fully make up for a the aforementioned weaknesses of a smaller pinion in a dynamic system."

The smaller pinion is a non issue. The ultimate failure would be at the shaft diameter. Since we rarely see shafts twisted in half, it is a non issue. FYI- dynamic is redundant. We will always assume the system is in use.

The point is that it does make up for it, at least enough to not be of any concern. You have given me much to think about. I actually work for an OEM transmission/differential manufacturer. You have given me much to discuss with the engineering team this week. I suspect they will confirm exactly what you have pointed out and educate me further on the FEA and validation backing it up.

Thanks for administering the exam, will study harder next time.

I have the benefit of a very smart engineer who used to work for Boeing. He laid out a bunch of this stuff on Jeep Forum back in the day and only a few of us are left to carry it forward.

Most of the mythology centers around observation and intepreting that incorrectly as causation while staring at the obvious and different but more correct answer.

 

[Negreac]

The smaller pinion is a non issue. The ultimate failure would be at the shaft diameter. Since we rarely see shafts twisted in half, it is a non issue. FYI- dynamic is redundant. We will always assume the system is in use.

I have the benefit of a very smart engineer who used to work for Boeing. He laid out a bunch of this stuff on Jeep Forum back in the day and only a few of us are left to carry it forward.

Most of the mythology centers around observation and intepreting that incorrectly as causation while staring at the obvious and different but more correct answer.

Ah yeah, I probably should have clarified when I used the term Dynamic. I meant it more in the sense of considering heat and stress cycles over time as opposed to a static model where you are only considering the forces on the system at a single point in time.

 

[mrblaine]

Ah yeah, I probably should have clarified when I used the term Dynamic. I meant it more in the sense of considering heat and stress cycles over time as opposed to a static model where you are only considering the forces on the system at a single point in time.

I will relate a very cute story about causation and observation tomorrow. Out of time tonight. Down under diff builder, smart folks who missed the obvious.

 

[mrblaine]

On POR, in Gen 4x4, a new diff builder as in starting from scratch building highly specialized IFS and IRS differentials for race cars, started a post asking if the group knew of any gear sets that were not made as crappy as the ones they had been buying as samples, cutting in half, and then testing for hardnes. They were very sad and made a big point over how cheaply made they all were since the tooth faces always tested out very nicely in the hardness but then the cores or insides of the teeth were softer. They seemed very offended and saddened by the current state of gear making and were wanting to know if anyone knew of a company that made a gear that was through hardened so they could buy some samples and test them.

The only part that surprised me was how long it took for the "group" to explain what they were seeing was not a cheap or an inferior way to build a gear, it was the preferred method to use case hardening alloys so you could create a high hardness wear surface over a more ductile core which resisted higher loads, they didn't break as easily and were not brittle.

They took a proven method and interpreted it to be inferior because in their mind, harder was better and stronger and they could prove it with their testing.

They are still in business, they make some very cool stuff and they appear to have cleared up their confusion some. Like most things, the mistakes we make are not knowing enough to ask the right question.

 

[Wildman]

The "NEW" kid on the block is the 8HP70 and there are a lot of adapter kits for putting it behind other than stock engines... Now you just need to find someone who will make one for the 4.0... There are already standalone wiring harnesses since the TCM is built into the transmission. You have to use a 4x4 transmission so you have to have the TCM flashed to a Challenger or Charger programing then you get the tap shift option.

That 4.71 1st gear would sure be nice off-road... I've got one sitting in my garage waiting to go behind my Hemi sometime next year... The only "BAD" thing I've read at this point is that since it's all electronically controlled doing a 1st to Rev isn't as quick as one mechanically controlled.


The gear ratios for the ZF 8HP70 transmission are: 1st: 4.714, 2nd: 3.143, 3rd: 2.106, 4th: 1.667, 5th: 1.285, 6th: 1.000, 7th: 0.839, 8th: 0.667, and Reverse: 3.317. These ratios provide a wide spread for fuel efficiency, with a strong 4.714:1 ratio in first gear for quick acceleration and closely spaced gears from 5th to 8th for smoother shifts.

Here is a detailed breakdown of the ZF 8HP70 gear ratios:

• 1st Gear: 4.714
• 2nd Gear: 3.143
• 3rd Gear: 2.106
  4th Gear: 1.667
  5th Gear: 1.285
  6th Gear: 1.000
  7th Gear: 0.839
  8th Gear: 0.667
  Reverse: 3.31
  
  
  
  
  
  
  

 

[Rickyd]

The "NEW" kid on the block is the 8HP70 and there are a lot of adapter kits for putting it behind other than stock engines... Now you just need to find someone who will make one for the 4.0... There are already standalone wiring harnesses since the TCM is built into the transmission. You have to use a 4x4 transmission so you have to have the TCM flashed to a Challenger or Charger programing then you get the tap shift option.

That 4.71 1st gear would sure be nice off-road... I've got one sitting in my garage waiting to go behind my Hemi sometime next year... The only "BAD" thing I've read at this point is that since it's all electronically controlled doing a 1st to Rev isn't as quick as one mechanically controlled.


The gear ratios for the ZF 8HP70 transmission are: 1st: 4.714, 2nd: 3.143, 3rd: 2.106, 4th: 1.667, 5th: 1.285, 6th: 1.000, 7th: 0.839, 8th: 0.667, and Reverse: 3.317. These ratios provide a wide spread for fuel efficiency, with a strong 4.714:1 ratio in first gear for quick acceleration and closely spaced gears from 5th to 8th for smoother shifts.

Here is a detailed breakdown of the ZF 8HP70 gear ratios:

• 1st Gear: 4.714
• 2nd Gear: 3.143
• 3rd Gear: 2.106
  4th Gear: 1.667
  5th Gear: 1.285
  6th Gear: 1.000
  7th Gear: 0.839
  8th Gear: 0.667
  Reverse: 3.31
  
  
  
  
  
  

What is the length? You can't exactly push the straight 6 forward to compensate like with a v8

 

[Wildman]

What is the length? You can't exactly push the straight 6 forward to compensate like with a v8

You'd have to go back & look in my thread or search online... I forget right now. But I know it's close to the 545RFE length... You've asked this at least twice now. And I can tell you there really isn't any pushing a V-8 forward in these swaps... Matter of fact I pushed the Hemi as far back as I could.

I'm finding 23.75" for a length... But I can't find if that is bellhousing to rear flange or not....


Edit: Hemi 5.7 is 29.625" long & what I could for the 4.0 is 32.2" long..

 

[Negreac]

Seems like it might fit, hard to say from pictures alone.

 

[Negreac]

8HP70 behind a Hemi in a TJ. Looks to be about a 5"-6" stretch but don't know if that is necessary for this trans.

 

[Wildman]

8HP70 behind a Hemi in a TJ

Yep we've talked about it a lot in the Hemi swap thread... Like I said I've got one sitting in my garage. Just need the time & money to swap it into my TJ.

The standalone wiring harness is $1240 currently & available from Sound German. https://www.soundgermanautomotive.com/pcs/
I've still got to gather the needed parts to install it behind my Hemi.

If you could get a adapter for the bellhousing & then a torque plate for the torque converter to match up to the 4.0 it might be a good swap.

There are some different shifter options too depending on how you want to go.

 

[Negreac]

Is anyone aware of a refence list of transmission lengths from bell housing to T-case mounting surface? I have a 32RH and AW4 in my garage I can measure but not successfully found definitive lengths for the 42RLE, AX15, NV1500 or NSG370.

Would also be good if someone had any reference for T-Case lengths. I know it can be difficult to measure cause they have varying outputs. Also have an NP231 and NP242 sitting in my garage but would like to find the NP241OR & Dana 300 (could probably measure my buddies CJ). Found a good video measuring the Atlas and Behemoth Colossus so have those already.

Found it surprisingly difficult when trying to compare overall lengths of different combinations. Would think this would have been collected somewhere already since none of this stuff is new and is fairly important for drivetrain selection.

 

[Wildman]

I've got just short of 28" with the 4x4 adapter on my 8HP70. And from what I've been able to find out a 8HP75 is 2-3" longer.

This is the Challenger shifter. No shifter cable needed. It's all electronic.

Now figure out the adapter between the engine & bellhousing and then a flex plate for the torque converter and you're done.

This is what AI says about the 42RLE: The 42RLE transmission is approximately 33 inches (2.75 feet) long,

 

[Wildman]

Grant had the adapter plate mad for the AW4 to VW engine so I don't see why you couldn't do the same here. Or find a company that wants to ramp up the tooling.

 

[Negreac]

Grant had the adapter plate mad for the AW4 to VW engine so I don't see why you couldn't do the same here. Or find a company that wants to ramp up the tooling.

Yes I believe @Jezza also made one for his 6L80E, granted I think that was a one off just for himself.

 

[Wildman]

Yes I believe @Jezza also made one for his 6L80E, granted I think that was a one off just for himself.

My point is that it could be done. And there are companies making adapters for the 8HP70 like I said before already. For LS swaps & Nissan and Toyota and other engines. So it's not rocket science.

 

[Negreac]

So I added the 8HP70 and the 6L80E to the chart. With those high 0.667 OD gears even with 5.38s you would only be pushing 2400rpm at 70mph granted that is with true 35" tires about a 150rpm bump for true 33". I assume if you had some power adders to the 4.0L that would be less of an issue. That mid 50-60s crawl ratio even with a 2.72 T-case is nice though. Could even keep the less bulky/shorter (SSYE) NP231 and get a better ratio than the NV241OR on any of the transmissions.

 

[Wildman]

So I added the 8HP70 and the 6L80E to the chart. With those high 0.667 OD gears even with 5.38s you would only be pushing 2400rpm at 70mph granted that is with true 35" tires about a 150rpm bump for true 33". I assume if you had some power adders to the 4.0L that would be less of an issue. That mid 50-60s crawl ratio even with a 2.72 T-case is nice though. Could even keep the less bulky/shorter (SSYE) NP231 and get a better ratio than the NV241OR on any of the transmissions.

View attachment 643364

I think based on the discussions I've read about the 8HP70 and how well it shifts that even with that O/D it'd kickdown to keep it in the powerband. Also the 8HP70 is supposed to eat up less power than other auto transmissions. As Todd said in that video where he'd said it felt like it'd gained 20HP.
This is one reason I want to wait until next year to swap the 8HP70 into my TJ. I want to get some more seat time with the 545RFE so I can have a better feel for what I think once I do the 8HP70 swap.

 

[RustyAutoholicGuy]

I just got back from a work trip and I’m playing catch up on this thread but wanted to give my two cents on everything very quickly.

The AW4 is a great cheap automatic and you can solve all the problems with it over heating by swapping in a later valve body out of a Toyota Tacoma A340 automatic that has a solenoid to control line pressure. Yes that means you need a CompuShift controller to control the transmission but that basically fixes any issues you might have with the AW4 along with getting a ton of tuning options as well. It also has the benefit of bolting directly to the 4.0l engine and all the transfer cases that came in a TJ as well. Understand the CompuShift is the biggest expense here.

I’ve gone down the rabbit hole of the 8h70 along with other transmission and they are the “new kid” on the block but they have several drawbacks as well. Length, weight, and cooling complexity as well. The 8hp70 needs it’s own dedicated transmission cooler, it can not be integrated into the factory radiator. Also for all the controls that “work” with the 8hp70, they need WAY more information from the CANBUS to operate, percentage of torque, percentage of load, and several other data points that I can’t remember off the top of my head. I’m not saying it’s not possible but the length, weight and all the information required from the engine ECU to run it properly is the main concern. I looked at bolting the 8hp70 to my BEW TDI and the TDI ECU did not have the correct parameters required to operate the 8hp70. Just something to keep in mind.

You can be into the AW4 with a parts A340 for the valve body and the CompuShift controller for under 2K. For setting up the transmission in the CompuShift software you’ll need to say you are running a Toyota A343 transmission which was the same gearing as the AW4 but the software to handle line pressure.

I have not had a single over heating issue with my AW4 since I put in the Toyota A340 valve body where line pressure is controlled by the CompuShift ECU and the only cooling I’m running currently is the factory TJ Wrangler radiator. In terms of space, length, and easy of install, the AW4 is the transmission of choice from me. Also you can get the XJ Cherokee shifter for it and it will factory bolt into the TJ center console as well.

I’ll go back and re-read the entire thread to see if I missed anything.

Thanks
Grant

 

[jeepguy03]

The AW4 is a tough transmission. It has funky shift points, and runs hot, but I'd definitely choose it over the 42RLE. I ran my AW4 in my lifted XJ with 33s with just a cooler, never complained. Several others in my group ran them in XJs and completely thrashed them, minimal maintenance, ran them through water, etc, typical teenager with a cheap Jeep stuff. Never had one fail, and we tried, one guy punctured his transmission pan and didn't realize it until it stopped moving forward. Filled it back up and that Jeep still drove fine until it was totaled by someone who ran a red light a few years later.

Slap a good cooler on it, change the fluid appropriately and you'll be good with an AW4.

 

[jeepguy03]

The "NEW" kid on the block is the 8HP70 and there are a lot of adapter kits for putting it behind other than stock engines... Now you just need to find someone who will make one for the 4.0... There are already standalone wiring harnesses since the TCM is built into the transmission. You have to use a 4x4 transmission so you have to have the TCM flashed to a Challenger or Charger programing then you get the tap shift option.

That 4.71 1st gear would sure be nice off-road... I've got one sitting in my garage waiting to go behind my Hemi sometime next year... The only "BAD" thing I've read at this point is that since it's all electronically controlled doing a 1st to Rev isn't as quick as one mechanically controlled.


The gear ratios for the ZF 8HP70 transmission are: 1st: 4.714, 2nd: 3.143, 3rd: 2.106, 4th: 1.667, 5th: 1.285, 6th: 1.000, 7th: 0.839, 8th: 0.667, and Reverse: 3.317. These ratios provide a wide spread for fuel efficiency, with a strong 4.714:1 ratio in first gear for quick acceleration and closely spaced gears from 5th to 8th for smoother shifts.

Here is a detailed breakdown of the ZF 8HP70 gear ratios:

• 1st Gear: 4.714
• 2nd Gear: 3.143
• 3rd Gear: 2.106
  4th Gear: 1.667
  5th Gear: 1.285
  6th Gear: 1.000
  7th Gear: 0.839
  8th Gear: 0.667
  Reverse: 3.31
  
  
  
  
  
  

An 8HP70 would be a cool swap behind a 4.0 for sure. I love the one behind my Hemi, definitely an upgrade in the Grand Cherokee over the 6 speed auto it replaced. Tows much better with the 8 speed. I have friends with tuned turbo BMWs and even on track days their ZF8 transmissions hold up quite well.