What 3 speed manual came In a square body?

[Ypsik10]

My local junkyard has large flatbed dually with a 3 speed manual are they worth anything ? Is this something could use if I wZnted to covert to manual?

 

[1987 GMC Jimmy]

They just came with a column shifted Saginaw three speed. From what I understand, they're not the toughest. If it came out of a square, I'd get the column, too. Plenty tough for a six cylinder and even a 305, but I would do something else for anything bigger. There's a New Process A833 four speed overdrive gearbox that would be cool if you could find all the parts you need. More feasible are an SM465 or NV3500/4500.

 

[Ypsik10]

This truck has a manual 3 speed floor shift. AtleAst that's what the knob indicated before somone got it.

 

[1987 GMC Jimmy]

I don't know about that. The SM465 is a functional three speed with an 'L' speed for crawling, but that's the closest it comes as far as I know.

 

[RetroC10Sport]

Being a dually, it had an SM465.

 

[Ypsik10]

Ok so this is something I could put in my truck and still cruise the freeway (65) like my turbo 400..

 

[WFO]

Ok so this is something I could put in my truck and still cruise the freeway (65) like my turbo 400..

It would have the same 1:1 ratio in high gear as your turbo 400.

 

[Keith Seymore]

It would have the same 1:1 ratio in high gear as your turbo 400.

...but has a "creeper" low gear. It's 6.22:1 if memory serves.

K

 

[vkh]

Actually would take slightly less rpm than the th400 since you wouldn't have any converter slippage.

 

[MikeB]

The 3-speed Saginaws came with 4 sets of ratios. The three I'm familiar with are these:

3.50 low gear used with the 250-six.
2.85 low gear used with 305 and 292.
2.54 low gear used with the 350.

2nd gear, of course, was different for each trans.

The transmissions were all the same other than gear ratios. Obviously the one with a 2.54 low gear could handle more engine torque due to generating less torque multiplication. A 350 engine would easily break a trans with a 3.50 ratio.

Lots of very bad info about these transmission on the Internet, mostly people not realizing there were several ratios used behind various engine sizes. The trans with 3.50 low gear was probably rated at no more than 220 lb/ft torque.

 

[Keith Seymore]

The 3-speed Saginaws came with 4 sets of ratios. The three I'm familiar with are these:

3.50 low gear used with the 250-six.
2.85 low gear used with 305 and 292.
2.54 low gear used with the 350.

2nd gear, of course, was different for each trans.

The transmissions were all the same other than gear ratios. Obviously the one with a 2.54 low gear could handle more engine torque due to generating less torque multiplication. A 350 engine would easily break a trans with a 3.50 ratio.

Lots of very bad info about these transmission on the Internet, mostly people not realizing there were several ratios used behind various engine sizes. The trans with 3.50 low gear was probably rated at no more than 220 lb/ft torque.

Agree.

One other tidbit that many people do not know is that the Saginaw 4 speed has the exact same exterior dimensions, meaning a 4 speed could be swapped in place of the three speed with no changes to the trans crossmember.

K

 

[MikeB]

Agree.

One other tidbit that many people do not know is that the Saginaw 4 speed has the exact same exterior dimensions, meaning a 4 speed could be swapped in place of the three speed with no changes to the trans crossmember.

K

Same is true for Muncie 4-speeds and TH350.

 

[MikeB]

Hey Keith, a buddy of mine says back in the day he had a late 60s Chevy pickup with 396 and 3-on-the-tree. What kind of trans could have handled that torque? He did buy the truck used, so maybe the engine was changed by a previous owner. He has been a GM mechanic for >30 years, so I know he's not mistaken about what he had.

Edit: Just found a 1969 C10 spec sheet saying the 396 base transmission was a 3-speed manual with 2.54 low gear. It must have been tougher than I thought.

 

[Keith Seymore]

Hey Keith, a buddy of mine says back in the day he had a late 60s Chevy pickup with 396 and 3-on-the-tree. What kind of trans could have handled that torque? He did buy the truck used, so maybe the engine was changed by a previous owner. He has been a GM mechanic for >30 years, so I know he's not mistaken about what he had.

Edit: Just found a 1969 C10 spec sheet saying the 396 base transmission was a 3-speed manual with 2.54 low gear. It must have been tougher than I thought.

One other point: in the truck world "Heavy Duty" is more about durability and less about "high performance"/racing.

That's why you see four bolt main engines and lower compression ratios. I suspect the thinking was that with the primitive (truck) version of a 396 and the column shifted trans that the vehicle was not going to see a lot of power shifting.

K

 

[MikeB]

I suspect the thinking was that with the primitive (truck) version of a 396 and the column shifted trans that the vehicle was not going to see a lot of power shifting.

Good point. The truck 396 probably wasn't anywhere close in performance to its cousin in an SS396 Chevelle, for example. However, the trans still has to handle the big block's torque. And even the 2.54 first gear multiplies engine torque by--wait for it--2.54 times.

Man, that SM465 must have really been stout with its 6.55 first gear!