3.73->4.56 Regear Results
Regeared my truck a few weeks ago.
I thought I would start a thread to let people thinking of doing the same what to expect. I've definitely seen the question asked a few times in the past, and on every forum I've been a member of the usual response is:
"You'll shoot your eye out kid" or something along those lines.
The truck we started with was an 136K mile 1996 Suburban K1500 5.7 Vortec.
It has the tow package, so it already came with an external cooler, 3.73 gears, and larger rear brake drums.
I've already upgraded the brake master cylinder to a 2001 model, and installed 3/4 ton calipers. Also has 17" wheels with E-range tires from a new Nissan Titan. Also has helper springs in the back.
We tow a 2015 Starcraft 239TBS, 5200 "dry" on the yellow sticker, 6500lbs GVWR. Not huge for most people but plenty for this old half ton.
When the axle seals went, repeatedly, I decided it was time for new axles and a regear.
We installed 4.56 gears and I had the computer retuned for the new gear ratio.
After the gears, it cruised at about 2200rpm in OD at 65mph, with 31.5" tires.
PERFORMANCE
Tows great, big improvement. Before the gears, OD was useless. It would unlock the converter or downshift at the slightest slope or gust of wind.
Now, it will stay firmly locked in OD for most hills. A downshift to 3rd was enough for MOST steeper hills. On our test trip, we did a ~2700 down through NC, TN, GA, then back up to DE Via the Chesapeake Bay Bridge.
We did hit a few hills in TN/NC on RT26 that required 2nd gear...I looked them up later at they were an 11% slope. Not sure what that is in grade.
It did get hot (230F) on those climbs, with 90+ air temps and the AC running on max. I will be addressing the cooling system next to fix that.
FUEL ECONOMY
First two legs of the trip, with the hills, resulted in 8.9mpg and 8.5mpg. My normal mpg on flatter trips has been a BEST of 8mpg. So even with what most would consider crazy 4.56 gears on almost stock size tires, I gained MPG towing in worse conditions. Not sure about unloaded mileage because I mostly use this truck for the camper.
I will try to get some flat land towing numbers this weekend, if I bother to refill the truck when we get home.
Overall, I am very happy with the regear. No power mods I could have done would have resulted in this much improvement. The cruising RPM doesn't bother me, it is smooth and quiet at 2200 with plenty of passing power.
I thought I would start a thread to let people thinking of doing the same what to expect. I've definitely seen the question asked a few times in the past, and on every forum I've been a member of the usual response is:
"You'll shoot your eye out kid" or something along those lines.
The truck we started with was an 136K mile 1996 Suburban K1500 5.7 Vortec.
It has the tow package, so it already came with an external cooler, 3.73 gears, and larger rear brake drums.
I've already upgraded the brake master cylinder to a 2001 model, and installed 3/4 ton calipers. Also has 17" wheels with E-range tires from a new Nissan Titan. Also has helper springs in the back.
We tow a 2015 Starcraft 239TBS, 5200 "dry" on the yellow sticker, 6500lbs GVWR. Not huge for most people but plenty for this old half ton.
When the axle seals went, repeatedly, I decided it was time for new axles and a regear.
We installed 4.56 gears and I had the computer retuned for the new gear ratio.
After the gears, it cruised at about 2200rpm in OD at 65mph, with 31.5" tires.
PERFORMANCE
Tows great, big improvement. Before the gears, OD was useless. It would unlock the converter or downshift at the slightest slope or gust of wind.
Now, it will stay firmly locked in OD for most hills. A downshift to 3rd was enough for MOST steeper hills. On our test trip, we did a ~2700 down through NC, TN, GA, then back up to DE Via the Chesapeake Bay Bridge.
We did hit a few hills in TN/NC on RT26 that required 2nd gear...I looked them up later at they were an 11% slope. Not sure what that is in grade.
It did get hot (230F) on those climbs, with 90+ air temps and the AC running on max. I will be addressing the cooling system next to fix that.
FUEL ECONOMY
First two legs of the trip, with the hills, resulted in 8.9mpg and 8.5mpg. My normal mpg on flatter trips has been a BEST of 8mpg. So even with what most would consider crazy 4.56 gears on almost stock size tires, I gained MPG towing in worse conditions. Not sure about unloaded mileage because I mostly use this truck for the camper.
I will try to get some flat land towing numbers this weekend, if I bother to refill the truck when we get home.
Overall, I am very happy with the regear. No power mods I could have done would have resulted in this much improvement. The cruising RPM doesn't bother me, it is smooth and quiet at 2200 with plenty of passing power.
