The Stovebolt Site Forums The Parking Lot Big Bolts Overdrive

most of you remember that i have posted other topics on a 63 Cab Over Engine (flat nose) Chevy T60 and now i have another one i still haven't bought the truck yet but i'd like to figure some stuff out before i do anyway... How a hard would it be to add an aux. tranny to this truck it has 5spd tranny with 2spd axle is it possible to do this if so what unit should i look for? and how would i do the shift linkage? or would it just be easier to put in a different trans with more gears and overdrive? if thats better choice also what model should i look for? I'm probly going to end up with a SBC 350 but i have to switch the trans and with the overdrive would drop the rpms alot i might go with diesel (i've coverd that subject also) i might go that route only if i can run 55-60 mph with the stock re-end
thanks
Nate

First, what rear ratio, and tire size do you have?
How fast do you want to go at what engine RPM?

My first thought for a cheap overdrive is to swap the transmission for a Spicer 3053A from a military 2.5 ton. That will give you 0.80 OD. It has a round SAE clutch housing that is #2, but they come with an adapter ring for the larger #1. You probably have a #2 flywheel housing on your engine?

Grigg

the rear end ratio from what i have been told on the old 2 spds is 6.10 and 8.10 and the tire size is 8.25x20 i'd like to be able to run 2,500 rpm at 60 or lower but i'd like to bring it down because at 6.10 gear that 350 will be screamin like a demon at 60 right now the truck has a 409 which the guy is going to keep, but the bell houseing has an adapter plate between it and the engine so it can have a bigger clutch don't know what # it is but is on the those with the adapterring like i said for the bigger clutch
but if i'm switchin the trans and it brings down the rpm enough i might go with a diesel switch also (the good ole sayin go big or go home)

Nate

try this
http://www.drivetraindirect.com/t_gear_calculator.htm
your tire size is about 40"
With a .8 OD it may work. But getting the military trans to fit a regular 350 may be a problem. Unless you can use the flywheel and adapter from the 409 but I doubt it?.

Grigg

with the 6.10 gear .80 OD and 40 in. tire that puts it a hair under 2,500 rpm which i can live with, i'm getting the adapter plate with it and the clutch but the flywheel i'm not positive on but i believe i'm getting all of it just not the engine i know you can get those spicers from boyce equipment but i'm assuming to ship that tranny from utah to minnesota is a bit spendy so does anyone know where to look for that type of tranny in the southern minnesota area

Nate

I guess you need to decide what engine you will run, as that will determine what transmissions will fit easily.
Are you sure the adapter from the 409 will fit the engine you will use? A friend of mine pulled the 409 out of a truck and used it in a car, the adapter stuff allowed the use of a larger flywheel and the starter is mounted to the adapter. Best I could tell the adapter stuff is no good without a 409 or 348 in front of it.

Look on Craigs list and at local surplus places. I have seen the transmissions sell for almost nothing and up to about 200 would be OK, many of the big surplus places ask way to much for them.

Grigg

If you're putting in a 350, you could use the GM S6-650 6-speed manual that they put behind the Chevy Duramax and 8.1L. It has like a 5.75 granny low, and an overdrive of .72. This transmission also has a PTO attach built into it.

Bellhousing is the traditional
Chevy (at least for the 8.1L). This is a high towing capacity trans,,, it gives you the low and the high. I think they go for about $1800 or so new. You could probably pick on up cheaper used though. Actual gear ratios are:

1 2 3 4 5 6 R
5.79 3.31 2.10 1.31 1.00 0.72 5.23

how big of a clutch do those use? sounds like a good idea that i'll have to keep in mind cause with that kind of overdrive that'll give me a low rpm at 60 so it'll work real good and what kind of weight are those actually rated for, probly more then what i'll use but its nice to know and a modern tranny with the pto is an added bonus

Nate

The clutch is 303mm (11.93") and the transmission has a GVW capacity of 12,000lbs and a GCW of 22,000-26,000 lbs. It's a beast.

spicer made 3 auxiliary transmissions for chevys according to the info packet for my 69
7231-a 3 speed .74
6041 4 speed .86
7041 4 speed .83