M1031 with 4:56 gears, sustable for road/ highway driving?

[Hightechken]

Depends on how fast you like to drive........ As pointed out, 55 is about IT. It is lots more comfortable to go about 45 to 50 with the stock gears and tires.
The stock set up has MORE than enough power! I expect for on road use you could put any gear ratio in you like and still have more than enough power.

 

[highsiera]

also have 4:10 (stock) in my 79 k35. (14bolt rear, d60f) 32"skinny tires, cruises fine at 60-65 even with 4 speed man tranny (low hole). frames rotting so I'm looking for a mashed body m1008, 1025, 1031 etc for a transplant. plans was to keep the 4:10s and swap them in for the 4:56. just my

 

[12vctd]

what motor in that truck thou, you have to remember these guys are wanting to keep thier trucks in a lower rpm range so the 6.2 doesnt come apart

 

[highsiera]

understood, it has a 350 but it was completely choked at the factory. low HP high torque set up. I think the HP is right around 200, it's a 4 bolt main engine, assumably as a blow out preventitive. I hear what your saying.

 

[DrJekl]

The long pole in the tent would be the input shaft on the existing 205 being 32 spline and the 700R output being 27. I believe they did make a 27 spline input version of the 205. Ditch the PTO and run a 208 if you don't run the generator. 700R and 208 combos are cheap and easy to find. Then you have the down shift cable bracket for the 6.2L engine. GM dealers do not have them anymore.

I installed a gear vendor OD unit on mine. Picked one up used for $800 with a 205. Had to build a drive shaft as the GV has the slip yolk on the drive shaft rather than the t-case output.

np205 to 700r4 is a very simple swap. Theres both a spacer or some choose to cut the tailshaft the required amount, or install a new tailshaft. But the spacer (I am having trouble finding in on my pc right this moment) is cheap and works very well. its a 2 inch spacer used to replace a 700r4 with a th350. This is by far the cheapest way to offset the 4.56 gears and as mentioned before with allow a steeper first gear, and od. That with a 33 inch tire you will have gearing to help the 6.2 and have a good cruise speed.

 

[12vctd]

Maybe I wasnt detailed enough. For the 700r4 np205 combo you need a np205 from a th350. Most people sell thier existing th400 np205 combo as they are very popular with the offroad crowd. the brackets I have had great luck sourcing, but i could see where some parts of the country they might be hard to find

 

[jets1959]

I have 255/85r16s on mine and I have no problem keeping up with trafic on the freeway

 

[Matt65]

Mine will run 70 actual, 60 indicated with the 37"s. I generally run about 65 actual for long interstate trips with the 4.56s.

 

[combat jump]

I had my diff gears swapped out from 4.56 to 3.73 by 4 Wheel Parts in San Jose. Also added the slightly larger tires, 285/75. The combo gained me 14 mph at the same rpm. I can cruise in the fast lane now. If you want a completely turn-key increase in top speed, this is it.