Trailer towing with 33's??

Noob posting here, though I've been reading for lots of years, and picked up lots of good tips and ideas.

I just upgraded my tires from the stock 31x10.5's on 15" rims to 17" rims and 285-70R17 tires. Looks Bad @ss!! Truck is a '98, 160K miles, supercharged with the URD fuel system upgrades, so power is not a problem. Also have a 3" susp lift, but the front mud flaps rub a bit at the extremes of steering, but not otherwise. Not a big concern for me at this time.

My question is around towing. I took a trip up the N Cascades highway and the tranny temp (aftermarket gauge) ran quite hot, peaking at about 260* for a couple of minutes. Luckily the pass flattened out and I was able to get the torque converter to lock up and it quickly cooled back to 180. The A/T temp light did NOT come on. The truck was essentially unloaded, but made me quite concerned for what might happen in warmer weather as this was a cool day (not more than 60F), and I'm likely to make the other trips with several hundred pounds of gear, and eventually a small travel trailer, and I'd like the truck to live through it...

I do have an aux tranny cooler on it, but probably not optimally mounted-about 1/4 blocked behind the front license (which I'll relocate this weekend), and I could drill some holes in the lower bumper fascia to increase airflow through there also.

The pass is too curvy to keep it consistently above 50 mph to keep the converter locked, so increased heat is likely unavoidable.

What would my best options be? Re-gear the diff's? I still have the stock 3.91's. I could add a 2nd tranny cooler on the drivers size to increase the cooling that way, has anyone done that? I'm currently plumbed to run through the aux cooler first, then the stock cooler in the radiator then back to the tranny.

If any of you done towing with similar tire size/gear ratios I'd like to know how you kept things cool going uphill and avoided cooking your tranny. I'd like to make 200-250K before I need to do a level 10 rebuild.

Thanks!

 

4.88 re-gear

3.91 is just nuckingfutz on 33's

my buddy retains his factory 4.10 gear ratio on his double cab...
wheels that on 33's (33.1 nom)...
but installs 265's when not wheeling.

He has an additional tranny cooler...
but temps still get a little high when wheeling hard.

Buddy is intending on swapping to 4.88's soon.

I say 4.88's because it's an auto trans.

I roll 4.88 on my extcab 5-spd with 295's.
But utilized 285's for much of my junks wheeling history.
I'll drag my trailer thru just about any trail.

for the entertainment of that...

https://youtu.be/pibS4xWF19M

https://youtu.be/c6BjCnI511I

https://youtu.be/-PkPNmaq1r8

https://youtu.be/0YXqv08F04A

At the very least... go with a 4.56 gear ratio

 

Couldn't tell from your post if you're doing this or not, but the first thing you need to do is push the button to lock the transmission out of overdrive while you're climbing hills. This will help cool your transmission fluid substantially.

Second thing is that I believe you have your transmission fluid routed incorrectly. By running it through the aux. cooler first, it cools the fluid down, but then running it through the stock cooler next heats it back up to ~190 degrees, because that is what the engine coolant is. I think you would do better to route it through the stock cooler first, and then your auxiliary cooler.

 

Thanks for the vid's, Taco Dell, fun to watch.

Robb I thought about those ideas myself also. I notice when the torque converter locks that things cool down pretty quick. Gonna try that w/the O/D off and see if it's the same. I wondered about the tranny fluid routing, it's simple enough for me to swap the flow around as you suggested also. I'll give them both a try in a couple of weeks when I have another chance to get out and up in the hills.

My other option would be to buy smaller tires and rims for use when I do trailer. I need at least 16" rims though as I'll be doing the Tundra brake upgrade soon as well, so my stock 15" rims will no longer fit.

Thanks again, both for the replies!

 

Definitely lock out the OD and try it again. If your aux cooled tranny hits 260 while climbing with a basically empty truck, on a cool day, you’re smoked with a loaded trailer. If that doesn’t work, try the reroute and gearing, etc.


I live by the ocean (flat), so I haven’t climbed any mountains (yet), but my rig below has never hit 260. I don’t even have a cooler (yet).

 

Subed for when I'm not work, so that I watch the videos

 

Thought I'd post here again and let you know how things have progressed.

First, Robb, I do debate your contention a bit, not on the principle, but on the numbers used. I have an aftermarket water temp gauge plumbed into the engine coolant outflow tube from the top if the engine to the radiator. I rarely see 190* on that gauge, so I know the coolant in the bottom of the radiator is going to be significantly below that. Nonetheless, I see the point that if the engine coolant is warmer than the tranny fluid, than the TF is going to be carrying that heat back to the tranny. I replumbed to go through the stock cooler first then the aux cooler.

Next, as the aux cooler was at least partially below the lower bumper fascia and thus blocked from getting full air flow, I drilled a series of 1 inch holes on 2 inch centers in the bumper plastic to increase airflow thru the aux cooler. Put in 15 altogether, and have some coarse-mesh screening mounted behind them just in case a rock takes aim at me.

With those changes, I've now made two trips over Snoqualmie Pass (not that high, just over 3000' at the summit). Using the O/D lockout in combo with the other changes has made a *HUGE* difference. Somehow I had it in my little brain that using the O/D cancel switch also kept the torque converter from locking. It does not, it just locks at a higher RPM. But I can see the tranny temps drop 10 + degrees w/in a few seconds after lockup, and continue to stay w/in the normal range w/the engine running at higher revs. If I delay cutting out the O/D I can get it up to 180, but then I cut out O/D and it drops quickly. I"m much more confident in future towing now.

I checked my mileage on the last trip to Ellensburg and back, and still got about 18.5 MPG so I"m comfortable w/that as well.

As I got it pretty hot just before my first post, and I want to ensure longetivity, I'll have the fluid changed out in a couple more weeks.

Thanks again for the advice, guys!