If I changed this, would I get more MPG?

[Cornfield creations]

My 79 still has the original th350 and NP203, I was thinking about changing out the transfer to a lighter unit like the NP241 with a SYE. Would that shed enough weight to make it worth while? Or would it be best to put in a 700-r4 and the np241? I am getting about 10.5 if I baby it and I hear people getting 15 MPG with 35's, I have 33's and my high gears yet.

 

[BKinzey]

You'll get better gas mileage but not in practical terms. Best bet is the 700 tranny. That will be noticeably better. The 700 should bolt up to the 203 if you use the TH 350 adapter.

 

[jonathon]

It won't really make much of a difference as far as fuel mileage. I also think 15MPG with 35's is a little optimistic.. I'd say 12-13 is good mileage..that's what I get with my 'Burb, hits 10-11 if I'm only driving city or heavy on the throttle.

 

[shaun89]

i think the main thing killing your mileage is your tranny, and the 203,since its fulltime. i have 400hp and my friend has 500hp we both have 208s and they have been fine. just keep it away from the rocks. but id go with a 700r4 and 208. if you want to make a good difference.

 

[kevin400ex]

i ran a t700 in my 79 with a modified 400 small block. on the freeway i saw 15mpg with 4;10 and 35's. i had the lockup converter functional as well and that helped alot too. around town i got 12 all day if i kept my foot outa it. i did however breake the 700 a couple times since my engine wasnt stock.

 

[George_Pimpdaddy]

go the 700r4 and the 241 it has the lowest low range!

 

[Hogback Fabrication]

Dropping ~100 lbs at the transfer case will help a little bit with mileage, but that's probably not worth messing with.

Having fulltime 4WD does, however, take a lot of extra power. Each of your differentials is only ~90% efficient, so you're basically losing close to 10% of your power and mileage by driving that front differential all the time.

Ditching the 203 for a part time case will make the biggest improvement in mileage.

 

[Cornfield creations]

Dropping ~100 lbs at the transfer case will help a little bit with mileage, but that's probably not worth messing with.

Having fulltime 4WD does, however, take a lot of extra power. Each of your differentials is only ~90% efficient, so you're basically losing close to 10% of your power and mileage by driving that front differential all the time.

Ditching the 203 for a part time case will make the biggest improvement in mileage.

Well I have the milemarker part time kit in the 203, sorry I didn't mention that. Gas costs is just starting to be too much. I love my blazer and am trying to find ways of helping it before I have to park it or drive it every once in a great while. The engine in it is still pretty fresh so I am hoping that after it loosens up a bit milage will increase somewhat.