1968 4x4 short step geared to low

[69GWC]

With 3.08s you will at least be able to use first gear for something other then pulling out tree stumps..lol
Posted via Mobile Device

[possum1]

Originally Posted by 72blazerblue

All I have to say is.....WOWWWWWWWWWW! I love that truck!!!!! That thing is beautiful. Great work, great stance, great color! Very nice. What's the color?

Thank You, I let the boy go through paint chips and pick two colors to take home and try, and this was what he picked, it is called jaspisgruen metallic off of a early 2000's audi. It pops in the sun.

[possum1]

Originally Posted by SS Tim

Really get the numbers for us but look around for swap parts. Depending on what you need and can do as far as gear changes they might not be too far apart in price. Trans vs gears. Deals are out there.

I really do appreciate your help, this is something I don't know squat about. I did every inch of this truck, and it was driving me nuts not to be able to figure this out. I will do my best to get you the info you need Saturday. I figure I won't get the best of both worlds, but hoping for a little of both.

[domeier]

That is an amazingly good looking truck. Dang, I like that paint!

I have 3:73 on my k10, and it screams at anything over 60mph, so I just drive it at 60 and let the stress kings back up behind me. It gets 12 mpg if you baby it, 8 if you drive it like you stole it. It feels just right though, between 0 and 60. Maybe you might want to think about an overdrive trans?

[possum1]

Just took the 68 out on a test run with the tach. She was happiest running in the 50 to 55 range at 2400 and 2600 rpm. There was good throttle response at that rpm and would accelerate from there well going up a hill. I also checked the gear ratio again by turning the wheel twice and it would be in the 4.10/4.11 range.

[MidLifer]

One other thought- if you aren't in love with shifting, you could go to an automatic overdrive trans and keep the 4.11s. Rebuilt GM autos aren't that expensive.

Some day I will do that to my 2wd, probably at the same time I do my LS swap (which will most likely precipitate a change in my marital status).

[possum1]

We talked about doing a automatic, but the boy wants to keep it standard. Guess I raised a good Texas boy!

[possum1]

SS Tim, I just reread and saw that you said something about a baseline mpg. We checked it several times before and 12 mpg is what it seems to get every time.

[SS Tim]

Originally Posted by possum1

Just took the 68 out on a test run with the tach. She was happiest running in the 50 to 55 range at 2400 and 2600 rpm. There was good throttle response at that rpm and would accelerate from there well going up a hill. I also checked the gear ratio again by turning the wheel twice and it would be in the 4.10/4.11 range.

2400/31"/@70mph = 3.16
2500/31"/@70mph = 3.30
2600/31"/@70mph = 3.43
2700/31"/@70mph = 3.56

3.08/31"/@70mph = 2336rpm

3.73/31"/@70mph = 2830rpm
4.11/31"/@70mph = 3118rpm


Here are your numbers. See what kind of deals you can find on ratio sets close to these. But remember the faster you go (the difference between 55 and 70) the more power it will take, so you need to be on the high side if not just above your "sweet spot" for a close approximation. From these numbers, without an actual measured tire diameter or rolling radius, I think it will take smaller tires to keep you happy with 3.08 gears @70+mph IMHO.

Originally Posted by MidLifer

One other thought- if you aren't in love with shifting, you could go to an automatic overdrive trans and keep the 4.11s. Rebuilt GM autos aren't that expensive.
Some day I will do that to my 2wd, probably at the same time I do my LS swap (which will most likely precipitate a change in my marital status).

Not sure what would be involved in mating any automatic to a T-221 transfer case. Off the top of my head I cannot think of any OEM automatic applications much less a GM.

[WIDESIDE72]

Have you considered an NV4500 swap? Only drawback is stock GM t case is deiver side drop vs pass side as needed for 67-72's. Maybe someone with more experience could lend some input. I still wonder why GM did this!
Posted via Mobile Device

[possum1]

Haven't completely finished the first one, but bought number 2 today.

[possum1]

Finally got around to doing the swap. Put 3.73 gears in it. at 75 it was running 3400 rpm. It is definitely in the right direction. We will drive it for a while like this to see if we are happy. If we are I'll do the front. If not, I have a set of 3.42's I'll try next. I also want to get rid of the Rockwell transfer case, to damn loud.

[Spartan]

Like the truck but miss that fender spare. To me that makes a stepper...still tho that's a great color choice.

[burnin oil]

3.73s are a good gear and you should like them alot. When I was high school aged I had a 76 blazer with a 400sb, 4spd and 3.07s. When the motor blew I threw in a malibou wagon 350 and eventually swapped in 3.73 axles. Power was better with the 3.73s and milage was about the same. She will still be spinning the RPM but will easily do the 70 MPH Texas speed limit.

[K10 STEPSIDE]

My truck had a similar setup with a 350 the sm420 trans, t-221 transfer, and 3.73 gears. I would rather turn less Rpms though. I am switching to a 5.3 LM7 and after that gears in the 3.20 to 3.50 range. My sm420 whines some but I have heard they are fairly loud, and have driven other sm465's that where also loud. In the sm420 and I believe also the sm465 1st gear and reverse are unsynchronized making them hard to get in to, so it's best not to get in to a situation where you have to use it. These trans are bullet proof but not freindly.
T-221 is also very difficult to get parts for, if you can prove me wrong I will forever thank you as I need a new side cover and a gasket set.

[2 Far Gone]

I use this when I set up my driveline.

http://www.grimmjeeper.com/gears.html

You can play with the tire size, gear size, transmission and transfer case to get the best numbers for the desired application.

[burnin oil]

Originally Posted by K10 STEPSIDE

My truck had a similar setup with a 350 the sm420 trans, t-221 transfer, and 3.73 gears. I would rather turn less Rpms though. I am switching to a 5.3 LM7 and after that gears in the 3.20 to 3.50 range. My sm420 whines some but I have heard they are fairly loud, and have driven other sm465's that where also loud. In the sm420 and I believe also the sm465 1st gear and reverse are unsynchronized making them hard to get in to, so it's best not to get in to a situation where you have to use it. These trans are bullet proof but not freindly.
T-221 is also very difficult to get parts for, if you can prove me wrong I will forever thank you as I need a new side cover and a gasket set.

Easy to get in gear. Go to second gear then over to first or reverse. If it doesnt want to go in after that just let the clutch out a little and push it back in. Usually just doing second gear will let it fall right in. I used to rock the truck with a SM465 when it was stuck without issues. The 465 is loud because of the gear sets. If you ever pull the top you will see what I mean. Those gears are bigger than a roadranger from a semi, not kidding. Every SM420 I have been around has been louder than a 465.

For the side plate just make your own gasket and plate. When I pulled the PTO off my K20 that is exactly what I did. Made it out of a piece of alum sitting in the shop. It has been on the truck for over a year. I actually do not use the gasket and just put a good RTV sealant on there. Way less leaks from my experience. Same applies for rear ends. If you need a template all you need to do is drain it and clean the surface really good. Let it dry then lay a piece of paper over the hole. Use a #2 pencil to make a shadding and you are good to go.

[possum1]

For the most part We're happy with it, but I think I am going to throw the 3.42's in it just to try it. The truck is turning about 3200 rpm at 70 which is way better but hoping to get it down a little more. If it was a costly swap I would be leaving it with the 3.73's but for the price of the crush sleeve and oil I have to try it. Sometime this week it'll go back on the lift!

[SS Tim]

Good to see some feedback. Are you sure about your rpm numbers? In review you apparently never confirmed the actual diameter (or rolling radius) of your tires. IIRC I deduced them to be 31-32" but your numbers are coming back closer to 29". 3.42 will likely be a good choice but I would still drive around a bit before doing both ends if you are even thinking of trying 3.08 gears or taller tires.