Stuck in 1st gear while towing uphill

[ofishl1]

Pulling our loaded toyhauler up a 7% grade dirt road at 9000ft in our 23 Laramie crew CTD 4x4 on a lot of washboard had to go slow, but when I tried to speed up the torque converter seemed to be locked up and stayed in 1st gear even past the RPMs it should have shifted ..slowed to a stop started again and sped up to where it should have gone to 2nd gear, but would not, Tranny temp hit 230 by the time we got the top of the long grade and took a mile at 10 to 15 mph (ruff road) before it started coming down slowly and hung around 200. Now concerned why it did that and is the Tranny fluid trashed from the high heat? Thoughts on the 1st gear lock out and the high heat potential damage to oil?
Thank you,
ERJ

 

[Brutal_HO]

Converter won't lock in 1st, that's why your temps went up. 230 is nearing the upper limit where ATF+4 might start to break down (240-250) but probably not of great concern if it's not overdone.

If you're on the ragged edge of an upshift, sometimes a slight let off on throttle can force an upshift then it might stay in 2nd, where you'd have a better chance of lockup.

Ultimately, if you need lockup at those slow speeds you either need to run in 4-Lo or do a custom tune to get 1st gear TC lockup.

With your truck, I would have pulled that in 4-Lo*.

* Now, for the 4-Lo thing, a BD Diesel 2-LO UNLOC kit is the best cheapest solution if you need to run in Low range on pavement or don't otherwise want the front axle engaged. Mine is wired to one of the Aux switches.

 

[ofishl1]

I was running in 4 Hi, and thought maybe that held the the gear, I did back off several time tines and tried to accel to the point the revs were high enough to promote a shift but she stayed put...on the 200 mile highway run home tranny temp ran 170 to 190 as normal pulling mountain grades

 

[ofishl1]

Never pulled such a long dirt grade like this before under heavy load, may have been a fluke, probably change the oil regardless..

 

[AH64ID]

Definitely use 4-Lo if you’re in 1st and getting above 200°, there are a few stretches of road I have to do this on for hunting.

1st will run cooler than 2nd below 20 mph because of the coolant flow and neither gear will lock that slow, so you likely would have been hotter had it shifted.

Are you sure ERS didn’t have you locked in 1st?

Ultimately, if you need lockup at those slow speeds you either need to run in 4-Lo or do a custom tune to get 1st gear TC lockup.

I don’t know about the 68RFE, but the Aisin won’t lock any slower in 4-Lo than it will in 4-Hi, I’ve tried many times with slow dirt road towing and it still takes ~20mph.

 

[ofishl1]

BY ERS you mean 4Hi?

 

[ofishl1]

..by being in 4Hi I mean

 

[ofishl1]

I am wondering if the combo of 4Hi and TowHaul created this condition

 

[AH64ID]

BY ERS you mean 4Hi?

ERS is Electroinc Range Shift, where you can limit the top gear with the + and - buttons on the steering wheel. If it was in 1 you would be limited to 1st, which is what it sounds like.

I am wondering if the combo of 4Hi and TowHaul created this condition

No, that will have no effect on the trucks ability to up shift at the proper rpm.

 

[ofishl1]

Oh , right the manual selector on the steering wheel, no I hadn't messed with that intentionally..however I have found myself bumping that before and being locked in a gear, maybe a Longshot I hit it while dodging washboard...good point to consider.

 

[H3LZSN1P3R]

What RPM were you holding? In tow haul and in 4wd high it actually does not surprise me if it was holding 1st given the conditions

 

[ofishl1]

Around 15 to 1800

 

[H3LZSN1P3R]

Around 15 to 1800

Oh thats not high at all i would not have wanted a shift to second you would be lugging and killing the trans and engine faster, 15-1800 is where the cummins makes the peak power so there was nothing wrong really unless you went to 4LO there was no better way

 

[AH64ID]

That's definitely normal, and not past the rpms where it should have shifted. You would certainly have cooked the trans fluid if it had shifted to 2nd.

When I'm pulling heavy trailers up steep dirt grades I like to be around 2500 rpms in 1st gear, when the road permits, as that keeps the temps down.