3.73 vs 4.10 th400

[welpro222]

What do you guys think? 3.73 or 4.10 for my 87 suburban 6.2 th400 with 33 inch tires. At the moment I have 3.73 in it and I see no problems. I have a dana 60 and 14 bolt ff rear with 4.10s that im rebuilding to go into my suburban, I'm still trying to decide whether 3.73 or 4.10 would be good for me. Would the mileage lost be bad going from 3.73 to 4.10? Is cruising at 2500 rpms bad for the 6.2?

Use for vehicle:

Occasional Towing
Camping, driving on mostly logging roads
Hunting

 

[Drock]

I used this rpm calculator and it said the 4.10's would put you at 3000RPM's at 70MPH...Here's the linkhttp://www.ringpinion.com/Calculators/Calc_RPM.aspx

 

[FMJ]

3:73's, 4:10's = Higher RPM = crappier mileage. I have a 14 bolt with 3:73's in my 1009 I get about 13-14 MPG @ 70 mph

 

[Skinny]

Are they already set up for the 4.10's? If you have to buy new gears, install kits, and setup bits plus labor, that is ballpark for an OD trans. I'd rather have a 700r4 with the 4.10's already in the axles than a TH400 and 3.73's.

What do you have for parts already?

 

[welpro222]

I am getting ready to reinstall the carriers in both axles. I have the 3.73 for the rear only and I have the 4.10 gears for both axles.

 

[welpro222]

I do not see a 700r4 in my future. I may get 37 inch tires later on. This is not my DD, but I do not want to to loose 5 mpg by going to 4.10 gears.

Plus when I'm cruising on the freeway, im only going 60 mph max.

 

[Bunkerbuilder]

Here is a rpm / mph / tire / etc calculator for your and everyone elses perusal.
It also can factor in a od transmission.. If you ever consider going in that direction.

Im in the middle of putting a NV4500 backed by a NP205 6 bolt round input face. This way I wont have to mess with the differentials and ill have plenty of pulling power when I need it but also highway speeds with the OD.



http://www.novak-adapt.com/knowledge/gearing.htm

 

[richingalveston]

if you plan to go with 37's in the future, put the 4.10 in. 33's are about as big as you want to go with 3.73's and it will probably feel some power loss at lower rpms.

my blazer was a dog with 33's on it and a suburban is a lot heavier. If all you ever do is 60 mph then the 4.10s won't hurt you and they will be much better when pulling a trailer.

spend your money on a good front locker.

 

[welpro222]

I'm going to be putting a dana power lok in it, since I already have it. I'm thinking of a grizzly locker in the rear.

 

[acesneights1]

I had an 83 K20 with a 6.2/TH400 33's. It was originally 4.10. A swap to 3.73s made it much more drivable.

 

[rchalmers3]

Use for vehicle:

Occasional Towing
Camping, driving on mostly logging roads
Hunting

Given your intended usage, I wonder why mileage is a concern. It may be best to consider how you might select gearing for obtaining the best part of the torque curve at the speeds you expect to drive at and let the mileage fall where it may.

Towing, driving on logging roads and seeking out a camping site all sound like relatively low speed operations (40-50 mph). If so, I'd choose gearing that will put you at max torque (it's about 1500-1800 rpm) @ 45 mph.

This is just a suggestion. You may have better ideas about your anticipated speed ranges, and can make better calculations based on your knowledge. As they say, "your mileage may vary!"

Rick

 

[welpro222]

I think I will stick with the 4.10 gearing, because I may put my 37" humvee tires on it.