4L and overdrive gears

I'm in a 2018 sr5 v6 auto with 4.88 gears on 33s. In 4L my truck will only shift to 4th gear, which if I want to go 25mph I'm spinning about 4k rpms if I remember correctly. I've tried using s mode to get into 5th and 6th but it won't go past 4th. I swear that it used to until I got the recent ecu update.

Can anyone else confirm or disprove this?

 

Consider using 4H instead of 4L at higher speeds when 4wd is needed.

 

Sorry, but that is not quite true:


@sdfuller88 , something doesn't seem right there. I have no idea what though.

I have an MT and cruise at 30mph to 35mph in 5th and 6th.

 

Okay, my bad.

What applications require 4L in overdrive?

 

I used it on an easy section after a climb. Instead of stopping and switching out for the next more difficult section, I just cruised the flat, easy bit in 5th and 6th in 4Lo. It just depends if you want to stop and switch out or not.

 

Thanks for that! I was trying to find something like that earlier but I was on page 300ish though where it talks about the features of the 4wd modes.

Are you geared and on bigger tires?


Here's the my rpms for my truck at "high speeds" in 4 low. I wonder if the computer is only looking at mph and not rpms for when to allow a shift. That doesn't make sense but maybe..... Otherwise I don't know why I can't get past 4th gear. Damn auto trannies..... I would love to be able to cruise at 30-35 for a couple minutes before getting to the next obstacle.

 

I am stock.

I believe there is an issue with the speed limiter on 5.29s? But, I think that was discussed with respect to road speeds in 2Hi? 2,200rpm in 6th should be no problem.

In the MT case, our 6th ratio and the 4.30 diff is just slightly higher gearing than the AT on 5.29s with stock tires.

 

Yea I think it is a gearing and tire size problem. Maybe I can talk to @OVTune and see if Matt has a solution for this with his 4.88 tune

 

That chart is specifically for the MT. I think the AT would be different due to the gearing.

edit: I guess your point remains the same though... you can certainly go faster than 25mph in 4L.

 

Damnit, you're right about the chart. I just noticed that. Yea I dunno why I can't get out of 4th in 4L. I'm assuming it's something to do with the tuning and/or gearing.

I'm heading back out this Saturday and will keep troubleshooting. Hopefully it's something stupid and easy.

 

Good point. It was after the MT section of the OM, but there was no max speed discussion or chart in the AT section. Fucking OM! About as bad as the TRAC section.

Other than the 5spd column, I always interpreted that page to be for both ATs and MTs.

 

While testing 2Lo mod on the road, I never got my auto to go into what felt like 5th or 6th gear, even with feathered throttle. That said, I wasnt data logging and I wasnt checking on OBDII, so I am not sure.

That is with several versions of OVTUNE, never tested it stock.

I would say that probably overdrive gears are locked out in 4Lo (and 2Lo mod) in the ECU for Auto.
Ovtune can PROBABLY fix that.
If you really want it, ask Matt
support@ovtune.zendesk.com

 

Thanks, @BigWhiteTRD .

That is really odd. If they went through the trouble of restricting the ATs, it is funny that it is not mentioned in the manual and they don't caution whatever the reason is on the MT side but actually state the opposite.

 

Agreed, but I didn't test enough to be positive... I felt it might have been an OVTUNE 'issue', so I didnt really think about it too much as the tune was still much more infancy at the time. Guessing now, not an Ovtune issue.

 

honestly you should'nt be driving in 4lo at any higher speed than 30MPH anyways... more prone to breakage, and putting more stress than you need to on the t-case.. I've tested my stock AT and couldnt get above 4th gear either.. I can only assume this is a programmed "safety" to reduce wear on the transmission, and transfer case, and limit speeds in 4lo.. I dont see this as a problem... just do the anytime locker mod...

 

I have ARB's front & rear. It's more prone to breakage spinning at 3200 rpms @ 25mph in 4th than it is at 1861 rpms in 6th. More rpms = more power. It's not like I'm flying up obstacles at 25-30 mph, I just need to go a 1/2 mile or so down the trail to the next hill....

 

No it's definitely that way from the factory. An easy way to test is using s mode to select gears. Way easier to count gears that way. It would be sweet if Matt did this cause its annoying to creep down the road or shift into 2 or 4 hi for 2 minutes then back into 4 low.