2500 Suburban w/8.1 and 3.73

gtfearons · December 3, 2005

I have a question. I came out of 2001 1500 suburban with the 5.3 litre. Now have the above mentioned suburban and I notice at 70-75 mph when I let off the gas it seems like it is geared lower and slows right down on the highway. The other truck seems to roll a bit easier. The old suburban did not have the trailer package....as I had to add hitch and cooler, I am assuming it had higher gears...and now am I felling the difference in gearing??? Unfortunatley I dont know what gears were in the old truck. At 72 MPH I am turning 2600 RPM, does anyone know if this sounds right? Just want to make sure something isnt wrong......

George

Ape0r · December 3, 2005

My half-ton pickup turns a touch over 2000 at 70 mph with 3.73... the overdrive in the half-ton is .70:1, in the 3/4ths its .75:1... 2600 sounds rather high to me.. that's like what my truck jumps to if it drops to third at 65!

Burbman · December 4, 2005

That's about the RPMs I see on the highway, and I have 4.10's. Yes, the gearing does help with engine braking when you take your foot off the gas. You more than likely had 3.42 gears in your 1500 Sub.

December 4, 2005

I have a question. I came out of 2001 1500 suburban with the 5.3 litre. Now have the above mentioned suburban and I notice at 70-75 mph when I let off the gas it seems like it is geared lower and slows right down on the highway. The other truck seems to roll a bit easier. The old suburban did not have the trailer package....as I had to add hitch and cooler, I am assuming it had higher gears...and now am I felling the difference in gearing??? Unfortunatley I dont know what gears were in the old truck. At 72 MPH I am turning 2600 RPM, does anyone know if this sounds right? Just want to make sure something isnt wrong......
George

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I have 3.73 gears in mine and at 75, I'm running at about 2300-2400 rpms so that sounds about right. Remember this as well, your PCM has the default settings for shift firmness, shift points, torque management and all that other stuff. When you let off the gas, your PCM retards the timing which slows the truck down without applying the brake. After I got my Jesse tune, that's one of the things I noticed right off the bat. When I let off the gas, it just coasts and doesn't seem to slow down as fast as it did without the tune.

gtfearons · December 5, 2005

Thanks all. This help me understand more about the new truck. I also looked today and it is turning closer to 2200 RPMS @ 72 MPH. I appreciate this forum and the things that I am learning.

8.1L · December 6, 2005

I just checked mine today, and at 70, I'm about 2300 rpm. I have the 8.1/3.73, with the trailering package. FWIW, mileage is running 12.5-13 if I cruise and keep my foot mostly out of it...

Jim