Rear End Gears and Gas Mileage?

[NickBarrFishing.com]

Hi,

I just bought a 1995 Chevy 2500 with the 6.5 and its a 5 speed with a granny gear, so its really only a 4 speed. I am cruising on the highway at about 1800-1900 RPMS at 55 MPH and 2300 or so at 65.

The guy I bought it from didnt know what the rear end gears were, so I am assuming it has a 4.10 rear end and no overdrive?

Going 65 in a 250 mile trip I got about 16-17 mpg (Estimated with 32 gallon tank.

Thanks,
Nick

 

[Paveltolz]

On Edit:
Welcome to the site and congrats on the find. Your RPMs and mileage are close to what I have with a 4x4 K1500 running 3:73...

Plug your VIN # into this web site and it will decode your truck's original build to include rear end gearing.

http://www.compnine.com/vid.php

Cheers

 

[THEFERMANATOR]

95 will have the NV4500 which is an OD tranny. The tachometers in the 6.5's are known to be off by quite a bit as they are driven by the alternator, and they use a larger pulley than the gassers do. When you get a replacement alternator from most parts stores it will have the gasser pulley and throw the tach off 10% more than it was with the correct pulley. Your milage doesn't sound too bad for a 6.5 with 4.10's if that is what it has. Check your glovebox sticker and see if it says GU6(3.42) GT4(3.73) or GT5(4.10).

 

[NickBarrFishing.com]

I know it has the NV4500, which I have heard is a very strong manual transmission.

The granny gear is real steep. I just start off in 2nd. 1st you can only go about 5MPH in but you could probably pull a house down. I was just thinking it didnt have an OD because of how high my RPMS are at when on the freeway at 65mph.

 

[6.5coalroller]

I got 3.73's and my truck runs around 1500 at 55 and 1650 or 1700 at 60 i wish it was more doesnt have a whole lot of power at 1500 rpms I think it's due to my big tires I got some 33's on it. I recalibrated my vss but it didnt really help with the shift points.

 

[BigBlueChevy]

2300 rpm's at 65 mph is equal to 4.10's as thats usually what I'm spinning every day on my way to work. With 4.10's your mileage is actually pretty good. When i bought my truck she couldn't go past 14mpg, now she does mid 18 with my current mods and doing about 65mph. Just watch out for the winter diesel, it kills your mileage even more :mad2:

 

[Missy Good Wench]

We have two 6.5 powered rigs here (94 Burb 2500 4x4 and the DaHooooley 3500crewcab 4x4)

Both rigs have stock sized tires and 4.10 gears.
On a road trip the Burb will see about 20MPG reliably.
DaHooooley has not been on the road since the rebuild this summer.

Earlier DaHoooley would get around 18-20 Hwy and 17 around town.

I suspect these numbers will go up since the rebuild and fresh injectors and all things being in top condition again.

The 6.5 TD will not do the super MPG numbers that the old 6.2 NA engine would.

If you can get close to 20 your doing fine though.

The pulleys are definately the culprit when it comes to the tach being accurate or not.

I swapped the pulley out on mine and got the proper one back on there.

As was mentioned they get all mixed up and most rebuilts dont have the proper size pulley.

I got mine from a local auto electric shop and he sorted through a box of pulleys and found the right one for me.

The only issue with the pulley size seems to be the accuracy of the tach though.


Missy

 

[mr_goodwrench_06]

Do we know what size pully belongs on there? I know something is off in my truck because it reads around 2000 rpm in 5th at 55mph with 3:42 gears. I'm SURE this is wrong, but I also think my speedo is out...:S

Bill

 

[Big T]

I have 4.10s in a K2500 4wd Suburban. It spins 2200 rpm at 70 mph. I have a replacement alternator from Autozone. On long highway road trips, I get 17 mpg, sometimes close to 18 mpg. I'm running BFG All Terrains in 265 size.

 

[dangerousdave]

2X on Pulley size;
Please, can somebody measure the pulley size on their original or correct alt, outer edge to edge?

Thanx

 

[96 OILBURNER]

There are 2 sizes for the different style alts. One is 57mm and the other is 62mm. Can't rember which is which right now.

 

[DieselCash]

I have 4:10's and almost straight freeway I got 18.6 mpg.

 

[NickBarrFishing.com]

Ok, so I found out I have for sure a 4.10 rear end. Then I am also running 285 tires, which I believe are 31-32 inches tall.

As for the Alternator, It looks like the pulley is pretty small, how much can that affect the RPMS?

Lastly, what is the gas tank in these beasts? 30 something gallons?

 

[Veg_Out]

Nick,

good job on the purchase. You will love it. I'm 450 miles from home and my fuel expense is $0.

 

[mitchedo]

I get right at 15 mpg in my truck at 75-80 mph steady freeway driving. I'd probably get a few more mpg's at 65, but I can't drive 65. ...especially for that 2 hour drive to Dad's cabin. Seems like tach reads about 2500 or so at 75, but I take that with a grain of salt.

I have stock tires and 4.10 gears. I would expect a little more out of a 2wd and manual trans. (Is yours 2wd or 4wd?) However, those bigger tires will eat some mpg, and also show fewer miles than you're actually traveling, thus reducing your calculated mpg even more.

I believe my fuel tank is 33 gal.

Your NV4500 has a .73 overdrive fifth gear if memory serves correctly. 4th gear is direct. Granny gear is 5.60, and is only used for pulling houses and such. 92-94 NV4500's have 6.34 granny gear. I have one of those go go in my Scout some day when I stop spending all my money on this truck.