Hi all, I have a bone stock 51 plymouth (except for some 50s bolt on goodies) that i am currently adding an OD stock transmission to in order to improve my freeway driving experience. I beleive this is true because the r10 overdrive is approx 30%. Further, i understand that i can change my rear end pretty significantly and as long as i have the overdrive my freeway driving will be good/great. My stock rearend is a 3.9:1 and my rear tires are 215/70-15s. I have zero experience with changing rear end ratios, thus i thought i would ask those experienced in this matter for thoughts. i really want to show better at the drags so the chevy and hudson inliners cant laugh as they pass me at the end of the 1/4 mile races.......plus i have an 11 year old boy and 9 year old girl that we want to be able to hold their heads high when daddy blows those guys away! QUESTION: Off the line the plymouth is great and the shift to second gear is great, even exciting.....however, when i shift to third its all over as the third gear and rear end ratio(3.9) is too tall(i think thats correct description). The end result is that we have poor finishline performance at the drags because the engine is too low in the rpm band for good acceleration in third gear. Thus, what gear ratios should i be considering for the rear end???????????? I am thinking 4.1:1 because this is available in other plymouth/dodge chryslers of the same vintage and should be a direct bolt in. However, i think there are even higher ratios too like 4.3 or 4.5. How do these ratios drive on the street, with and without overdrive?????? How would they work at the drag strip. Thanks for any wisdom shared, Mike and the 51 Plymouth family racers of Los Angeles.
steeper gears make you accelerate better on the dragstrip, and they make the engine spin faster on the highway. How much you can tolerate depends on you...the only way to find out is to try. You might not see much difference going to a 4.10 it's only a 5% change.
Call George Ache. What you need is what he calls a "fast second". It will wind out much further and makes 3rd much more acceptable. It is a 1 year only gear that fits in our transmission. I have run both the stock and fast second and much more prefer the fast second. Good luck. BloodyKnuckles
easy way to try it is to put lower profile tyres on, just to see if your heading in the right direction, then calculate the % change. and no oil under the nails until you sort out what is required
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