I know this topic has been discussed but I'm hoping someone knows something that could help. I have grown tired of my transmission not wanting to shift out of third into OD while going up a incline on the highway. Then when it finally shifts into od, it doesn't have enough power to keep momentum. So I'm left with keeping it in third and redlining it. I have 36" tires and 5.13 gears. Any help would be greatly appreciated
Changing the 42RLE shift points?
- Thread starter 2005RubiconTJ
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Brianj5600
TJ Expert
The .69 overdrive in the 42rle drops RPMs so much it is asking a lot of the 4.0. Look into HP Tuners. You should be able to adjust shift points and possibly pick up some power with some timing advance.
My 04 could not pull OD on flat ground with stock gears and 35s. I know, I know, but that's the it was when I bought it. I have 5.38s on order and should be here by the end of this month. In the meantime I have been making some changes to the tune and OD is semi useful. The 04 past about half throttle didn't seem to do much and past 3/4 throttle may have lost power. I added timing down low at the load and RPM it struggled at in OD and it helped. With your 5.13s and some PCM tuning you might not need to change shift points. @Chris might have some info. My software is for 04 back to 87?
My 04 could not pull OD on flat ground with stock gears and 35s. I know, I know, but that's the it was when I bought it. I have 5.38s on order and should be here by the end of this month. In the meantime I have been making some changes to the tune and OD is semi useful. The 04 past about half throttle didn't seem to do much and past 3/4 throttle may have lost power. I added timing down low at the load and RPM it struggled at in OD and it helped. With your 5.13s and some PCM tuning you might not need to change shift points. @Chris might have some info. My software is for 04 back to 87?
There is no way to change the shift points on the 42RLE, plain and simple.
I've talked in depth to David Kasper (of B&G Tuning) about this, who is one of the original Chrysler engineers who helped design the PCM. I've also accessed the PCM of my 42RLE using the HPTuner suite of software, and while there is a lot you can change, anything to do with the transmission isn't part of it (including shift points).
It's unfortunate, but true. You just have to re-gear and live with it.
The 42RLE never had any place in a Wrangler IMHO. It was a transmission designed for FWD vehicles (I want to say it was a Dodge of some sort) that ended up in the Wrangler simply because it's what they had around at the time (and it made more sense then trying to design something specifically for the Wrangler).
It's not that it's actually that bad of a transmission, it's that that pesky .69 OD gear is just absolutely horrid. It never truly knows what gear it wants to be in.
I've talked in depth to David Kasper (of B&G Tuning) about this, who is one of the original Chrysler engineers who helped design the PCM. I've also accessed the PCM of my 42RLE using the HPTuner suite of software, and while there is a lot you can change, anything to do with the transmission isn't part of it (including shift points).
It's unfortunate, but true. You just have to re-gear and live with it.
The 42RLE never had any place in a Wrangler IMHO. It was a transmission designed for FWD vehicles (I want to say it was a Dodge of some sort) that ended up in the Wrangler simply because it's what they had around at the time (and it made more sense then trying to design something specifically for the Wrangler).
It's not that it's actually that bad of a transmission, it's that that pesky .69 OD gear is just absolutely horrid. It never truly knows what gear it wants to be in.
The 42RLE is good for one thing - installing a RubiCrawler.
Brianj5600
TJ Expert
Does the HPT software have all the transmission settings, but you can not change them? Syked has many, many parameters that can be changed on the transmission. Included is TPS vs RPM for 3 to 4 shift, 4 to 3 shift, WOT shift, converter lock up, etc, etc, etc. I have not tried to change things yet, but it appears to be possible.
The HPT software has a few transmission settings, but not many, and none of them are shift points. Remember that in 05-06 (the only years the HPT software works with), they combined the ECM and TCM into one module (the PCM), so that one module controls both the engine and transmission, whereas on the 03-04 42RLE, it has a separate module (TCM) for the transmission.
I'm not sure what (if anything) this has to do with it, but it would be interesting to see if you could play around with the Syked software and change anything like shift points on the 03-04 42RLE equipped models.
Brianj5600
TJ Expert
What's funny is that I talked to about 20 different transmission shops. I asked them all if there was a way that the .69 OD gear could be swapped out for something better, and they all told me it wasn't possible.
I still have a hard time believing that, but that's what every single one of them told me.
Brianj5600
TJ Expert
Gear Vendors would be like a Rubicrawler except it is an overdrive vs reduction. The transmission's OD would be turned off. Not ideal for sure.
I think I already know the answer to this, but would software at least allow you to have the OD default to 'off' at start up?
It isn't possible (IIRC) due to there not being an actual gear that can be swapped out and replaced with a better gear. The OD ratio is achieved electronically by combining the output from two of the other planetary gears in the transmission.
http://shop.ukrtrans.biz/wp-content/uploads/catalogs/42RLE.pdf
That explains the power flow through the transmission. The only way to change the OD ratio is to swap out the transmission to one with a different ratio.
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I still don't understand why or how folks struggle with that. When my hand leaves the ignition key from starting the engine, it moves ever so slightly to the passenger side of the vehicle, hits the OD off switch on the way to the shift lever. It is almost without effort. Almost.
That explains it. None of these transmission shops I spoke with explained it in detail to me, so it didn't make sense as to why that was. I thought it was just a mechanical procedure such as swapping out a gear. Clearly that's not the case.
Thanks for shedding some light on this.
@psrivats, you may find this information useful as well.
I wouldn't say that I struggle with it. However, I am on the second switch, as they do seem to be a little fragile. I don't think they were intended to be cycled so frequently. So, it's certainly not a big deal, but if I could change it?
I have always had a hunch that the OD gear was not literally another gear in the trans. This explains it. So, the next question would be, when the transmission does finally lay over, I wonder if there is any decent swaps?
The answer to this is simply no.
Unless you want to swap in a manual transmission (i.e. AX-15), your choices are limited. The AW4 swap is a possibility, but it has many drawbacks as Blaine has pointed out before. You could swap in a 32RH from an earlier model TJ as well.
Unfortunately you can't install a transmission such as the GM 4L60E for instance. It's computer controlled just like the 42RLE, and the Jeep PCM has no way of talking to it and telling it when to shift, etc.
To be honest, I can live with the 42RLE, it's not the end of the world. Sure, the OD hunting gets annoying, but if you were mostly using it off-road or for trail use, then it would be a moot point.
It's only around town and on the highway that that OD thing really started to bother me.
It's similar to how people hate the Electronic Start Stop (ESS) in modern cars and look for ways to disable it permanently though there is a switch in most vehicles.
The factory manual is not super clear about when the OD is engaged. Most cars you don't have to do anything, but the 42RLE OD comes in early enough in the TJ and the vehicle really wants to stay in OD which kind of gets annoying if you are not geared properly in the axle. Thus the recommendations you see peppered everywhere for 5.13s with 33s.
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You are supposed to caress them gently like your girlfriend, not beat them like your wife.
I too ultimately just got in the habit of turning the OD switch off anytime I start the vehicle.
At first it was annoying, but like anything else, if you do it enough, it becomes a habit. With the OD switch off, it's really not bad at all.
What I found is that I never turn the OD switch on after that unless I'm going highway speeds. Around town though, the OD stays off all the time.
At first it was annoying, but like anything else, if you do it enough, it becomes a habit. With the OD switch off, it's really not bad at all.
What I found is that I never turn the OD switch on after that unless I'm going highway speeds. Around town though, the OD stays off all the time.