The Stovebolt Site Forums The Parking Lot Big Bolts auxilary transmissions 2speed axles etc

Has anyone installed an auxilary transmission in a TF truck? And where would one find a 2 speed rear axle for 56 57 6400 electric shift? Will the dropout 3rd member fit in the existing axle housing?
Another question, what kind of rear end ratio are folks using on these bigger trucks to get some decent hiway speeds and fuel economy? Anyone here swap in a big block?

Hey truckolet. I'm actually in the middle of a big block swap along with a clark OD tranny at the moment. should be complete in a month or two. I'm using the stock gear ratio for now. But with the OD it will do highway speeds no problem. Hard to seriously talk about fuel economy in a large truck with a big block. But i imagine it will be very similar to what I was getting with my old six.

Sounds good, what are the ratios and tire diameter?
I bet it will pull much better than the 6

More horses take more gas if you use them. Back in the 60's, I pulled a gasoline tanker and a grain trailer with a GMC with a 371 cu. in. Olds that would run 75 mph. I averaged 2 miles to the gallon. Field trucks that brought grain from the farm to the elevator with something like a 270 GMC, 261 Chev or 292 Ford averaged about 5 miles per gallon.

Truckrolet,

Your 6400 2-speed is most likely the 15,000# Corporate GM rear with vacuum shift. Chevrolet never made an electric shift to my knowledge (the optional electric shift rears were made by Eaton). So third members are not interchangable. The GM rear will have a ratio of 6.40/8.72 and the optional model 16600 Eaton rear has a ratio of 6.50/9.04.

Need to know what tire you have to know the diameter. I think the 10.00 x 22.5 (same as the 9.00 x 20) is about 38" tall.

My 57 Fire Truck with 11.00 x 22.5 tires and a 6.14/8.36 Eaton runs 65 mph all day long and it gets 7 mpg. It has a 200 hp V8 with a direct drive 5-speed trans and weighs 14,200# without water in the tank.

Mike B

Wow I didn't expect to hear such poor mileage. I've been thinking about driving my big bolt cross country but not with mileage like that.
I have the vacuum 2 speed rearend. I was wondering if there are any known problems to look for ? I think the vacuum is leaking somewhere along the line. The two speed was working but isn't now. I haven't looked into it at all yet. Thanks for any info .

I don't have a big bolt yet, but looking at one. Only a single speed rear end. If I wanted to haul or pull a load, I would change the 6 for a big block so it would move at a reasonable speed on the freeway. And with fuel mileage like posted here maybe a duramax diesel would be a better idea.
At 7 mpg that is still better than a big class 8 truck and cheaper since gas is still less than diesel is.
I bet with proper gears and engine tune better mileage could be done.

I think my 7.8 mpg is as good as it gets for my truck. I just had the heads rebuilt and replaced the rings. I've driven my truck from Maryland (near Washington DC) to the middle of Kansas and I believe the gears are as tall as possible based on the available power. If you had a larger HP V8 you would have to calculate the gas consumption based on the same rpm I'm turning now. So the question is, what kind of milage would a BBC get turning 3500 rpm all day long?

I remember hearing a BBC in a Suburban only got 10-12 mpg whether they were pulling or running empty, so I don't think a big truck would do better then that.

Your mileage may vary...

Mike B

big blocks suck gas for sure, and if you want it for the highway, an OD is the only way to go, I figure I'll be lucky if the 454 in my bus will get 8-10 taking it easy with a 4L80 trans [easy fit for a 454]

and the 2 speed axle won't help much, you have a 7.20 with the single speed, and the 2 speed is 6.40 at best, 8.72 otherwise

Bill

I'd like to go for around 2200 or so for 60 or 65 mph. I think that is what my F250 460 does. Yeah will be getting rid of the F when I get the right setup.

My '53 GMC w/302, Brownie, 6.6 rear, flatbed, got 10 to 13 MPG w/ light loads, 60 to 65 MPH, on a trip. Stock carb., head milled .060"

Ed, what size tire and what is the final ratio on your brownie?
My '52 COE with the 302, 8.25-20 tires, 6.5 rear and 0.86 OD Clark really won't get better than 5-6 mpg. And 55 sounds plenty fast to me. Although I've wanted to put a tach on it to see exactly how fast it's turning, I'm probably leaving some on the table. The 302 starts and runs better than almost any carbureted vehicle I've ever driven.

Scotts, a heavy vehicle with no aerodynamics and a carbureted engine, I think you are right on the money with your mileage. Thats what bob tails did 60 years ago, and I don't see that they can do double that 60 years later. It will run a lot faster than 55, but you will get a lot of wind noise, fan noise and valve noise, but it won't hurt it any. But it will use more gas to break more wind.

900x20 radial tires, 5831 Brownie, didn't know OD ratio,

Where is a good place to find auxilary transmissions? Or even the 5 speeds?

http://www.vanderhaags.com/nojs_body.php

http://www.geigertruck.com/

http://berryhillauctioneers.com/upcomingauctions.php

The auction in Dallas is going to have a lot of old stuff.

One must look for oneself, if one asks, yards won't know, so just figure out a way to look for yourself, take your pocketknife to scrape the dirt off the data plate, a rag, old clothes,(make sure wife if gone when you return to change out clothes) might like to know that most trans. have an O in the data plate to indicate OD ratio, most have OD against the panel, far right shift rail. Some Brownies are Direct and under, only, so check carefully.

Make sure get all shift linkages and driveshafts, shifters; they will throw them out anyway, very difficult($) to find replacements.

I have a 1954 1.5 ton 4400 running a 235, sm420 and a brownie 5831. I believe the OD is 28%, there are several 5831 ratios. Found the brownie in a pile of transmissions they didn't even know what it was. Ed Pruss is right the linkage is very difficult to find. My truck runs great at 63-65 mph with good stock brakes and a tight front end (35k original miles). For a big truck old truck it drives great at highway speeds. It does lack power on hills in OD but I have a 261 I plan to install.

2200 R.P.M.'s,Or that's what you're willing to spend,to achieve your goal? Are you farming the work out,or doing the mod's yourself? I have a friend,who's grafting a 2-ton Studebaker cab/chassis/frame. He's building another 4X4.(Origional was done 25-years ago,and went through a 327,2,350's,and a 305.Currently on its 5th engine,but still ORIGIONAl SM 420!!("Runnin'with the Big-Bolts",C/O "Photobucket). We both help each other out,on all the work. saves a lot of money on labor,and safety-wise,it's best to have a "hand"."Two heads are better than one" "Did you tighten that bolt?" Hand me that wrench"... I tend to work longer,and enjoy it more,if I have a helping hand,with a sense of humor. He's like a brother,and I bought the '55 from his brother. Ron wouldn't even let me paint my truck! He gets into it,and half the time,I'm the "Hand"!! I may be wrong,but I wouldn't think it would cost that much,for parts.

2200 R.P.M.'s,Or that's what you're willing to spend,to achieve your goal? Are you farming the work out,or doing the mod's yourself? I have a friend,who's grafting a 2-ton Studebaker cab/chassis/frame. He's building another 4X4.(Origional was done 25-years ago,and went through a 327,2,350's,and a 305.Currently on its 5th engine,but still ORIGIONAl SM 420!!("Runnin'with the Big-Bolts",C/O "Photobucket). We both help each other out,on all the work. saves a lot of money on labor,and safety-wise,it's best to have a "hand"."Two heads are better than one" "Did you tighten that bolt?" Hand me that wrench"... I tend to work longer,and enjoy it more,if I have a helping hand,with a sense of humor. He's like a brother,and I bought the '55 from his brother. Ron wouldn't even let me paint my truck! He gets into it,and half the time,I'm the "Hand"!! I may be wrong,but I wouldn't think it would cost that much,for parts,as long as you already have an engine.

With regard to the big blocks, they use a lot of gas. I've owned a lot of 60's camaros, and muscle-flexing big blocks would get between 5 and 9 mph in a very light car. Living in the country and having to drive, I went to a stroked small block, yielding a 388 ci... (350 with a 400 crank). The car, with that engine, could get me 17mph if I was nice, but would scream when needed, pretty close to the performance of the BB's. I love BB's, but I will never go back. I stongly recommend stroker motors for those who wish to go fast, or pull a load, but want fuel economy also. Just my 2cents.

My '54 GMC 350 has a 302,Clark 5 speed w/0.85 overdrive,5531 Brownie w/0.74 overdrive and a 1350 vacuum shift 2 speed w/6.40 top side. Until I have good tires on it I won't know for sure what to expect for mileage. I DO know it runs out smoothest and quietest with the trans. in direct and the Brownie in over,and my number-cruncher says that should show me 75 mph at about 2600 rpm. Redline,in double over would be about 105 mph,if it had the power to carry it,but I don't see that ever happening,intentionally. I'm thinking about converting a throttle body fuel injection set up,but have a LOT of studying to do on that.
Speed