3 Speed to 4 Speed?

[Martin64]

I was considering swapping a TH350 into my truck in lieu of the current 3 speed on the column, but I'm thinking a 4 speed (granny low) would be a better application. Has anyone done this and what else, besides cutting a hole in the floor and a possible change in driveshaft length, is involved? And what's a good 4 speed to put in?

[66GMC-Canuck]

I have a SM465 in my 66 and that granny low is low. You could pull a house with it. You have a granny low and 3 gears you might find the 3rd on yours to be the same ratio as the SM465. So all you will gain is ultra low gear or is that what you want?

A good 4 speed with no ultra low is a Munci M22.

[Eagar1]

If its a daily driver, go the m22 route, probably cost you in excess of $1200.00. I would probably go to a 700R4, brand new about $700.00 would be a better easier and cheaper upgrade.
If you want a TRUCK, go the granny route, and if you need it to go on the highway, get taller (lower numerically) rear end gears. You can get a good 4-speed for around $200.00 or less, and that may include the flywheel and other misc parts you need to convert and then swap out your rear end gears for about $300.00 if you really needed to.

[markeb01]

As stated above, it really depends on how you want to use the truck. The granny box is really a 3 speed with a compound low gear. It's an extremely large and heavy transmission, and slow to shift because everything in it is big and heavy duty. If you're going to haul logs out of the woods, or pull stumps, or horses or something it would probably be great. It is longer than the 3 speed and will require shortening the driveshaft. If your 64 still has the original bellhousing engine/trans mount it's a simple bolt in.

If you want a hot rod, either the Muncie M21 or M22 are good candidates, or the Borg Warner Super T10 is also an excellent choice. The M22 only comes with a 2.20 low gear, and is the coolest sounding transmission ever. The low gears are cut straighter than normal and are very distinctively loud. The M21 has various ratios available, as does the SuperT10. Either of these will also bolt right up to your bellhousing, and the driveshaft shouldn't require and length change, although it may need a yoke change depending on how new the transmission is. The later transmissions use the larger Turbo 400 yoke.

For general purpose driving, you really can't beat the Turbo 350. It is also the same length as the 3 speed stick and 4 speed stick, although you will need a rear mount crossmember under the tailshaft. I had one in my 1960 for 10 years and it worked perfectly with a mild shift kit installed. You will also need a trans cooler of some type and the kickdown linkage to the carburetor. If you want a semi-original look, you can install a Genie Shifter or Lokar shifter and they can be adjusted to come up through the original 4 speed hole in the floor pan.

Mine was working perfectly when I got the bug to run with 3 pedals again. For a daily driver the T350 is an excellent transmission. It's smaller and lighter than a Turbo 400 and shorter than the newer overdrive transmissions.

[markeb01]

One more thought, if what you're after is a really low 1st gear without the bulk and weight of the granny trans, you can always go for a Super T10 with a low 1st gear ratio. They are available as deep as 2.64, 2.88 and 3.44. I have the 2.64 with a 4.10 rear axle and it launches like a rocket, but doesn't run out a 3 mph like the granny trans does.

[Martin64]

Yes, I want a lower gear. I'm sure this truck is going to eventually pull a trailer or 2 as well as haul a few motorcycles. I'm more comfortable with 4 speeds and pulling trailers than I am doing it with automatic transmissions. I don't really care about the speed in which it shifts. I know you don't always use that "under" gear, but it's sure nice to have when you need it or just need to move at an idle. With this 3 speed that's in it now, it's hard to get up on a set of ramps without burning the clutch....and the 4 speeds are alot quieter

[Martin64]

I think the rear end gear is about right. I'm running a little lower profile tire than stock and the comfortable "cruise altitude" is about 62 mph. The "legal" speed limit in California with a trailer is only 55 mph, so with a trailer it should move along comfortably without having to drop a gear too often going up hills at freeway speeds.

[markeb01]

I wouldn't enjoy putting it in (because of the size and weight), but it sure seems like the granny box would be ideal for your application. The best part about those transmissions is they convert a "truck" into a "TRUCK". The darn things make you feel invincible. You can lug a house along at 3 mph all day, and size of the engine really doesn't matter all that much. They tolerate enormous punishment from indifferent drivers and virtually never break. I would imagine if you can find one, it probably won't be all that expensive since they just aren't very popular. I actually took mine to the dumps since nobody at the time wanted it.

[Martin64]

I'm sure it'll do fine behind the 230 until I get a 350 together. I'm really in no hurry for the engine change because the 230 is doing fine, but I'd like to get the 4 speed going as soon as I find one.

Thanks guys!

[Tx Firefighter]

You're going to need to convert to a high hump too.

[Martin64]

Originally Posted by Tx Firefighter

You're going to need to convert to a high hump too.

Road signs are cheap and very un-noticeable under the rubber mat.....thanks for that heads-up. I knew there had to be more to be considered and a taller transmission never crossed my mind.