MPG with 3.73 axle gears

[84CUCV]

The truck has 6.2 400/208 combo. I might be taking out, 4.56 gears and put in rears with 3.73. What kind of MPG will i get? Will i be able to do 70 on the parkway? No sure how to fugure this out on my own. thanks for the help!

Mike

 

[bigblock454]

My K2500 6.2 Burb with a th400, 3.73s and 31s could get 19 MPG if kept around 65. It would do 75 or 80 maybe but sure screamed down the road.

 

[84CUCV]

OK thanks mike

 

[Pookster]

it will do it, but I dont think you'll see the fuel economy that your looking for. Take it down a few notches to 55, then you'll see 20+ . /forums/images/graemlins/smile.gif

Leave the 456 in, put in 33 or 35" tires. /forums/images/graemlins/smile.gif

 

[84CUCV]

that one thing i never thought of. thanks

 

[rjfguitar]

With 4.56's, 31's and a non OD tranny you would be turning 3,213 RPM's at 65mph.

With 3.73's and the same combo you would be turning 2,628 RPM's at 65mph.

With your current 4.56's and you step up to a 35" tire... 2,845RPM's at 65mph.

For the best fuel mileage you want to be around 2,000RPM's. I get 20+ at 70mph turning 1,800 RPM's with 3.54 gears and true 31's on my Dodge cummins.

I would consider a taller tire for the cheapest route but if you really want to get the best mileage you should consider swapping to a Th700R4 or NV4500. The first gen dodge cummins 89-92 had the option of a 5 spd manual and a torquer flight 929. You got 4.10's behind the 5 spd and 3.07's behind the 3spd auto. THe clear choice is the manual but the problem was that it wasn't an NV4500 yet but a underrated LD tranny that had many problems. The TF auto worked fairly well but the high gears hurt acceleration and towing performance.

My point is is you could gear way up but with slower acceleration as a consequince. IMHO, an OD tranny is the way to go.

 

[jac6695]

[ QUOTE ]
torquer flight 929

[/ QUOTE ]

/forums/images/graemlins/thinking.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/histerical.gif

 

[84CUCV]

OK know a good shop for 700r4s? thanks

 

[rjfguitar]

[ QUOTE ]
OK know a good shop for 700r4s? thanks

[/ QUOTE ] Yes, the custom shop that built mine.....but you are in NJ and I'm in Cali. /forums/images/graemlins/smile.gif Bowtie OD builds a nice 700...

 

[rjfguitar]

[ QUOTE ]
[ QUOTE ]
torquer flight 929

[/ QUOTE ]

/forums/images/graemlins/thinking.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/histerical.gif

[/ QUOTE ] /forums/images/graemlins/confused.gif /forums/images/graemlins/dunno.gif

 

[jac6695]

I do it too: should be Torqueflite 727 /forums/images/graemlins/deal.gif

 

[84CUCV]

Thanks i will check it out. mike

 

[rjfguitar]

[ QUOTE ]
I do it too: should be Torqueflite 727 /forums/images/graemlins/deal.gif

[/ QUOTE ]IIRC there was the TF727 and heavy 929 model.

 

[imiceman44]

[ QUOTE ]
[ QUOTE ]
I do it too: should be Torqueflite 727 /forums/images/graemlins/deal.gif

[/ QUOTE ]IIRC there was the TF727 and heavy 929 model.

[/ QUOTE ]

The Torqueflite 727 was the heavy duty.
The 999 is the other one you are looking for.
They also have a 904 light duty.
I can't remember if the 999 was an OD or the 904 but the 727 was not.