Which NV4500 Gearing to Use?

[argonaut]

I have two GM NV4500 transmissions. The first is a 94 with lower, slightly wider spread gearing. The second is a 95 with higher, more closely spread gearing.
Both need new mainshaft and the chosen one will also be getting a general rebuild with bearings, syncros and seals.

My question to you, forum, is which would be best to put into my 66 Short K20? Truck weight is about 5,100lbs wet (sans driver ), has 4.11 diff gears and 35" tires, powered by a fresh, stock 402. Intended use is partly around town, partly fire roads and light rocks, mud, general rough terrain getting to back country. This is not a rock crawler, mud bogger, etc.

94 NV4500
1--6.34
2--3.44
3--1.71
4--1.00
5--0.73
R--6.34

95 NV4500
1--5.61
2--3.04
3--1.67
4--1.00
5--0.75
R--5.61

Any input is welcome!

[argonaut]

Maybe I should add that it has an SM465 in it now, backed by an NP205. 2nd gear is fine taking off but the gears are a little too far apart. I get a solid 10mpg on the highway w/o overdrive.

[83GMCK2500]

Sounds familiar...my '83 has a 465, 208, and 4.10s, 10mpg hurts. I picked up a '93 NV-4500 and I'm resealing and installing new syncros as well. Please please please, do not use any other oil than the factory spec'd Castrol Syn-Torq, those danged syncros will not last with anything else in there.

I, too, had my choice of higher or lower geared. I went lower geared because it was closer to the 465 which I appreciate the deep first in. Also, given that you have a 205 I would definitely go with the early 4500. If I remember, the 205 has a so-so low range and if you're ever in a position where you need the low gear it'd be good to have it.

Are you aware that your '95 NV-4500 is a one-year-only configuration? Upgraded top cover, higher low gear, but early external slave/throw-out bellhousing with the front bolt pattern of the 93-94 NV-4500s. Odd one indeed...

[argonaut]

I actually think that 10mpg isn't so bad for a two and a half ton tank with large heavy tires. I have steelies with toyos which is about as heavy as it gets for radial 35"s.
I'm hoping for 13th with the OD.

I know that DirtyLarry is running the later gearing in his pickup but he also has that huge fuel injected 8.1L which makes my 42 year old 6.6L look like a little weenie.

[ryanroo]

having driven trucks that have had both styles, i would run the higher first and reverse truck. my jeep has an early lower style and i never need first. even in the mountains. its always low range and 2nd or 3rd. the slightly higher first rarely affected me when i had that truck, but you notice it if you are backing up. the lower reverse makes the truck painfully slow. the better gear split is nice too. i have driven both styles with a big block and both with a small block and you don't really feel feel much difference taking off.

[argonaut]

That is great feedback guys!

[argonaut]

Ryan, i know Jeeps are pretty light. Were any of these test drives in big heavy trucks? I also do a little towing and hauling.

[doubleclucker]

argonaut-I done the swap and I waited long time to find the 5.61 first gear trans from a 95' . My truck had the muncie also and i can tell you the spacing from 2 to 3 gear is so much better now; and the first gear is not as low as the muncie's (6.54) but is a little more usuable on the street and could get away with a little more higher if they made one , as now you almost have to use that gear to start from a stop or use more clutch with 2nd. Though towing, this first gear is perfect for starts with alot of weight on.
The O/D 5th gear is the clincher thouigh 600 Rpm drop in that gear-
I can now go faster to keep up with traffic and spin lower RPM then ever
"win win in my eyes."
I swapped it in and i am not looking back!

[argonaut]

Clucker,
wow, so you are saying that with the higher gearing you now actually utilize first/low gear when accelerating from a stop on the street (unladen)?

[doubleclucker]

Originally Posted by argonaut

Clucker,
wow, so you are saying that with the higher gearing you now actually utilize first/low gear when accelerating from a stop on the street (unladen)?

I use 1st gear whenever moving from a dead stop as you will notice
2nd gear in the 95'-up trans is alot higher (3.04) than the early nv4500 (3.44) or also the muncie 1st or whatever you want call it at (3.58) and if you use this gear to start as I said earlier you will need to use more clutch to get going.
couple pics off this site.

[ryanroo]

Originally Posted by argonaut

Ryan, i know Jeeps are pretty light. Were any of these test drives in big heavy trucks? I also do a little towing and hauling.

All of the trucks ive had these in were fullsize. my jeep is a M715. basically an uglier version of the J20. it weighs in around 6k. all the other trucks were GMT400s either 2500 or 3500s with the exception of the 72 k2500 i swapped one in.

i will add that i have always used the 2nd forward gear to start with no load. its never been an issue for me slipping the clutch more. in both big and small block trucks.