I was over at Randy's Ring & Pinion today, inquiring about what kind of goodies they had for the 8 1/4 rear I've got in my Dart. The guy that was helping me gave me a bunch of suggestions (and a price list of what they could do ), one of which was taking the driveshaft in to be lightened.

I've noticed some of the V8 crowd having this done, but haven't heard the results or benefits of doing this. I assume that with less rotational mass (weight), the driveshaft will be able to accelerate and spin faster, translating to better acceleration off the line? Would it be worth it to have this done on a Slant Six car?

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Erik T.
1974 Dodge Dart Swinger - 225, A904, 8 1/4, B5 Blue w/ White Vinyl
1982 Chrysler Cordoba - 318 Lean Burn, A999, 7 1/4, VC4 Glacier Blue w/ Dark Blue Vinyl

someone on here will know the numbers, but i'm guessing 5hp'ish gain? i know the aluminum ones spin nicely and are about $500. how much $ is it? what do they do, drill holes and make it look like swiss cheese?

Talking to the shop I was referred to, it sounds like they put it on a lathe and shave a bit off the diameter of the driveshaft. They rebalance it and install new u-joints. They said they can usually drop around 2-6 pounds off of stock V8 driveshafts.

Forgot to ask about price, but it probably would be cheaper than buying lightened driveshafts from Mancini for around $300-400 depending on whether you buy steel or aluminum.

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Erik T.
1974 Dodge Dart Swinger - 225, A904, 8 1/4, B5 Blue w/ White Vinyl
1982 Chrysler Cordoba - 318 Lean Burn, A999, 7 1/4, VC4 Glacier Blue w/ Dark Blue Vinyl

Not a good place to try and save a few pounds by machining. Buying an aluminum or carbon fiber driveshaft would be okay, but don't try to weaken a stock steel one to save a few pounds!

I think I'l side with TimK on this one. Engineer in a weak point that YOU want to break, if something has to break. Build a strong rear, trans, and driveshaft, and leave the u-joints as the weak link. They're cheap, and relatively easy to fix.

Roger

It would also be a good idea to put a driveshaft safety loop on your car if you think you might break a U joint. You can order them out of Jeg's or Summit.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

The gains from a light driveshaft are minimal on ET. Aluminum shafts go in and out of favor with the guys who race Stock, but the gains are generally not worth the expense unless you need every last .001 of a second.

One of the Mopar rags did a back-to-back test in a '67 big block R/T. An aluminum shaft was worth about .03 in the quarter over the stock shaft that had the big iron balance ring on it.

Turning down the stock tube seems kinda dangerous to me, unless you like driveshafts coming through the floor.

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Official Cookie and Mater Tormentor.