How do you use your 42RLE overdrive?

[Yuan]

Have been driving a 2006 LJ (auto) for several weeks, including a road trip to New Hampshire last week. From reading on this forum I understand that the 42RLE isn't the best transmission mated with the straight 6. My own driving experience seems to ascertain that perception--I do find that the O/D kicks in too soon and keeps the RPM too low. Not really an issue for around town, but on the freeways, at least on a couple occasions, the slow acceleration/low RPM turned out to be a bit problematic when merging into traffic and overtaking/switching lanes. Wondering if there are driving techniques one can employ to overcome the transmission's weaknesses somewhat. At the moment, I am considering the idea of turning O/D off entering the freeway and turn it on once approaching cruising speed(60mph maybe). Would doing something like this 1)be helpful at all and 2) cause damage to the transmission/powertrain over time? Any ideas/suggestions? LJ runs 265/75/R15 tires--slightly larger than the factory 30 inch, but not by much. Thanks.

 

[Chris]

Don't use it, period.

Get in the vehicle, turn it on, immediate turn the overdrive off, period, end of story.

Assuming your TJ is geared properly, the only time I could ever see using it would be on the highways at speeds of maybe 70 MPH plus. Beyond that, I would never, ever leave it on.

 

[Yuan]

Don't use it, period.

Get in the vehicle, turn it on, immediate turn the overdrive off, period, end of story.

Assuming your TJ is geared properly, the only time I could ever see using it would be on the highways at speeds of maybe 70 MPH plus. Beyond that, I would never, ever leave it on.

Good to know. Was very, very tempted to do just that on my drive back from NH. Thought I'd ask around here first. Build sheet says it's 3.73. I have reason to believe that's still the case. Thanks Chris.

 

[AndyG]

X2. Fear not the button.

In any scenario, turn it off. The transmission will likely last longer, it will perform better, and the higher RPMs are negated by the lower throttle body opening as far as mileage.

It's useless as tits on a boar hog.

It simply isn't designed correctly for the 4.0 's power/torque curve...the right things just don't happen at the same time with this combo.

My 06 has 4:10 gears , and I turn it off every time I start the engine. You essentially make it a 3 speed when you do that.

I don't know if anyone has ever altered the shift points on one, but it would be nice to know if it could be done.

 

[Juggernaut]

X2. Fear not the button.

In any scenario, turn it off. The transmission will likely last longer, it will perform better, and the higher RPMs are negated by the lower throttle body opening as far as mileage.

It's useless as tits on a boar hog.

It simply isn't designed correctly for the 4.0 's power/torque curve...the right things just don't happen at the same time with this combo.

My 06 has 4:10 gears , and I turn it off every time I start the engine. You essentially make it a 3 speed when you do that.

I don't know if anyone has ever altered the shift points on one, but it would be nice to know if it could be done.

Andy, as an fyi if you search my previous posts, I’ve commented on adjusting the shift points via the HPTuners program. 05&06 models only.

 

[dale5150]

I turn mine off when starting and only engage it if I am going to be over 60 or so for a long period on relatively flat ground.

 

[Jerry Bransford]

Andy, as an fyi if you search my previous posts, I’ve commented on adjusting the shift points via the HPTuners program. 05&06 models only.

That may affect when it shifts but it doesn't fix or change its .69 Overdrive ratio which is the real problem.

The only fix for that is regearing the axles to a lower ratio.

 

[Irun]

I know some don't like it, but the 42RLE isn't as bad as the internet makes it out to be. I've had several and they have all proven themselves to be reliable, with the one in my previous '03 going 190K miles before it gave up. Also, some of the 42RLE related problems were not actually the transmission, but rather Chrysler bumbling the '05 - '06 PCM changes. They knew they had a problem with the PCM and just abandoned customers who bought them. Thank goodness for WranglerFix, because they took on solving a problem Chrysler wouldn't!

That said, the overdrive and shift points aren't ideal, but gearing can help with the drivability, to a point. Making the transmission last isn't difficult, if you follow these guidelines:

- Overdrive - leave it off in town and on during highway driving
- Install a good stacked plate transmission cooler and temperature gauge
- Change the fluid regularly, using only ATF4 and
- Re-gear the differentials, based on tire size

 

[Juggernaut]

Of course it doesnt change the mechanical ratio. It does however put the engine RPM's higher so that when it does shift to 4th, the engine can still be making somewhat reasonable power to pull the horrid ratio.

 

[Yuan]

I turn mine off when starting and only engage it if I am going to be over 60 or so for a long period on relatively flat ground.

good to know. thx. plan to give it a try today.

 

[Yuan]

X2. Fear not the button.

In any scenario, turn it off. The transmission will likely last longer, it will perform better, and the higher RPMs are negated by the lower throttle body opening as far as mileage.

It's useless as tits on a boar hog.

It simply isn't designed correctly for the 4.0 's power/torque curve...the right things just don't happen at the same time with this combo.

My 06 has 4:10 gears , and I turn it off every time I start the engine. You essentially make it a 3 speed when you do that.

I don't know if anyone has ever altered the shift points on one, but it would be nice to know if it could be done.

It's useless as tits on a boar hog.--have seen some creative use of the English language on the forum. this one is right up there with all the other gems!

 

[MillAlien]

I click OD to off when my hand leaves the ignition key and I wish the default was Off not On. The 42RLE’s “4th gear” .69 ratio combined with non-stock tire sizes on stock axle gears and questionable non-adjustable shift points makes the OD “feature” pretty useless for most.

I think the practical solution to keeping the 4L in its powerband is axle re-gearing.

 

[suicideking]

I only turn on the overdrive when on the freeway and over 65mph. I also might leave it on while driving down a mountain at over 45mph.

I'm on 37's with 5.38 gears. So I'm sure that's not helping my OD.

 

[AjRagno]

Overdrive off = torque converter clutch lockup in 3rd gear with 1:1 ratio

Overdrive on = torque converter clutch lockup in 4th gear (overdrive) with 0.69:1 ratio.

Though the gearing in overdrive is not great, it’s the TCC lockup that reduces the RPMs and effectively makes overdrive useless in many situations.

It’s not as simple as keeping overdrive off at all times because now the PCM is going to lockup the TCC too soon in 3rd. Instead, learn what gear you’re in and when the TCC is locked up.

With 3.73 gears and 31” tires, keep overdrive ON from 0-40 MPH and overdrive OFF 40-60 MPH. If you come to a hill in overdrive and the engine lugs, rather than forcing a downshift, keep steady throttle and turn overdrive off. This will unlock the TCC, downshift from 4th to 3rd, the TCC will lockup again in 3rd with a 1:1 ratio and you’ll have plenty of pulling power while also keeping the heat down.

The only real control you have with this transmission is the overdrive on/off switch. It does nothing more than control whether you will shift into 4th and which gear TCC lockup occurs.

 

[freedom_in_4low]

every now and then I start thinking maybe it wouldn't be so bad to get an auto LJ, and then a thread like this pops up.

Just my opinion, but even regearing doesn't really fix the issue. It's not solely the OD ratio that's the problem, it's also the difference in ratio between OD and 3rd gear being such a jump.

Say you have 35's and 5.13s. Cruising along at 75mph puts you at about 2660rpm. Not horrible for flat territory, but say you're in Colorado with a little less power due to the elevation, and you're trying to climb a modest grade. Now you really want to be around 3k, but dropping to 3rd puts you all the way to 3900. I'll get to 3900 when I need it, but it would annoy me to just hang out there to be able to maintain speed. So there's no happy spot.

5.38 is a little better but really I'm not sure I'd like anything less than 5.89, and I'm not sure how available that is (definitely out for a Dana 30, maybe for 44?) or what kind of vibration issues you might discover with that driveshaft speed.

It almost makes more sense to go 4.56 so at least your 3rd gear is somewhat sane and just forget OD ever existed.

But, this is all from a guy currently running 4.88 with 32s and an AX15, so clearly I'm not afraid of some rpm.

 

[Yuan]

Overdrive off = torque converter clutch lockup in 3rd gear with 1:1 ratio

Overdrive on = torque converter clutch lockup in 4th gear (overdrive) with 0.69:1 ratio.

Though the gearing in overdrive is not great, it’s the TCC lockup that reduces the RPMs and effectively makes overdrive useless in many situations.

It’s not as simple as keeping overdrive off at all times because now the PCM is going to lockup the TCC too soon in 3rd. Instead, learn what gear you’re in and when the TCC is locked up.

With 3.73 gears and 31” tires, keep overdrive ON from 0-40 MPH and overdrive OFF 40-60 MPH. If you come to a hill in overdrive and the engine lugs, rather than forcing a downshift, keep steady throttle and turn overdrive off. This will unlock the TCC, downshift from 4th to 3rd, the TCC will lockup again in 3rd with a 1:1 ratio and you’ll have plenty of pulling power while also keeping the heat down.

The only real control you have with this transmission is the overdrive on/off switch. It does nothing more than control whether you will shift into 4th and which gear TCC lockup occurs.

thanks. just got back from a test drive. starting to see how this makes sense. Chrysler sure made this one interesting.

 

[suicideking]

every now and then I start thinking maybe it wouldn't be so bad to get an auto LJ, and then a thread like this pops up.

Just my opinion, but even regearing doesn't really fix the issue. It's not solely the OD ratio that's the problem, it's also the difference in ratio between OD and 3rd gear being such a jump.

Say you have 35's and 5.13s. Cruising along at 75mph puts you at about 2660rpm. Not horrible for flat territory, but say you're in Colorado with a little less power due to the elevation, and you're trying to climb a modest grade. Now you really want to be around 3k, but dropping to 3rd puts you all the way to 3900. I'll get to 3900 when I need it, but it would annoy me to just hang out there to be able to maintain speed. So there's no happy spot.

5.38 is a little better but really I'm not sure I'd like anything less than 5.89, and I'm not sure how available that is (definitely out for a Dana 30, maybe for 44?) or what kind of vibration issues you might discover with that driveshaft speed.

It almost makes more sense to go 4.56 so at least your 3rd gear is somewhat sane and just forget OD ever existed.

But, this is all from a guy currently running 4.88 with 32s and an AX15, so clearly I'm not afraid of some rpm.

I had a manual and switched to auto. The only time I miss the manual is going uphill and driving up a mountain.

 

[MillAlien]

Overdrive off = torque converter clutch lockup in 3rd gear with 1:1 ratio

Overdrive on = torque converter clutch lockup in 4th gear (overdrive) with 0.69:1 ratio.

Though the gearing in overdrive is not great, it’s the TCC lockup that reduces the RPMs and effectively makes overdrive useless in many situations.

It’s not as simple as keeping overdrive off at all times because now the PCM is going to lockup the TCC too soon in 3rd. Instead, learn what gear you’re in and when the TCC is locked up.

With 3.73 gears and 31” tires, keep overdrive ON from 0-40 MPH and overdrive OFF 40-60 MPH. If you come to a hill in overdrive and the engine lugs, rather than forcing a downshift, keep steady throttle and turn overdrive off. This will unlock the TCC, downshift from 4th to 3rd, the TCC will lockup again in 3rd with a 1:1 ratio and you’ll have plenty of pulling power while also keeping the heat down.

The only real control you have with this transmission is the overdrive on/off switch. It does nothing more than control whether you will shift into 4th and which gear TCC lockup occurs.

Interesting info - I was wondering how/when the TCC lock-up worked.

I did, at first, switch the OD off & on as you suggest, but...I'm not always paying attention so I now default to switch off at start-up. I sometimes re-engage the OD and also force downshift, but most of the time when I'm just puttering on asphalt in daily-driver mode I leave it off. If I'm on the trail then I manage the OD and gear selector more carefully. But good advice either way - thanks!

I'm running 32s, about to move to 33s and re-gear to 5.13. The axle gear I have now (3.73) is my primary gripe about the whole system and not the 42RLE and the OD monkey-business. Looking forward to scraping enough $$ together to re-gear.

 

[Yuan]

Drove the LJ today with O/D on and off at different speeds--just for the heck of it. LOVE the throttle response and acceleration with O/D off around 40-65 mph range. Wondering why Chrysler did what it did with the o/d feature. Well, at least now I know what button to push when the RPM wouldn't go beyond 2k.

 

[Apparition]

I rarely mess with mine. Sometimes I’ll flip it off to pass on interstate but see no reason to mess with it on 25-35 mph streets.