4spd v 4spd O/D

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70DusterDev

70DusterDev

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Which is better/stronger? Is it worth paying the extra for the O/D? I keep reading about people stripping their O/D trany's and putting regular 4spd gearing in them. Lets hear your opinions
 
The OD versions almost always sell for peanuts compared to straight 4spds. You will regularly see them selling for $100 or less.

They are seen as not as strong because the vast majority had an aluminum case that could wear where the counter shaft runs in the case. If the case becomes oblong the gears can separate and ultimately break. This would be the same situation if you were to put regular gears in the aluminum case. It can be fixed by machining out the hole in the case oversize and pressing in a steel bushing. This is really only an issue if you are really stressing the tranny like regular power shifting with a big block.

The OD tranny came out as an attempt to increase gas mileage. The cars they came in had relatively low numerical rear ends so the first gear ratio was a high numerical ratio to provide acceptable acceleration from a stop. This results in a very wide ratio spacing between gears that is not ideal for performance.

All that being said I have one in my 68 Barracuda behind a 360 with approximately 370 HP and have 3.55 gears in the rear end. My car is a street car and I have no issues with the gear spread, the 360 has plenty of torque to easily pull through the gear spread. The car has run 13.7 sec at 102 mph in the quarter with a very traction limited 2.2 second 60' time so the gear spread isn't killing performance. I pulled the tranny from a D100 pick-up with well over 100,000 miles on it and have added another 63,000 miles in the cuda. The only thing I have done to it is change the oil and before I first intalled it i replaced all the seals and gaskets.

What I do love about the OD is I run down the high way at 65 mph at just a tic over 2000 rpm and get 21-22 mpg.
 
I Have A OD Behind My 550HP 440 And Works Like A Charm, No Track Time But Heavy Foot On The Street, 70 MPH On The HWY And Runs Around 2200 RPM. With 391 In The Rear. Best Of Both Worlds, I Love Mine.
 
Interesting, because i can get a 4speed O/D with the bell house and all linkage and pedals and driveshaft for 450-500 but then i have to buy a flywheel and clutch and not sure if shifter is included and its actually missing on part of the linkage. Then i have to buy the new hump and make the support on the frame for the linkage. OR i can get a regular 4spd, bell house, flywheel, driveshaft, linkage, shifter, pedals, support bracket (to weld in), and hump for around 1500 from another guy... not sure which to do?
 
How much highway driving are you planning on doing? A torquey motor will handle the gear spread on the OD fine, but if you have a bigger cam it will not work as well. The OD will work better with at least a 3.23 rear, preferrably 3.55 or bigger. If you plan on going to the track much, you would be happier with the regular four speed.
 
Mostly street, i have 391 gears and a 470/470 270/270 cam. Its plenty torquey so it should be alright? I dont know what I will be doing for highway but most definitely more highway use than the strip.
 
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