1972 Chevy truck transmission option?

Hello,I have a question and any responses will be greatly appreciated.
I have a 1972 Chevy C/30 truck with a 4-speed manual transmission.Is it possible to upgrade to a 5 or 6 speed transmission without extensive modifications.I would assume some would be required but I was hoping it can be done without breaking the bank.
Thank you

 

In those years the Muncie 4 speed was pretty common. I thought there was something in New Process that had a five speed - just even swap. That was something we checked into a couple times, but never did anything with it.

I do know of the Browning two and three speed addons, but you have to have room for the gear box behind what you have.

I also remember some of the trailer pullers using an addon which had an electric control. That was more like a reduction speed, I can't remember who made it but it may still be around.

 

Somebody was putting a 6 speed in a 67 Firebird if I remember right, but the trans alone was about $1500 IIRC.

Wondering why you want it? You could go with an overdrive unit as mentioned...seems like Gear Vendors makes units. Yeah, just checked...uhhh got $2900 laying around?

Lots of info on their page about different units though.

 

What are your reasons for the switch?

 

Thanks for the responses.
This is a work truck that I use for projects around the house.When I have to use it on the highway,it becomes obvious that it falls short on gas mileage.I am looking to gather info on how to improve feul effeciency without having to miss a mortgage payment.
Thanks

 

If you have a 454 or a 350 in it, I would look into pulling the Rochester and putting a Holley on it. That would help a lot more than a tranny change.

 

And if I remember correctly a transmission change like what you are talking about would also require a rear end re-gearing. What is your RPM at 60 mph in high gear?

 

I was hoping I could find something at the local salvage yard that was more or less a basic swap that would improve the efficiency when I was driving 60-65 mph.I do a lot of heavy duty hauling with the truck so when Im in the city(Chicago),it works very well.When I have to drive longer distances,thats when a different trans is desriable.I would guess that at 60mph,the engine is humming at about 5500-6000 rpms.Im open to maybe changing the trans first and at some later time the rear gears but as I mentioned,I use the truck for heavy hauling.This is strictly a work truck that I use once a week but I plan on keeping it.
Thanks

 

With a 4.10 you would be turning about 3000-3200 rpms. I would be more inclined to change the carburetor on that truck.

I doubt if you'll find a five speed overdrive in a salvage yard, but there should be a number of Holleys that would do some good for you.

 

Thanks
Marbobj,
I think I will replace the carb.See how the truck responds.It wont happen for a while.Im a UPS driver so my time during the week is a wash but when the wether gets better,I will replace the carb.
Thanks

 

If you are doing heavy work you need the 3/4 ton and by nature you are not going to get good mileage with a heavy truck. If I was going to do anything I would investigate the gear ratio of the rear end it might be geared very low. Yes an overdrive trans would help this but they are not made for heavy work. Good luck RW

 

I also had the same thought.This truck was made to handle bigger loads and so Im sure that is why it has the gear ratios it does but nonetheless I'm going to experiment with some of the suggestions that have been psosted here.I'm in no hurry,so Ill take my time.If they dont improve the overall performance of the truck,Ill change it back to like it was.
Thanks for all the info.

 

6000 RPM's at 60 mph?! Definitely do the carb thing, but check the rear end ratio. It has to be wrong. You're nearly at red line at highway speed.

 

Personally, I don't think a carb change will make THAT much diff. Either need a higher gear in the final ratio of the trans, or a new rearend gear. Your first gear is probably a granny gear, so you won't lose much pulling power if you change the rear.

Don't know about a vehicle this old, but the VIN may reveal something.
Either that or put the rear in the air and find out the actual ratios buy counting the driveshaft and wheel revolutions.

I don't think this truck was really designed for lots of highway running...it's a work truck.

 

In 1977 a company I worked for used the C30 duallies with 454s to haul trailers into Canada from northern Iowa. Those had the Muncie 4 speeds and the 4.10 rear end. Those loaded would get about 9 mpg into the wind and 11 mpg empty, just pulling the hauling trailer. We also had a similar setup with a 3.73 in it, but the mileage was about the same. We put 150,000 a year on those trucks running into Red Deer, Alberta.

We put a Holley on a couple of them and the mileage went up to 13 mpg empty. Loaded with trailers, the mileage was about ten. Loaded, the 454 s were where they were mean to be - pulling.

 

I have a similar problem with a 1977 C20 4X4 454 with 4:10 diffs. Do you know what Holley carb you put in and would the 3:73 diffs help?