Putting 4 speed manual behind SBC, will it hold up?

[DBK81]

So I have a 1970 service truck that I am likely to buy and part out, it has an inline six and a 4 speed manual, I am thinking about taking out the TH400 from my 1972 and putting in the 4 speed manual. Curious what will be involved short of cutting a hole in the floor and installing a clutch pedal? Also how stout are these transmissions? Will it hold up behind a 375hp 350?

[67 chevelle]

pretty sure those transmissions were rated for like 900 ft pounds , so a smallblock should be no problem

[GASoline71]

Probably an SM420 or SM465 which are pretty stout. But they are granny-low 4 speeds. So if you're looking for any performance... I'd stick with the TH400.

Gary

[davepl]

Remember it's effectively a three-speed transmission with a single-gear low range. The first gear is the "poor man's transfer case" in a way.

I've always started in 2nd when I've driven those!

[DBK81]

Originally Posted by davepl

Remember it's effectively a three-speed transmission with a single-gear low range. The first gear is the "poor man's transfer case" in a way.

I've always started in 2nd when I've driven those!

Yes I remember these from driving an early 80's diesel, I'll stay away from it, thanks for the input, it really is a 3 speed with a super low range first gear.

Thanks guys.

[67 chevelle]

Originally Posted by davepl

Remember it's effectively a three-speed transmission with a single-gear low range. The first gear is the "poor man's transfer case" in a way.

I've always started in 2nd when I've driven those!

True , drove my 59 Apache yesterday , never saw first gear

[weq92f]

Granny gear is good when you're bailing hay all by yourself though!

-klb

[davepl]

Originally Posted by weq92f

Granny gear is good when you're bailing hay all by yourself though!

-klb

You mean you can get out and walk beside the truck while it drives and you load hay?

[Steeveedee]

Originally Posted by davepl

You mean you can get out and walk beside the truck while it drives and you load hay?

Haha, yes, if you have a manual throttle! I've even seen people put their 4wd truck in compound low gear and using a hook with a chain, set the throttle up a little, and get out and help the rest of us push another vehicle out of the snow...nobody in the truck! Good times.

You could walk along side the truck when it was in low/low. I think it had 4.56 gears, too.

[Acorn]

Originally Posted by davepl

You mean you can get out and walk beside the truck while it drives and you load hay?

Yes. But loading is to risky for me. Setting the hay out (square bales) is a different story. Just let it idle in low across the field while you sit in the back and chunk the hay out. And if for some reason a cow is being stupider than normal and gets in front of the truck, you are going so slow the truck will just gently push them out of the way. But trees and fences, well, they don't move so easy!

[weq92f]

Originally Posted by davepl

You mean you can get out and walk beside the truck while it drives and you load hay?

Yes indeed. With a couple folk, you can stack them all the way up too ( one guy in the bed on the stack, the other guy throwing bails up to him). Nobody driving the truck.

-klb

[LongBox]

Originally Posted by weq92f

Granny gear is good when you're bailing hay all by yourself though!

-klb

LOL. My old 250 six with the granny low trans and a 4.11 rear was so low geared that to get it going on ice or hard packed snow, I put it in first, let out the clutch, got out of the truck and pushed against the door. As soon as the truck started to move, I hopped in and went on my way.

[GASoline71]

My 1979 GMC K25 has an SM465 in it behind a 350 SBC. In 4-low and granny 1st, it was like a billy goat.

But for normal driving... I never used low gear. The shifter even showed L-1-2-3-R. So even though it was a "4 speed" it was normally used as a 3-speed.

Gary

[special-K]

Later after these trucks GM started marking the shift knobs with L, 1, 2, and 3 to make them idiot-proof.

[DBK81]

So what would be a good 4, 5, or 6 speed to put behind my zz4 350?

[1972RedNeck]

Tko 600

[special-K]

Good performance 4spds came in cars, such as Muncie M20/M21/M22, Borg Warner Super T10, and Saginaw (if you're not real hard on it). NV3500s are a good 5spds requiring hydraulic clutch as well. I'm not into 6spds. Too much unnecessary rowing for my liking. 4spd is all you need, unless you want O/D, and that's where 5spds come in

[67 chevelle]

NV3500 is rated for 300 foot pounds or less , you will break it , t 10s are common and reasonably priced , I had one of those behind a stout 350 [with dart sportsman heads] for years and it received alot of abuse and held up well , broke alot of other stuff though

[special-K]

Originally Posted by 67 chevelle

NV3500 is rated for 300 foot pounds or less , you will break it , t 10s are common and reasonably priced , I had one of those behind a stout 350 [with dart sportsman heads] for years and it received alot of abuse and held up well , broke alot of other stuff though

I should have said the same thing about the NV3500 I said about the Saginaw 4spd, "...if you're not hard on it". I added that for an easy 5spd option when originally only posting 4spds. I wouldn't say you "will" break either. It's more like you "can" break them... if you're hard on them. I've broke them all. If money is no problem there are Richmond Gear and other new units offered in multiple configurations. I figured cost was a consideration based on going from a freebie granny tranny to now going out to buy and he already has a TH400 that can take the power.

[OregonNed]

Did the same thing in my '66 and always regretted it.

[DBK81]

Originally Posted by OregonNed

Did the same thing in my '66 and always regretted it.

Can you give info as to why your regret going from Auto to Manual?

Just curious.

Thanks for all the input guys I've been keeping my eye open on Kijiji to see if something reasonably close and cost effective shows up.

[OregonNed]

Originally Posted by DBK81

Can you give info as to why your regret going from Auto to Manual?

Just curious.

Thanks for all the input guys I've been keeping my eye open on Kijiji to see if something reasonably close and cost effective shows up.

That truck was a bit of a daily driver, and it was a real pain in the rear in stop and go freeway traffic...

[Don Brace]

My 71 Longhorn has a Saginaw three speed overdrive with column shift. Good performance and mileage. I installed this when I built the truck about five years ago. It's not a hot rod but fun to drive. Daily driver during the summer.