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3 speed to 4 speed conversion


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You're going to need to find a bell housing for a 4 speed and swap that in along with the transmission. The mounting ears on the 4 speed are different from the 3 speed. You'll probably need to change the floor plate too. I'm not sure about the yoke on the rear of the transmission and driveshaft on a 1/2 ton. Someone here must surely know. I finally got all the parts to convert my 1 ton to a 4 speed, but now I'm thinking about a T-5 to get an overdrive. Mike

Edited by MBFowler
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I have a 4 speed gearbox but it is for a lot heaver truck I think a 2-5 tonner. the drive shaft end going into the engine is to big. The bell housing looks ok, I would just have to drill and tap holes i on different places think.

You're going to need to find a bell housing for a 4 speed and swap that in along with the transmission. The mounting ears on the 4 speed are different from the 3 speed. You'll probably need to change the floor plate too. I'm not sure about the yoke on the rear of the transmission and driveshaft on a 1/2 ton. Someone here must surely know. I finally got all the parts to convert my 1 ton to a 4 speed, but now I'm thinking about a T-5 to get an overdrive. Mike
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I have a 4 speed gearbox but it is for a lot heaver truck I think a 2-5 tonner. the drive shaft end going into the engine is to big. The bell housing looks ok, I would just have to drill and tap holes i on different places think.

Yup, you can do that. The 3 and 4 speed holes are in different locations. My original bellhousing had holes for both.

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I guess one question would be why you want the change. Both transmissions will end up with the same top end gear ratio (1:1), I believe. The floor shifter is cooler in my book so I thought about the same change in my B3C but decided that it was a lot of work and expense for a change that only provided me with a granny gear lower than the one I already had.

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Surely a 4 speed will run morre smoother then a 3 speed on higher speeds. I can already hear the monotone high pitch noice from the 3 speed. :cool:

I guess one question would be why you want the change. Both transmissions will end up with the same top end gear ratio (1:1), I believe. The floor shifter is cooler in my book so I thought about the same change in my B3C but decided that it was a lot of work and expense for a change that only provided me with a granny gear lower than the one I already had.
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If you're looking for a smoother ride at speed you want to bypass the transmission and head on back to the rear axle. Swapping out the rear axle for something with a higher gear ratio will get you down the road faster and smoother. I think there's a thread in here about swapping rear axles from jeep cherokees or from Chevy S-10s. You also get the advantage of modern brakes.

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The optional Dodge 4 speed was for heavy duty use with a super low "granny" low for towing and hauling heavy loads.

For highway and everyday driving you want an overdrive 4 speed or 5 speed. There is nothing that fits directly, you will have to adapt something from a more modern car or truck.

You should be able to have something made up locally. At least, I see some wild adaptations on Aussie vehicles. Maybe some of our Australian readers will have some ideas of where you can get a transmission installed.

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The optional Dodge 4 speed was for heavy duty use with a super low "granny" low for towing and hauling heavy loads.

For highway and everyday driving you want an overdrive 4 speed or 5 speed. There is nothing that fits directly' date=' you will have to adapt something from a more modern car or truck.

You should be able to have something made up locally. At least, I see some wild adaptations on Aussie vehicles. Maybe some of our Australian readers will have some ideas of where you can get a transmission installed.[/quote']

Have you ever done this swap Rusty, always like to hear from those who have done these swaps.

If you have , go any pics , would like to see this, as I have an interest in a T 5 swap for my truck.

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Dontknow it all. I'm just guessing here, but if you say that the 4 spd that you have is from a heavier truck you may also want to check the dimensions of the input shaft, and collar along with the pilot bearing dimensions. If those measurements are larger than those on the 3 speed, you will also have to address the pilot bushing, throwout bearing, and clutch disk. I don't want to go negative on this, but the output shaft may also have a larger yoke on it that won't fit the one on your 1/2 ton's driveshaft, which is more engineering that will need to be done. If the 4 spd that you have isn't the syncro type trans, you're going to have to double clutch it when shifting.

The folks here are right-the 3rd gear in a 3 speed, the 4th gear in a 4 speed, and even the 5th gear in the 5 speed I have in a parts truck are all 1:1 ratio. Mike

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is it safe to say there is no 4 speed gearbox for a 1/2 ton ..:cool:

Nope 100% not safe. The 4spd was optional. Dads 46 1/2 ton junk hauler has the 4spd in it that was in his 40 plymouth. We swapped them.

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If a lower rpm cruising speed and quiet is what your after then

First forget about stock parts and go for the t-5 swap from a chevy s-10 with overdrive, then get rid of your rear axle and get one from a jeep Cherokee or yj like I did and now I can cruise at 60 mph at about 2100 rpm and not have to wear ear plugs and vibrate for an hour after my drive ;)

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Yep, thats true MB..The one I have is bigger and dont fit so I cannot use it..therefore I was looking for an alternative..

Dontknow it all. I'm just guessing here, but if you say that the 4 spd that you have is from a heavier truck you may also want to check the dimensions of the input shaft, and collar along with the pilot bearing dimensions. If those measurements are larger than those on the 3 speed, you will also have to address the pilot bushing, throwout bearing, and clutch disk. I don't want to go negative on this, but the output shaft may also have a larger yoke on it that won't fit the one on your 1/2 ton's driveshaft, which is more engineering that will need to be done. If the 4 spd that you have isn't the syncro type trans, you're going to have to double clutch it when shifting.

The folks here are right-the 3rd gear in a 3 speed, the 4th gear in a 4 speed, and even the 5th gear in the 5 speed I have in a parts truck are all 1:1 ratio. Mike

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You made me laugh! :)

If a lower rpm cruising speed and quiet is what your after then

First forget about stock parts and go for the t-5 swap from a chevy s-10 with overdrive, then get rid of your rear axle and get one from a jeep Cherokee or yj like I did and now I can cruise at 60 mph at about 2100 rpm and not have to wear ear plugs and vibrate for an hour after my drive ;)

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is it safe to say there is no 4 speed gearbox for a 1/2 ton ..:cool:

This has been answered already but I just wanted to add my 2 cents.

My 49 1/2 ton has a 4 speed non-synchromesh transmission. This means that I get to double clutch for every shift, later years with a 4 speed have syncro gears for every gear except low. 1st gear is a grannie gear useful for parades or stump pulling. I did change my rear end for a jeep with 3.73 gear ratio. Top speed is now comfortable at 65mph. The change to a GM T-5 transmission sounds like a better change.

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No, not safe, as I have a '53 half ton sitting here with a 4 speed!'

Yup....and my 52 1/2 ton has a 4 speed too. Remember you could order your truck to be ordered for the intended job.....JOB RATED

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Is it possible to change my 3 speed box , connected to a 218 1/2 ton B2b..into a 4 speed?

if so , where do I purchase the parts?

ok, Reg..so , can I bolt a 1952 - 4 speed to my 1950 218, or do I have to make changes?

I don't know about the length of the drive shaft, the only other thing you would need is the bell housing.

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