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DoobieBrother · 08-08-2007, 01:15 PM

I'm just starting to look at tranny, gearing, etc. and this thread has me wonderin about something. I see you guys talking about high RPM's at highway speeds with gears like 3.73. But I know one two of my current newer vehicles that's not the case.

For example, I have an `03 GMC Sierra (2wd) and a `99 Expedition (4wd). Both have 3.73 gears, and both run 265/70/17 tires. The Expy is turning around 2100rpm at 70 and the GMC is at about 2100 - 2200 or so at 70. When the Sierra had 255/70/16's on it, it was about 2300 at 70mph.

So, why the big difference other than tire size?

08-08-2007, 01:15 PM	#9
DoobieBrother Registered User Join Date: Aug 2006 Location: US Posts: 184	Re: Rear gear?? I'm just starting to look at tranny, gearing, etc. and this thread has me wonderin about something. I see you guys talking about high RPM's at highway speeds with gears like 3.73. But I know one two of my current newer vehicles that's not the case. For example, I have an `03 GMC Sierra (2wd) and a `99 Expedition (4wd). Both have 3.73 gears, and both run 265/70/17 tires. The Expy is turning around 2100rpm at 70 and the GMC is at about 2100 - 2200 or so at 70. When the Sierra had 255/70/16's on it, it was about 2300 at 70mph. So, why the big difference other than tire size? Last edited by DoobieBrother; 08-08-2007 at 01:16 PM.