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 > Coast on the uphills accelerate on the downhills

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badsix

north bend or.

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Posted: 01/15/20 11:12am Link  |  Quote  |  Print  |  Notify Moderator

ppine wrote:

I can't agree with your technique at all. There is an rpm range that all engines pull best in. That is where you want to be. Gearing down and going slower will produce less heat.


Yep ^^^ also trying to keep you converter locked is going to burn it up not designed to pull a 7000 or more T/T up a steep grade. only for hi gear and not pulling, luging the trans will heat it more. that's why transmissions have gears the more the better. let it shift down and keep the engine in the rpm range that makes the most power. big rig drivers don't lug there engines they run them at a certain rpm range for the best power range and adjust with there gear boxes.
Jay D.

Groover

Pulaski, TN

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Posted: 01/23/20 11:58am Link  |  Quote  |  Print  |  Notify Moderator

Have you thought about cleaning the existing transmission cooler and radiator? Even though you can't see it there may be a surprising amount of dirt lodged in them.

PatJ

Eastern WA

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Posted: 02/02/20 09:05pm Link  |  Quote  |  Print  |  Notify Moderator

Wondering what you learned here? Did you pull lower hose and look at in rad heat exchanger?


Patrick

opnspaces

San Diego Ca

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Posted: 02/03/20 01:08am Link  |  Quote  |  Print  |  Notify Moderator

Groover wrote:

Have you thought about cleaning the existing transmission cooler and radiator? Even though you can't see it there may be a surprising amount of dirt lodged in them.


Yes I hosed them out with copious amounts of high pressure water from the garden hose. The radiator is brand new so but I hosed everything out anyway. Unfortunately it made no difference.


2001 Suburban 4x4. 6.0L, 4.10 3/4 ton
2005 Jayco Jay Flight 27BH
1986 Coleman Columbia Popup.

opnspaces

San Diego Ca

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Posted: 02/03/20 01:28am Link  |  Quote  |  Print  |  Notify Moderator

PatJ wrote:

Wondering what you learned here? Did you pull lower hose and look at in rad heat exchanger?


Thanks for checking back. No I haven't had a chance to pull the hose yet. But the drive home from the desert this morning convinced me that I need to do it sooner rather than later. The biggest problem is I haven't found a drain **** on the radiator and I don't want gallons of antifreeze hitting the driveway from just pulling the lower hose.

So in the interim I rigged up a poor mans cooler to keep the heat down while I try to save up some money for the inevitable parts swap. My son's car was headed to the junk yard so I pulled the windshield washer jug and tubing out if it before sending it on it's way. I mounted the jug under the hood of the Suburban and ran a line up to a patio mister pointed across the transmission cooler. While it's not perfect,(okay yes it is really redneck) it does keep the temps from hitting the red zone.

parker.rowe

Delaware

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Posted: 02/07/20 06:19am Link  |  Quote  |  Print  |  Notify Moderator

Great thread.

Just to add more real world experience, my old 96 burb, similar to your old one, never exceeded 200F trans temp pulling hills. It had the factory external trans cooler and the in radiator one in series. Same trailer as in my signature.

It would lock up in third, and OD, although when pulling it was always in 3rd. It would not hold OD at all with the factory 3.73 gears. My camper is very similar in weight to yours...slightly heavier when we are loaded up.

When going up hills, I would try to ride the converter as much as I could, keeping it locked while in third gear...however some hills required 2nd gear with my foot to the floor. No lockup there.

Our new suburban has a 4l80, which also locks up in 3rd. You have to be over a certain speed and under a certain % of throttle position for it to do so (just like the old 4l60).

I'm not 100% on the criteria for the gmt800 trucks, but I was under the impression that in tow/haul it would try to keep the converter locked longer. Forcing it into 3rd might not be needed, but it should not prevent the convertor from locking up.

If the computer was commanding lockup, and not getting it, you would get a check engine light.

I agree with everyone, you truck, with 4.10s and a 6.0, should have no issues with that camper. Sounds like an inspection of the cooling system is in order.

How big is your factory external cooler? I would service the transmission, after heating the fluid up like that a few times. Check that fan clutch too. It doesn't make sense since the engine stays cool, but installing and HD clutch in my old truck made a noticeable difference, even though the old one seemed good.

Love these suburbans, our old half ton was a great truck. But once we started doing long 2-3k trips and hitting steeper grades, I was worried about sending it to an earlier grave.

So we sold it and got our "new to us" 2500 burb like you did (I've always wanted a big block suburban), and unfortunately have to work out all the kinks we already addressed in the first truck. But I think it will be worth it in the end.


2015 Starcraft TravelStar 239TBS 6500 GVWR
1997 GMC Suburban K2500 7.4 Vortec/4.10
1977 Kawasaki KZ1000


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