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Old 08-22-2012, 12:12 AM   #1
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More Speeds In A Manual Tranny Than In Auto ???

Why is it that the manual transmission of a TJ has either 5 or 6 speeds, whereas a TJ automatic transmission has only either 3 or 4 speeds?
(You'd think that they would have made the trannies similar, with the same amount of gearing, no matter if YOU are shifting or if the TRANNY is shifting for you.)

Does this make the TJ automatic transmission work harder than the manual transmission at highway speeds, due to the fact that since the auto trans only has 3 or 4 speeds?

Does this make the engine of the auto trans rev at higher RPMs than the manual transmission?

Also, I am particularly interested in the 4.0L engine.
Which automatic transmission would be paired up with the 4.0L?

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Old 08-22-2012, 12:42 AM   #2
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This is really weird. I just now got done explaining all this to my 10 year old son. I log on and someone else is asking the same question.


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Originally Posted by vertical horizons View Post
Why is it that the manual transmission of a TJ has either 5 or 6 speeds, whereas a TJ automatic transmission has only either 3 or 4 speeds?
There are two reasons I can think of.

1. The auto transmission has a torque converter and doesn't need as low of a first gear to get the vehicle going.

2. Auto transmissions are much more complicated than manual transmissions. It's much easier and more cost effective to add gears to a manual transmission.


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Originally Posted by vertical horizons View Post
Does this make the TJ automatic transmission work harder than the manual transmission at highway speeds, due to the fact that since the auto trans only has 3 or 4 speeds?

Does this make the engine of the auto trans rev at higher RPMs than the manual transmission?
Not if they both have similar overdrive ratios, i.e. .75:1. At highway speeds the torque converter locks up and doesn't allow any slippage. The 42RLE auto has 4 speeds with overdrive. The 32rh only has 3 speeds and doesn't have overdrive, so yes, the Jeep will rev a lot higher on the freeway with this transmission.

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Originally Posted by vertical horizons View Post
Which automatic transmission would be paired up with the 4.0L?
From 1997 to 2002 they have the 32rh 3 speed (no overdrive).

2003 to 2006 has the 42RLE 4 speed with overdrive.

Many people have swapped their manual transmissions for the AW4. The AW4 is a good four speed automatic transmission from the Cherokee.

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Old 08-22-2012, 11:35 AM   #3
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Quote:
Originally Posted by Border Dave View Post
... Many people have swapped their manual transmissions for the AW4. The AW4 is a good four speed automatic transmission from the Cherokee.
Thanks for the input.
I like that idea.
But now that brings up more questions ...
  • Is the AW4 tranny a 4 speed with OD, or just a 4 speed?
  • The 32rh is for certain year TJs, and the 42rle is for other certain year Tjs. Which TJ years would the AW4 mount up to?
  • Are any mounting bracket changes required?
  • What about the shifting lever inside of the vehicle? Can that remain in place? (I like the shifter that comes with the TJ.)
  • Is there a reason why someone would swap out and go with the AW4, instead of swapping out with either the 32rh or the 42rle?
Sorry for all of the questions. But now you've opened a can of worms. And I'm interested.
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Old 08-22-2012, 11:41 AM   #4
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I just googled the AW4 transmission.

Less than great reviews -

The Jeep AW4 Transmissions - Novak Conversions

Not entirely bad, but they said that " ...They have a tendency to generate excessive amounts of heat, and are known for unnecessarily consuming more engine power than some other automatics. The shift points in the AW4 feel odd, and the spotty engagment of the lockup torque converter is idiosyncratic.
But, it is a decent transmission, and if kept cool and maintained, it can offer good service within its range... "

Opinions, anyone?
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Old 08-22-2012, 11:45 AM   #5
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Quote:
Originally Posted by vertical horizons View Post
Thanks for the input.
I like that idea.
But now that brings up more questions ...
  • Is the AW4 tranny a 4 speed with OD, or just a 4 speed?
  • The 32rh is for certain year TJs, and the 42rle is for other certain year Tjs. Which TJ years would the AW4 mount up to?
  • Are any mounting bracket changes required?
  • What about the shifting lever inside of the vehicle? Can that remain in place? (I like the shifter that comes with the TJ.)
  • Is there a reason why someone would swap out and go with the AW4, instead of swapping out with either the 32rh or the 42rle?
Sorry for all of the questions. But now you've opened a can of worms. And I'm interested.
Fourth gear on the AW4 is overdrive (.75).

The AW4 could be mounted to any Wrangler of any year. It's just a matter of figuring out the electronics.

The Cherokee uses the same shifter as the TJ.

The AW4 is a much better transmission than the 42RLE. I believe it's stronger and the overdrive in the AW4 allows you to have more power on the highway. Also, the AW4 shifts much smoother than the 42RLE. The AW4's advantage over the 32RH is that the AW4 has overdrive.

Here are three separate write-ups on Stu Olson's amazing jeep website that show how to install an AW4 into a TJ:

AW-4 Transmission Swap - 1

AW-4 Transmission Swap - 1

Introduction
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Old 08-22-2012, 11:48 AM   #6
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Quote:
Originally Posted by vertical horizons View Post
I just googled the AW4 transmission.

Less than great reviews -

The Jeep AW4 Transmissions - Novak Conversions

Not entirely bad, but they said that " ...They have a tendency to generate excessive amounts of heat, and are known for unnecessarily consuming more engine power than some other automatics. The shift points in the AW4 feel odd, and the spotty engagment of the lockup torque converter is idiosyncratic.
But, it is a decent transmission, and if kept cool and maintained, it can offer good service within its range... "

Opinions, anyone?
Don't believe Novak. Continue your search and look further. You'll see that AW4s are extremely reliable. I think Cherokees have a poor cooling system, which could lead to transmission cooling problems. With a good aftermarket transmission cooler, you won't have to worry about the AW4.
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Old 08-22-2012, 11:58 AM   #7
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The AW4 is the only automatic transmission I would even consider putting in my TJ. Go drive an automatic TJ then go drive an auto XJ. The XJ should feel quite a bit peppier. The AW4 just doesn't suck down the power like the junk 32rh and 42rle do. An auto TJ literally feels like a different vehicle than a manual TJ. I'll take the third pedal all day long.
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Old 08-30-2012, 10:15 AM   #8
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Quote:
Originally Posted by Border Dave View Post
... From 1997 to 2002 they have the 32rh 3 speed (no overdrive).

2003 to 2006 has the 42RLE 4 speed with overdrive...
Is the OVERDRIVE the 4th speed in the 42RLE, or are there 4 speeds PLUS an Overdrive?
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Old 08-30-2012, 10:18 AM   #9
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Quote:
Originally Posted by vertical horizons View Post
Is the OVERDRIVE the 4th speed in the 42RLE, or are there 4 speeds PLUS an Overdrive?
4th = OD.

Quote:
Originally Posted by Imped View Post
An auto TJ literally feels like a different vehicle than a manual TJ.
Amen to that. As a 42RLE owner, for street & highway driving, I feel the auto makes the 4.0L anemic vs the 5-speeds and 6-speed I've driven. I'm strongly reconsidering converting my auto to a manual later down the road...
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Old 08-30-2012, 10:29 AM   #10
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Quote:
Originally Posted by UnlimitedLJ04 View Post
4th = OD.


Amen to that. As a 42RLE owner, for street & highway driving, I feel the auto makes the 4.0L anemic vs the 5-speeds and 6-speed I've driven. I'm strongly reconsidering converting my auto to a manual later down the road...

I agree that when I was test driving Jeeps the auto really felt slower. I understand the convenience for tricky offroading, but for daily driving and feel I like the manual transmission. I have read a few posts that stste their is a shift kit for the autos that helps with the shift feel and power on the highway. The general consensus seems to be that correct gearing is the key to making an auto or a manual perform properly.
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Old 08-30-2012, 11:17 AM   #11
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It is my understanding that the AW4 will only bolt in to a 03 or later TJ because the 97-02 TJ used a hydraulic only transmission, (32RH). I love my 32RH. I know people think an auto TJ is not a real jeep, but I don't see a difference. I have driven stick TJs with the AX-15, NV3550 and the NSG370 and I personally wouldn't care. The overdrive is nice on the 42RLE, but the transmission itself is a dog.
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Old 08-30-2012, 01:27 PM   #12
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Just curious has anyone bolted up a 700r4 behind the 4.0?? I'm sure you would need an adaptor plate but that seems to be the go to GM auto.
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Old 08-30-2012, 01:31 PM   #13
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Old 08-30-2012, 01:31 PM   #14
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Quote:
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It is my understanding that the AW4 will only bolt in to a 03 or later TJ because the 97-02 TJ used a hydraulic only transmission, (32RH). I love my 32RH.
The AW4 can be installed into any model year 4.0l TJ.
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Old 08-30-2012, 03:11 PM   #15
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Quote:
Originally Posted by Border Dave View Post
...The AW4 could be mounted to any Wrangler of any year. It's just a matter of figuring out the electronics
...
How would you go about figuring out the electronics?
FSM? Jeep Club?

Quote:
Originally Posted by Border Dave View Post
... The AW4's advantage over the 32RH is that the AW4 has overdrive...
How bad would the 32RH whine (rev) doing 60, seeing as how it doesn't have that 4th gear?

Would it hurt the 32RH to keep the vehicle at highway speeds for long periods of time, or does the torque converter come into play here?
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Old 08-30-2012, 03:14 PM   #16
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Quote:
Originally Posted by Border Dave View Post
...The AW4 could be mounted to any Wrangler of any year. It's just a matter of figuring out the electronics.

The Cherokee uses the same shifter as the TJ...
Would you need adapter brackets?
Or would the AW4 have the same bolt pattern?
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Old 08-30-2012, 03:29 PM   #17
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Quote:
Originally Posted by vertical horizons View Post

How bad would the 32RH whine (rev) doing 60, seeing as how it doesn't have that 4th gear?
I'm at 2500 RPM at 60mph, 3000 RPM at 70mph. 32rh with 32's with 3.73 gear ratio. Anything below 2000 RPM on the 4.0 really lugs the engine.
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Old 08-30-2012, 03:33 PM   #18
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Quote:
Originally Posted by vertical horizons View Post
How would you go about figuring out the electronics?
FSM? Jeep Club?



How bad would the 32RH whine (rev) doing 60, seeing as how it doesn't have that 4th gear?

Would it hurt the 32RH to keep the vehicle at highway speeds for long periods of time, or does the torque converter come into play here?
Highway speeds don't harm the 32RH in the least, it was designed for highway use. Rev-wise, your engine rpms will be right where they should be if the axles are geared as they should be like 4.10 for 33" tires.

Electronics-wise, the main issue is controlling (turning on and off) the AW4's lock-up torque converter. I'd think that could be done more easily with a '97 to '02 TJ with a PCM that is programmed for the 32RH which also has a locking torque converter. There's a bit more wiring involved than that but that's the issue most have the most problem with. Some just install an on-off switch to enable/disable the torque converter lockup solenoid.
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Old 08-30-2012, 03:56 PM   #19
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... Some just install an on-off switch to enable/disable the torque converter lockup solenoid.
So, they manually flip a switch every time they get up to highway speed?
Or, do you mean that the on-off switch switches automatically?

I don't mean to sound stupid.
I just want to understand.
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Old 08-30-2012, 04:04 PM   #20
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As stupid as it sounds, and I would not do it this way, yep some just manuallyl throw the switch each time they get up to cruising speeds and turn it off the rest of the time.
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Old 08-30-2012, 04:43 PM   #21
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Here's an article that might help.

Campbell Jeeps - TJ AW4 Swap

While I don't have any experience with the AW4 myself, I don know a couple of friends that have successfully transplanted them into a full-size Jeep. Quite a bit larger and heavier than a XJ.

The torque converter is what makes fewer gears work. It multiplies the torque and allows fewer gears to do the work of more gears in a manual.

There are quite a few other articles available on the transmission control module that the XJ uses to control the AW4 if you to look for them.
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Old 08-30-2012, 07:35 PM   #22
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Just to add to the confusion... it seems to me the majority of TJs with the 32rh came with 3.07 gearing while the majority of those with the 42rle came with 3.73 gearing. I've owned and daily driven both. It's not a huge difference in rpms between the two at highway speeds. Also, I can remember both of of the ones I had with the 42rle having a considerably higher stall speed in the converter.
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Old 08-30-2012, 09:08 PM   #23
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Quote:
Originally Posted by vertical horizons View Post
Would you need adapter brackets?
Or would the AW4 have the same bolt pattern?
Quote:
Originally Posted by vertical horizons View Post
How would you go about figuring out the electronics?
FSM? Jeep Club?
If you read the websites that I posted in Post #5, they will answer all those questions. I don't believe any of the write-ups cover 2003+ swaps specifically, but they tell you what you need to do to get it to work.
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Old 08-31-2012, 08:03 AM   #24
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As stupid as it sounds, and I would not do it this way, yep some just manuallyl throw the switch each time they get up to cruising speeds and turn it off the rest of the time.
I think having to use that switch would be the deal-breaker for me.
To go through the whole process of making the swap, just to have to manually flip a switch EVERY TIME I get up to highway speed, plus you have to remember to flip the switch back off once you slow down.

I am looking for a TJ to be my DD.
In Houston, on my commute to work, there are times that I am cruising at 55. Other times, we are at a crawl.

If I had to keep flipping that switch on & off every time I reached 55, I think I'd be needing a new switch pretty quick.
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Old 08-31-2012, 08:08 AM   #25
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I suppose you could always install that switch on your steering wheel, like the steering wheels that have the shifting paddles. :eek

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