Tires and Gears

[WFO4X4]

i know there is a way to fab a 1ton IFS front into a 1/2 ton, but it aint easy.....

 

[Blue95]

A Turbo 400 is a 3 speed tranny correct? so that needs to be taken into account, 5.13's and a 3 speed tranny is not going to be good to drive on the road even with 37's

 

[Solid94]

Actually with a turbo 400 you would have a stronger trany that will hold up to larger tires the only downfall is no overdrive. So you will be around 2,500-3,000 rpm at about 65-70 mph. I almost went that route with my truck but to rebuild it and get only a 1 year warranty vs the 3 year warranty I got from GM

 

[Blue95]

I know they are very strong, but that is what these guys are not realizing is that if he is going to drive this on the street or interstate a speed tranny, 4.88's or 5.13's, and 37's is going to be over 3000 doing 65-70 or more and that is not good at all.

 

[4x4incountryboy]

the transmission now has a shiftkit in it, I know it has nothing to do with RPM and speed but its a nice benefit to know its a little stronger. and blue95, wouldnt 4.88 be no different then when my truck had 31s with my 3.73s? it was my understanding that it was near the same porportions, I may be wrong though

 

[Blue95]

I am not sure of the correlation, but with a turbo 400, 37" tires:

RPMs at 65 with 4.88 are: 2900 RPM

RPMs at 65 with 5.13 are: 3030 RPM

RPMs at 70 with 4.88 are: 3120 RPM

RPMs at 70 with 5.13 are: 3260 RPM

EDIT: so what I am trying to say here is if you want to drive this truck to town or down the interstate to a show or to a mud event, then that high of gear is not going to be good with 37's. IF you want driveability you are going to have to give up a lower gear ratio so you are not turning that engine at 3000 RPM, it will not last long or like you, but love the gas station.

 

[4x4incountryboy]

2900rpms arent that high in my mind...I have an 84 corvette with a 4speed tranny in it, standard, and that is close to what it turns without overdrive...I might be wrong ....what are the rpms for a turbo 400 with 3.73 and 31 inch tires?

 

[Blue95]

with that combo running 2900RPM you would be doing 71 MPH. That is your call, I know I would not want to turn my engine in my truck that fast cruisng down the interstate for any longer then a few miles, but if you are ok with it then go for it, I am just posting facts so you can make an informed decision.

 

[am92]

Didn't think about him having a 3 speed tranny...in that case I would go with 4.56 to hold the rpms down a bit when highway cruising

 

[4x4incountryboy]

I by all means dont want to open the engine up to 2900rpms for a long period it sucks fuel now as it is without any load. Alot of my friends stick with 4.10s in thier 10 bolt and have no issues. Looking back at the gear ratio calculator, 3.73s with 31s would almost be the same be it a 4.56 with 37s both doing 70. My only option for solving any sory of high rpms at 70mph would be to find a tranny with autodrive with low miles or convert it to a 5 speed stick, which at this point in my build would not be all that hard