3rd or OD in the mountains

[Burbski]

Hi - I have a 1996 Suburban 2500 7.4 4L80e and will be towing a good amount in the mountains this summer. It is a small trailer (~3000 lbs) without trailer brakes.

Do you think I should be towing in 3rd or OD, or a combination depending on the hills vs flat?

I know I should eventually get a trans cooler, any recommendations on ones you like? Will the cooler have any adverse effects in the winters, it regularly gets below zero where I live?

As always, thanks for your thoughts.

 

[1998_K1500_Sub]

Flat: Whatever gear gives you satisfactory throttle response in the thin air

Hills: 3rd or lower, depending on grade and engine braking objectives

The engine will be down on torque, e.g., at 6000' elevation the max MAP is around 24", vs. ~30" at sea level. Idle MAP is around 10", so at 6000' the net usable torque is down about (24-10) / (30-10) = 70% of what's available at sea level... "back of the napkin" anyway. It'll be hard to abuse the tranny with that much torque deficit.

Let's see what others say.

 

[Drunkcanuk]

Hi - I have a 1996 Suburban 2500 7.4 4L80e and will be towing a good amount in the mountains this summer. It is a small trailer (~3000 lbs) without trailer brakes.

Do you think I should be towing in 3rd or OD, or a combination depending on the hills vs flat?

I know I should eventually get a trans cooler, any recommendations on ones you like? Will the cooler have any adverse effects in the winters, it regularly gets below zero where I live?

As always, thanks for your thoughts.

I would think with the 4l80 and a relatively low weight trailer, you should be fine most of the time. But wouldn't hurt to drop a gear during a harder climb.

Maybe get a dongle thingy for the OBD2 port and some app to keep track of the trans temps.

As for the winter and a cooler, don't worry about that at all. I'm from the frozen north and one of my trucks has a trans cooler, once it's warmed up, there is no difference from when it's warm out.

 

[1998_K1500_Sub]

Maybe get a dongle thingy for the OBD2 port and some app to keep track of the trans temps.

At least one inexpensive app allows monitoring of the transmission temp, see comments in this post and throughout the thread https://www.gmt400.com/threads/bluetooth-obd2-adapter.66932/post-1407696

 

[RichLo]

3K trailer, dont worry about it. Run it in OD... it'll downshift if it needs to. Your drivetrain (not suspension) is built to run a 10,000lb GVW Dually with a bed full of bricks.

If it was a 4L60, I'd say go to 3rd in the hills.

And yea, for any 1996+ truck I'd recommend getting the trans temp app on your phone or tablet just because its so simple.

 

[L31MaxExpress]

3K trailer, dont worry about it. Run it in OD... it'll downshift if it needs to. Your drivetrain (not suspension) is built to run a 10,000lb GVW Dually with a bed full of bricks.

If it was a 4L60, I'd say go to 3rd in the hills.

And yea, for any 1996+ truck I'd recommend getting the trans temp app on your phone or tablet just because its so simple.

Engine and transmission are actually built to pull a near 20K lbs vehicle. The P30 motorhomes use the same units.

 

[skylark]

Engine and transmission are actually built to pull a near 20K lbs vehicle. The P30 motorhomes use the same units.

Not saying that you're wrong because I don't know but I have to wonder if it really wasn't built for 20k but if instead they used it and found out that it worked.

 

[L31MaxExpress]

Not saying that you're wrong because I don't know but I have to wonder if it really wasn't built for 20k but if instead they used it and found out that it worked.

I may still have a copy of the GM Powertrain data sheet on the 4L80E. GM Engineers put specific numbers to the 4L80Es capabilities and sold them to several other vehicle manufacturers as well. AM General, Bentley, Jaguar, Rolls Royce, and Workhorse to name a few. I believe even Aston Martin used the 4L80E in some of the DB7s.

 

[Pinger]

I know I should eventually get a trans cooler, any recommendations on ones you like? Will the cooler have any adverse effects in the winters, it regularly gets below zero where I live?

Consider plumbing a cooler through a thermostat.

 

[Burbski]

Flat: Whatever gear gives you satisfactory throttle response in the thin air

Hills: 3rd or lower, depending on grade and engine braking objectives

The engine will be down on torque, e.g., at 6000' elevation the max MAP is around 24", vs. ~30" at sea level. Idle MAP is around 10", so at 6000' the net usable torque is down about (24-10) / (30-10) = 70% of what's available at sea level... "back of the napkin" anyway. It'll be hard to abuse the tranny with that much torque deficit.

Let's see what others say.

Thanks!