The Stovebolt Site Forums The Shop Area Driveline 1949 chevy 3/4 ton rearend swap

I've posted this before but need to know again, what is the best solution to keeping my 1949 Chevrolet 3/4 ton truck stock, but being able to run 60 mph without harming the engine.It has the original rebuilt 216 in it. I've been told a 410 out of a 68-72 Chevy 3/4 ton truck, but that I'll only gain 5 mph, if this is true, is it worth the swap? Also been told to swap the complete rearend from a 1987-93 Ford E-250 Van, has anyone done this swap? What would be the best swap that would look and fit near original with the 8 lug wheels and gain me 15 mph? Thank You!

if you use a Ford rear end you for sure wont keep the truck stock
or any other changes... you will have to decide what is worth any swap.. I would not change anything for a 5 mph increase..

keep it the way it is and enjoy the scenery

Sig, I've had this swap installed now for a couple years and it's great in all the gears. I drive my truck up the freeway 60 mph no sweat. Best thing I've done for this truck.

SIG- I've purchased a 14 bolt rearend from a later model Chevy for my 3600. The Ford rearend may be a little too wide for your truck if you're planning on keeping the origianl truck bed. You need to find a rearend that's 63-65" wms-wms (wheel mounting surface). Most late model rearends are 65" and wider.

GM made a 63" wms for dually trucks, that is pretty much the perfect width for your truck. I'm actually using a rearend out of a SRW (single rear wheel) truck which is 67" and using dually hubs to narrow it up to 63". The problem being is that now I have to get creative with the brakes. I'm doing a disc conversion, so it's no big deal.

If you can't find a dually rearend, you can always use a 67" 14 bolt rearend and use your hubs off the Eaton. It'll give you about a 65" rearend. Then all you would have to do is weld a new flange on the rearend so you can reuse your original backing plates and drums.

http://s1074.photobucket.com/user/w...amp;_suid=136629145223703088780721707863

http://www.pirate4x4.com/tech/billavista/14b_bible/

Do you have an open or closed drive shaft? If it is closed and you want to keep the rest stock get Patricks 3:55 kit. That will cure your problem. My 46 Burb has a 3:53 which is perfect. I had a modern rear end narrowed with larger brakes for both my Suburban and my 41 1 Ton pick up.

If you change rear ends you will have to deal with width, brakes and hand brake cables that will be different.

MURYDAVE- The 3:55 won't work with the 8 lug, full float rears.

Thanks for clearing that up. I thought they had the same 6 bolt lug rear end as the 1/2 tons.

I did it. Please PM me.

Has anyone actually done this swap yet? I'm trying to get some validity to the information. I keep seeing "someone told me" !! Trying to get someone that has actually done this to say yes it works or no it doesn't

had a 49 3/4 ton and swapped my 5.17 pumpkin for a 410 out of a 1970 chevy 3/4 ton truck and it works and it took me an afternoon to do with some guidance from a friend. Now I gained about 10-12 mph and decreased my RPMs but if you have the 4.57 rear end in your truck it is my opinion that it is not worth the time or effort to gain 5-6 mph. Based on reratio charts you need to get a rear end in the 3.38 range to cruise in your truck. This is my opinion based on experience.

YES, I have done it, Into my 1951 Chevy 1 ton truck with 1958 Chevy 235 engine, SM420 transmission, from a 1970 Chevy 3/4, V8 engine and Automatic Transmission rear gear with 4.11 ratio. IT WORKS as advertised! You pull the axles out about 3 inches each side,Unbolt and Remove old 5.14gear set onto floor jack and Raise new 4.11 up and bolt into place. Add gear grease, Have a Beer or 3 and go for a cruise in the Left Hand lane. I have driven 70 MPH measured on GPS and still had some pedal left unused. BUT Is your Steering Up To It? Brakes? Can you live with Speedometer being inaccurate or are you willing to buy the adapter? Do you have 3 point seat belts? All of these questions become Much More important when you run an A D truck at these speeds. I must admit, I do have some work to do ! Now Get out there and beat the bushes, These Eaton HO 72 gear sets are available BUT you wont find them driving the Interstates! I do have pictures on this computer somewhere of a 4.11 Eaton gear set and the P/N on the side of the ring gear
Keep us in the loop . Jerry

I'm working on the same problem in my '53 3/4 ton. Can you get a chev rear end in the 3.38 range that will work with 8-lug free floating axles? If so, what does it come out of? If not, then what is the best you can do to a stock gear ratio that will work with 8-lug?

Im working on swapping a 76 blazer 12 bolt from a 4x4 in to my 51 3/4 ton. About to go measure it up right now.

Wrench fetcher, what was it that you had done? Or what did you find that worked?

Dave

You have a different animal than what I have, I have a HO52, I believe the 72 was what was standard in the one ton.

I have a 1949 GMC 3/4 ton with 456 with open drive shaft. I would like to change third member to higher gears. I saw in your 7/2/13 post that you have done this but I haven't been able to pm you. No one seems to give a straight answer on what you can do. Thank you.

This is almost thrilling to hear about. I have a 1953 3600 with the granny 4 on the floor. torque tube etc. If changing out the gears in the pumpkin gets ya an additional 5 MPH what your RPMs? Mine is smooth on the hiway up to about 60 mph but I'm turning at 3100 to 3200 rpms. It works but I'm worried I'm pushing the 1959 235 motor too hard. Any comments? Advice?

If you have a torque tube it’s not a 3/4 ton.

If it is a 3/4 ton this tech tip will help.
https://www.stovebolt.com/techtips/axles/1%20Ton%20Upgrade/

Thanks Grigg,

Admittedly if I were called a shade tree mechanic it would be a huge compliment. I bought the vehicle October of 2016 and my wife calls it my mistress. Turns out via the motor markings it has a 1959 235 in it complete with a 1956 top end but I'm learning its common for crate engines of the era to be mismatched top and bottom. I *think* I'm looking at torque tube ..and feel fairly confidant I'm have the Eaton HO52* axle assembly (4.57:1 ratio) as it is HUGE compared to a friends 3100. I can see why folks call it a pumpkin. In the end it seems mods were done in the distant past and I'm struggling to figure things out. To date it runs very well ( and I'm somewhat proud considering my skill level) Everything is smooth ( after a lot of fumbling and tinkering on my part) but I'd like to roll down the hiway at 55 to 60 and not be straining the engine at 3000 rpms. Don't need a hot rod...just need to keep it in one piece!

The 3/4 ton may have a partly enclosed driveshaft, just a short piece behind transmission.
A torque tube is rigidly attached to the differential, in it is the driveshaft, 1/2 Tons have those.

For your 8 lug axle you will enjoy 4.10 gears as explained in the tech tip.