Picked up my one tons this week, geared 3.73. The plan is 7-8 inches of lift and 37" military oz hummer tires. Will I have enough gear to spin the 37's off road and maintain a decent cruising rpm @ 65mph. 700r4 tranny, np241 transfer case. A gearing calculator I found puts the rpms in the low to mid 1500's @ 65mph w/ both stock 3.08 gears and 31's, and 3.73 gears and 37's. May add a th400 and np205 sooner or later. Thanks for any input, it sounds good to me, but just wanted a little conformation...Dave
CK5
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Gear ratio for 6.2
- Thread starter medicdave
- Start date
Wrench
1/2 ton status
1500's is definitely on the low side for highway cruising even, optimum RPM band for the 6.2 is up around 1800-2100.
MaxPF
1/2 ton status
4.56's are the sweet gear for a 6.2, OD tranny and 37's.
If you are set on going to a TH400, plan around that. You will be ok on the highway with the 3.73's without OD, but your around town power is going to be poor. Mileage will also suffer since the motor is going to be constantly straining.
4.56 gears would be ideal around town and offroad, but highway cruising will be impacted.
You are looking for the best compramise by loosing the OD. Do you want highway speeds or offroad performance the most?
4.56 gears would be ideal around town and offroad, but highway cruising will be impacted.
You are looking for the best compramise by loosing the OD. Do you want highway speeds or offroad performance the most?
MaxPF
1/2 ton status
The best compromise is no compromise. Simple answer: 4L80E
That would be the best answer... you just need to find a 1991 V2500 Suburban or Crewcab with a 6.2L as a donor. It is the only year with the stand alone transmission computer that fits perfectly into the 73-87/91 body.
MaxPF
1/2 ton status
I've ran 35's, 38's (13/38 TSLs, more like a 37), and 39.5s with 4.10 gears and the 700r4. It felt good with 35's, but OD was worthless as soon as it got the 38s (again, on the short side). With 37s and 3.73 you would have to keep in in D/3rd on the highway so I don't think it would pull OD the majority of the time. Another guy in our club recently built a CUCV with 36's, 3.73 gears, and a TH400 and it cruises nice on the road.
I've got 38's, 4.56's, and a TH400 and it needs an overdrive. I know a guy on another site who swapped a TH700R4 into his M1008 and he loves it with his 38's and 4.56's.
Huffed Blazer
1/2 ton status
I was running 35's on the truck with 4.11's and switched to 33's. I need to put a tach in soon, but it feels a little better with 33's.
Diesel or gas?
33" tires, 4.10 gears with a 6.2L and SM465 is a great combo for towing power. But freeway speeds are a problem.
Huffed Blazer
1/2 ton status
Sorry. It's a diesel.
Then going to 33's should make it feel worse. The smaller tires are making it rev more and operating out of it's power band with those 4.10 gears.
Actually it will be the opposite, until you get above 55-60 mph. Everything below 55 will make better use of the diesel's power band. With such a narrow power band and no over drive though you are trying to decide on what to compromise on. You can either get great power at slower speeds or better highway cruising and poor power around town.
Huffed Blazer
1/2 ton status
That's how my blazer felt. 35's were good for 70 mph, but a little lackluster around town. The 33's are a LOT better around town, but she feels like it's revin' higher than I wanted on the highway. Of course mine's an 700r4. Time for a tach. Maybe today.
mill5471
1/2 ton status
Just to put out some more info on the subject. I have an 85' 1-ton, single rear wheels, 6.2 diesel with the th400 and 4.10 gears. It had 235/85-16 on it, which i belive is around 30". I put 285/75-16 on it ( 32" 
)and i could definetly tell a difference with the motor turning less rpm's at highway speeds, i don't really feel a difference around town. My "highway" speeds are 55-60 mph, haven't had the chance to take on on the express way but i think it would be turning to many rpm's at anything over 60-65 mph. 55 mph seems to be the sweet spot with my set up which is fine until i want to go up north. Makes for a long trip not going on the expressway.
)and i could definetly tell a difference with the motor turning less rpm's at highway speeds, i don't really feel a difference around town. My "highway" speeds are 55-60 mph, haven't had the chance to take on on the express way but i think it would be turning to many rpm's at anything over 60-65 mph. 55 mph seems to be the sweet spot with my set up which is fine until i want to go up north. Makes for a long trip not going on the expressway.
