I have a GMC Suburban and have a tranny question. I was under the impression that so long as the tranny wasn't shifting up and down to maintain a speed over hills (i.e. maintain speed with cruise control set), that my transmission wouldn't be harmed.
My question really seems to be about 'passing gear'. During this past weekend, I was going through a mountain pass, held it in overdrive (in passing gear) throughout this ordeal. I was traveling 60mph in OD and in passing gear, at 2300 RPM, the temp gauge looked great and it was "steady as she goes" through this mountain pass area. On the way home on the other hand, and for the same hills, I down shifted to 3rd gear and was holding a steady 55mph at the same engine RPM but the engine was running hotter. Interesting to note too, that on the way over the first time while in OD passing gear, for the same RPM my speed was higher.
In short - isn't overdrive passing gear the same as running in 3rd gear? I always heard it was but thought I'd try putting it into 3rd gear on the way home and was surprised to see the same engine RPM with a lower speed and a hotter running engine (as per my temp gauge).
Anyone have info on this? I guess my question is, isn't overdrive passing gear the same as 3rd gear??? If this assumption is correct, nothing should happen when I'm in overdrive passing gear on a mountain pass and pull the transmission lever into 3rd gear.
TIA for any info on this...
John