Tow/Haul mode

[bjpsg]

I have 2000 silverado trans. works fine out of tow/haul
In t/h it shifts fine but when you let off the gas the engine dosen't
hold back . any thoughts!!!!!!!!!!
bjpsg.

[desertmike1]

If you have a C1500 with a Hydramatic trans, this sounds normal.
I have a C1500 with a 5.3 and when I let up in tow/haul mine will up-shift until I gain about 5MPH then it will down-shift.
Does this sound like your's?

[fabrikator]

My '99 1500 does the same as DESERTMIKE1's, if that's what you're referring to.

I think the objective of the T/H Mode is to keep the RPMs at an optimal level for the speed you're traveling/terrain- a balance between gas milage and towing/hauling capability.

I've recently been hauling various weight trailers in T/H mode and it seems to run about 2200-2400 @ roughly 60 MPH. Run up above 65 MPH and level off the RPMs (back off from acceleration) on level highway and the tranny kicks into a higher gear helping gas milage. When I get to a hill and press the accelerator to maintain speed, the trans will kick down to a lower gear for the extra power.

[rgarboss76]

Not being a smart ass but in the owners manual you shouldnt be using tow haul unless your towing over six thousand pounds. It will tear up your tranny. If your towing under 6000 just tow in D range not overdrive range for that will tear up your clutchs.

[bjpsg]

Originally Posted by desertmike1

If you have a C1500 with a Hydramatic trans, this sounds normal.
I have a C1500 with a 5.3 and when I let up in tow/haul mine will up-shift until I gain about 5MPH then it will down-shift.
Does this sound like your's?

Thanks for the reply,
Let me see if I can explain better, let's say i was running 60 mph at
2200 rpm and let off the gas ,as it slows to 55 the rpm would drop accordingly say 1800 rpm.
With mine in tow/haul mode when I let off the gas at 60 mph and the rpm at 2200 the rpm's drop to 1200 rpm's just like a straight drive with the clutch pressed in. Out of tow/haul mode it works fine,I bought my 2000 silverado used and use it to pull a 7600 lb. camper.
I just use it out of tow/haul mode and leave it out of over drive.
The trans, fluid & filter has been changed with no trash or metal in it.
Thought it might be a sensor or something.
THX.

[fabrikator]

BJPSG: Again I'd have to think that the trans is selecting the optimal RPM range for T/H mode. The sudden decline in RPM (down to 1200) could be a way to scrub off extra speed by using the engine as a brake a little more than normal. This would be most effective in a loaded situation and/or in a down hill decent and would save your brakes with that big camper behind you.

Maybe someone else has another idea as to why your trans is doing what it is. In the meantime, I'm going to keep an eye on mine when decellerating in different modes to see what the differences are in RPM and compare them to yours.

RGARBOSS76: I'm not exactly sure your manual and mine are the same then.

1999 Silverado (all models) Manual (*1) states "Tow/Haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of the vehicle's Gross Combined Weight Rating (GCWR)." Also that "Operating the vehicle in tow/haul when lightly loaded or with no trailer at all will not cause damage." Though it also goes on to state the obvious- it's recommended use is only with heavy loads. You'd have to do the math on your model then decide how close you are to the 75% (if not over) to determine the "effectiveness" of the T/H feature.

(*1: C9915 A First Edition- General Motors Corp.)