Down the Mountain - Drive or 3rd or 2nd?

[fraser jim]

just spent $ 1,500 on my 04 66k K1500 Suburban to rebuild transfer case.

We drive over Berthoud Pass in Colorado just about every weekend.

It is about a 10-mile ascent/descent and about 3,000 feet up/down with some 15mph 180degree switchbacks.

Mostly in 2HI, some in Auto 4WD, and if it really lousey, in 4WD.

I will usually drop into 3rd for the climb and leave it in third for the descent. Speeds are normally 35-50mph.

If someone is real slow, and holding up traffic on the descent, I will drop it into 2nd?

I know that brake material is cheaper than rebuilding transmission.

Any recommendations??

Thanks

Fraiser Jim

[jdmccright]

Wow, someone from my alma mater...had to give a shout out for that! Driven that road many times also, though not in a nice 4wd Sub (Ref: Merc Bobcat...I was one of those slow-ass cars in front long ago!).

If you find yourself hitting or dragging the brakes constantly just to keep from eating the guy's bumper, you'll do better to shift into 2nd. You'll save yourself a pair of cooked warped rotors. The caveat to this braking method is increased tranny fluid temps. So, for any significant mountain trekking, a separate tranny cooler should be installed if not included as a factory option. And yes, I'd probably go with shorter fluid change intervals for the tranny and transfer case. The blue stuff ain't cheap but it's cheaper and easier to change than a xfer case.

Hope this helps!

[j cAT]

[quote=fraser jim;6068298]just spent $ 1,500 on my 04 66k K1500 Suburban to rebuild transfer case.

We drive over Berthoud Pass in Colorado just about every weekend.

It is about a 10-mile ascent/descent and about 3,000 feet up/down with some 15mph 180degree switchbacks.

Mostly in 2HI, some in Auto 4WD, and if it really lousey, in 4WD.

I will usually drop into 3rd for the climb and leave it in third for the descent. Speeds are normally 35-50mph.

If someone is real slow, and holding up traffic on the descent, I will drop it into 2nd?

I know that brake material is cheaper than rebuilding transmission.

Any recommendations??
Quote:

I have always used the down shifting to slow speed when decending a steep grade. using the brakes can be dangerous as the pads/fluid get hot then if by chance you need to stop quicly you could loose all braking power..in you owners manual it states using the transmission in a lower gear on climbing and decending steep grades..

with the use of the vehicle on this type of road conditions replacing the drive train fluids is needed more often..


with decending in a lower gear the engine coolant has plenty of capacity to cool the transmission...

when climbing the engine and transmission will get hot, use of a lower gear will reduce the temp of coolant..

in the summer in the arizona desert/mountain areas I seen this work quite well with the air temp at 110deg f..

no mountains where I live...and no temps in the 100's..so that was an interesting experience.

[Elbert]

I've read where not good to use the "auto" function on the transfer case...you may want to check into that.

[iroc343]

You need to talk to someone familiar with this tranny and it's power flow. I know on the Turbo 350 and 400's shifting into the actual gear was better for the transmission because it applied the bands in addition to the sprags. This transmission is a cousin to the 350 and 400 so I am sure the same probably applies.
As for the trans cooler, the factory cooler, even with the towing package, is inadequate for towing. A large aftermarket cooler should be installed in-line with the factory unit. The cooler the better as far as tranny fluid goes.

[j cAT]

Originally Posted by Elbert

I've read where not good to use the "auto" function on the transfer case...you may want to check into that.

the use of any 4X4 operation at anytime on solid dry pavement is not recommended...this is as written in the manual a part time 4X4 drive train..

operation in any 4X4 position on other road / off road unpaved surfaces is fine...the auto 4WD is very fast . so fast you should not be able to detect when it cuts in and out...in snow and in very wet heavy rain conditions I use auto 4WD...

what is bad for these drive trains is not replacing these fluids...many have been hurt with not doing the correct change out intervals...

[Elbert]

I have a 2001 K2500 Sub with the 496 engine and 4L80E transmission (I think those are the right numbers)...anyway I have the switches on the dash for 4wheel drive and "Auto" is one of the selections. Its a given you don't engage 4 wheel drive on dry pavement. If conditions were appropriate for 4wheel drive, I would simply select 4wheel HI and leave it engaged until the conditions changed such that 4wheel drive was not needed. I don't use the "auto" function as I alluded to above. At least with my year model truck I've seen on different forums where the recommendation is not to use the "auto" feature.

I only use 4wheel drive in snow, mud, off-road... not simply on the pavement. Of course around where I live you dont' see snow that often...but one can always drive to locations that have different environments.

Yes... I have the fluid changed in the front and rear differential, the transmission and the transfer-case at regualr intervals.