Converting a 3 speed manual to 4

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JGC403

JGC403

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Is it straight forward, I don't know much about the early A's. Will the clutch linkage from the 3 speed work for the 4? I think I will also have to convert it from 3 on the tree to floor shift.

What are the ratios in the 3 speed manuals? Will the 4 speed make the little slant feel more peppy?

1964 Valiant /6
 
Pretty straight forward. Change transmission with one from another 65 and earlier with the flange on the output. Use 4 speed shifter and linkage and install a floor hump. The clutch and linkage is the same on both. The way the trans bolts to the bell is different between them so you will need to be sure the bellhousing is drilled with both patterns or get a different bell.
 
So the 3 speed bell can be drilled to accept the 4 speed or were some Bells made to accept either?
 
JGC403 said:
So the 3 speed bell can be drilled to accept the 4 speed or were some Bells made to accept either?
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Some were made to accept either. If you get under the car and look at it it will have other holes drilled and tapped if will accept a 4 speed if you see no other holes other than the ones being used by the three speed you will need another bell.
 
chryslerfat said:
Some were made to accept either. If you get under the car and look at it it will have other holes drilled and tapped if will accept a 4 speed if you see no other holes other than the ones being used by the three speed you will need another bell.
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OK I see. Does having the 4 speed make the slant feel a little more torquey?
 
I am interested in doing the same thing. I have a 73 Dart with a 318. Will the driveshaft be the same length, or will it possibly need to be modified?
Are there any real advantages to that extra gear, or is it just a matter of personal preference? I have an 8 3/4 rear end with 3.23 sue grip. Right now I am running about 2500 RPM at 65 mph when I am on the freeway. It would seem that extra gear would relieve a bit of stress from the motor, but I may be off base.

Thanks in Advance,

Jason
 
1jstrong said:
I am interested in doing the same thing. I have a 73 Dart with a 318. Will the driveshaft be the same length, or will it possibly need to be modified?
Are there any real advantages to that extra gear, or is it just a matter of personal preference? I have an 8 3/4 rear end with 3.23 sue grip. Right now I am running about 2500 RPM at 65 mph when I am on the freeway. It would seem that extra gear would relieve a bit of stress from the motor, but I may be off base.

Thanks in Advance,

Jason
Click to expand...
It wont change the top end RPM. What it does do is split the ratio 4 times to get to 1 to 1 rather than 3 times. If you want to lower your top end get an overdrive 833 and bellhousing. They came in A body length.
 
I just did this conversion on my '72 Duster 225. Look up Brewers Performance. They are a company out of Ohio who only deal with A-833s, and they were recommended to me by the fine folks here at FABO. The entire kit I got cost just over two grand, and it included tranny, bell, clutch fork, Hurst shifter kit, and a gallon of gear oil. Everything bolted right up and I haven't looked back. As far as the gear ratios, if you get the non-overdive A-833, it will be all four gears covering the spread of the original three. First gear will be the same and fourth will be the same as the current third, but having two gears between first and the 1:1 makes a huge difference. If memory serves me correct the three-speed ratios were: 1st 3.09:1, 2nd 1.70:1, and 3rd 1:1. The four-speed for the sixes is: 1st 3.09:1, 2nd 1.92:1, 3rd 1.40:1, and 4th 1:1. If you get an OD A-833, first through third will be the same with a .73:1 fourth gear.
 
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