1965 Plymouth Fury II, 318 Poly/Auto, Rear end Gear Question...

7938 Views 5 Replies 4 Participants Last post by militos, Feb 5, 2013

militos

Discussion Starter · Feb 3, 2013

Hello every one I'm new here, I do own this car and it runs real nice with the drive power train that orignally have on it, My only issue is the RPMs at HWY speeds, I have a automatic 3 speed tranny and I wonder if there is a specific rear gear that I can Install, or if there is a newer OD auto transmission that will fit right into the belhousing of the Old 318 Poly engine??

Can I tell the gear ratio from my differencial by decoding the VIN number??

Thanks.
militos.

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Bearhawke

· #2 · Feb 3, 2013

Quick and dirty: I'm guessing you Fury has ca. 3:23 gears. One 'easy' way to drop the highway RPM's is to go with a taller tire and wheel since 15 inchers were an option on your Fury, you probably have 14" wheels and tires. Note you may have to have the speedometer recalibrated since it will read fewer MPH at a specific speed.

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valiant67

· #3 · Feb 3, 2013

The VIN won't indicate the rear axle ratio, but the data plate under the hood might. I think the 3.32 is a good guess but there were many options for ratios back then. There is no easy bolt in OD auto transmission, though it can be done. Likewise you could swap gears but a gear to reduce highway RPMs will make the car slower from a standing start.

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covertopps

· #4 · Feb 3, 2013

Surprising that you are having high RPM's on the Fury. I had a 1965 Fury III convertible and that had 2.76 in the back and it cruised at 80. Check the rear end to see what the gear ratio is. There might be a tag on the rear end attached to one of the bolts on the chunk. If not you can do a check by lifting the back end of the car off the ground. Put a vertical mark on the bottom of the tire and one on the yoke and pumpkin. Rotate the tire (in neutral after the car is secured) until the mark on the pinion/pumpkin line back up again. Look to see where the mark on the tire is and that should tell you your ratio (pretty close) I know my explanation is a bad one, and someone will be able to correct it or add to it. It is one of those things that I can do but explaining it is different. The 2.76 gear is the highway one that went into a lot of big Chryslers and they are pretty easy to find. If you have a sure grip then no doubt you have a lower gear ratio. You VIN will not tell you the gear ratio, but your fender tag might....Maybe. The line sheet from the car would tell you the code for your rear end if the car has one. They are typically under one of the front seats, or possibly the back seat, sometimes on top of the glove box liner.

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valiant67

· #5 · Feb 3, 2013

The sales brochure mentions that the standard ratio with a V8 and auto trans is 2.94.
It's possible an optional ratio was selected with yoru car or that it may have been changed becasue 2.94 shouldn't be that bad on the highway even with 14" tires.

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militos

Discussion Starter · #6 · Feb 5, 2013

Great, I will check the rear end for that Tag first and will check the tag on the fender or door, but I'm very sure that I have the big gear.

Thanks every one.

And one more question,,Where can I put an Add for my car For Sale in this forums?
this car just uses to much space to park and I really want to let it go to one of the Plymouth Fans that really apreciate this cars.

Thanks.

militos.

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