2006 Silverado doesn't hold speed when gearing down...

[Jamilz28]

I have a 2006 Silverado 1500 with the 5.3 and I do a lot of skiing so I drive up and down the mountain a lot in the winter. Driving downhill I gear down usually into 2nd or 3rd, but it doesn't do much to slow the truck or hold speed. Gearing down will momentarily slow the truck, but seconds later it will continue to free roll and pick up speed while the rpms increase. I have to use the brakes just as much when geared down as when I'm just in drive. If I don't use the brakes, it will continue to accelerate up to 100 kms even in second gear. The drive down the mountain is super hard on the brakes, so I'd like to avoid using them as much as I can. I always figured that gearing down would maintain speed on downhill grades, but it just doesn't. My previous GM truck did the same thing. Does gearing down in any automatic not do anything when going downhill? Or is it just these trucks?

Edited November 24, 2020 by Jamilz28

[Jamilz28]

Anyone? What I mean to say is that even when gearing down the truck just coasts and continues to pick up speed and the RPMs will run up to like 4000. I have to just end up braking or I'll be moving too fast. Setting a desired speed on cruise control doesn't hold when driving downhill either.

[CamGTP]

If the grade is steep enough the engine braking probably won't be enough to hold it back.

 

That truck is old enough that it doesn't have an actual grade braking feature in it. It's possible that putting it into a tow/haul mode will make it better but I don't know if it will.

[Jamilz28]

I got your reply while on a beer run and I decided to take the long way home into the bottom of the valley to test your recommendation. The grade was about -35% for over a kilometer. I put the truck into tow/haul mode, shifted into second gear when I reached 60 km/h, and then truck maintained that speed all the way down. So, I can confirm that tow/haul mode works or at least helps. Thank you very much for your reply! This is going to save my brakes this winter!