dgrinnan Posted April 6 Report Posted April 6 My 47 has the original driveline with a 218 recently rebuilt and bored .40 over. (or is it (.04?), anyway, the motor heads will know. The rear end is 4.11 and recently rebulit with all new axle bearings and seals also. New wheel cylinders and brakes. I found a lot of good information on gear ratios for higway speed. With my current setup I have no trouble cruising at 60 MPH. Is there a transmission that will direct bolt in that will allow me to comfortably cruise at 70 MPH on the interstate? The way it is now I have to stick to the back roads, which is fun most of the time but if I want to attend a show that is some distance away to makes it difficult. Modifications to the bell housing/adapter? Quote
bkahler Posted April 6 Report Posted April 6 (edited) Typically the final output ratio of a transmission is 1:1. Overdrive transmissions have a ratio that is less than 1 where the transmission output shaft is turning faster than the engine crankshaft. Two ways to improve your MPH. One is an Overdrive transmission and the other is changing the differential ratio to less than 4:1 such as 3.73:1 or lower. My 51 has a 3.73 and the few times I've had it on a 55 MPH highway it has been pretty decent. I'm still working out all the bugs so highway driving has been minimal. Brad Edited April 6 by bkahler Quote
dgrinnan Posted April 6 Author Report Posted April 6 I am trying to figure out if there is a straight swap out there from a later model vehicle. Quote
bkahler Posted April 6 Report Posted April 6 Do some research on the Mopar 833 transmission, also known as the NP-440 transmission. I think they came or could be configured with an overdrive. Quote
Plymouthy Adams Posted April 6 Report Posted April 6 19 minutes ago, dgrinnan said: I am trying to figure out if there is a straight swap out there from a later model vehicle. if you did your measurements, cuts and welds during the fabrication phase...yeah will bolt right in.....outside of an R10 unit you going to be making a number of parts or minimum buying them from a supplier. Anything modern braces newer style components that do not lend themself to an easy bolt for bolt swap. Quote
Merle Coggins Posted April 7 Report Posted April 7 (edited) The easier swap is likely a rear diff, or axle upgrade. I was able to acquire a 3.73 diff out of a '50 Plymouth that was pretty much a direct replacement into my axle. I can cruise at 70+ when needed, but sometimes I wish I could drop the ratio slightly to gain a little more drive up steeper grades. A Jeep Cherokee axle seems to be a popular swap. Many have installed 5 speed overdrive transmissions, such as the Borg Warner T-5 out of S-10's and other vehicles. If you search the forums there are several threads on that upgrade. The Mopar 833 OD 4 speed, mentioned earlier, is also an option. Again, search the forums. there are only a couple threads on that one, but they're out there. An OD trans with your 4.10:1 diff would be a good package. Edited April 7 by Merle Coggins Quote
Young Ed Posted April 8 Report Posted April 8 No bolt in options on the transmission side. You could swap for a better diff ratio. Beyond converting to an overdrive transmission there are stand alone overdrive units that some people run. Quote
Solution Young Ed Posted April 8 Solution Report Posted April 8 It would go between the trans and diff and have a separate way to engage it's gearset. Look up gear vendors as they are the most common brand Quote
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