Best towing transmission - 4L-85 or 65?

wildwoodrver · October 11, 2004

I'm new to your forum, and I am in the process of specing out a new tow vehicle. I'd like to tow our 6300 pound travel trailer with a 3/4 Ton Burb or Yukon.

I need more info on the transmissions offered in GM trucks.

The brochure varies between "heavy duty hydramatic", 4L65-E and 4L85-E.

What are the differences? Which would be best for towing (staying cool, usable o'drive, etc.). I hope to have a 6.0 Vortec in front of it and 4.10s behind it.

Thanks

o4yukonxl · October 11, 2004

The transmission choice depends on which engine you get. If you option the 8.1 then you get the 4L85, otherwise you get the 4L65 with the 6.0. The 4L85 handles the higher torque of the 8.1.

I have the 4L85 and 8.1 engine, which I use to tow a 4K lb boat loaded with gear in the Mountains here in Colorado. The tranny works very well in tow haul mode, especially climbing passes. For about $850, you can signficantly improve hp and TQ. Check out my posts in high performance.

wildwoodrver · October 11, 2004

Thanks for the input.

I was interested to see you are running 3.73 ratio. I've been leaning toward the 4.10, as everyone says it is best for towing. Also wanting to stay with the 6.0 for improved solo fuel economy.

I would think the power is adequate with the 6.0, and I want to spec in some margin of safety and durability. I'm still smarting from having to replace my gearbox in the '96 Dodge 3/4 ton, Cummins, Banks at 108,000!

042500HD · October 12, 2004

I have the 6.0l and i have the beefier trans the 4L80-E to be exact.

o4yukonxl · October 13, 2004

The auto tranny that is paired with the vortec 6000 has an RPO code of MT1, which is the 4L80E. On 2500 Surburbans and Avalanches, the auto tranny that is paired with the vortec 8100 has an RPO code of MN8, which is the 4L85E. The two transmissions have the same gearing, but the 4L85E is rated for more weight.

The gas mileage difference between the 8.1 and 6.0 is not that great if your running 4:10 gears. I tow with the 3.73s and get 12 around town and 13-13.5 on the highway. If you get a chance, drive them both before you decide.

dannyukonxl · October 13, 2004

the 4l80e has 4 planetary gears and the 85 has 5, if your going to be towing a lot then get the 4.10s , do NOT get the 4l65e , that is not made for towing much more than 3000 pounds for more than 20k miles, anyways i think im gonna stick a shift kit in mine and maybe some tuning like 04yukon xl did, if you want to stick with a 6 liter then get the 2500 suburban you'll be happy you did but get the 410's not the 373's, you will be challenged for torque, as far as gas mileage, my neighbors denali with 20's gets 14 on the highway and not much more than mine in town,and now i hear its pretty hard to come by a 6 liter yukon xl b/c the factory equips them with the 8.1 since they're going to be towing more anyways, by the ways the 80 series are based off the th400's in the old muscle cars, only internals are different