3.5" aluminum driveshaft 54" in length, who runs one?
 

This topic is under discussion on my Super 10 build thread but I want more to see the question so posted here.

I am curious if some of you have an aluminum driveshaft, 3.5" OD, .125 wall, 54" in length, in race service.

The Super 10 will have a 32 x 14 bias tire, 6.0 gear, and for purposes of math use 5% converter slip. Since it has never run the finish line RPM is unknown.

The expect ET is 10.40 - 10.30 range.

One poster explains that finish RPM will exceed the safe limits for a 3.5" shaft 54" in length.

Another poster ask, "in the olden days how did the old modified and comp cars turn 9,000 + RPM with most using some from of factory driveshaft?"

Just for conversation I suspect the on-line critical speed charts we find have a large window of cushion.

I look forward to comments.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

PS, I have the above explained driveshaft in house. I do plan to test 1/8 mile with that shaft.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

I was told by a driveshaft mfg that my small block (327) Powerglide equipped 1971 Nova needed a 4' aluminum driveshaft if I were going to run it to 7500 rpm. My thoughts were that this was not needed. I have been running a 3' MS shaft with 1350 u joints (If my memory is correct it is 55' long) and have not had any issues. It is what I have used in numerous cars over the years without issue.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

Mark Williams has a chart/formula that they use for driveshaft recommendations. It may be even on their web site.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

Though it's not quite 54inches long (52) I've run a 3.5 inch Mark williams aluminum shaft since 08 6.20 gear 138 MPH 9900 RPM you can do that math, then look at their chart. I BELIEVE they leave alot of room for safety. Just my opinion.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

Joe, I agree about the safety factor. I think you can find many situations like you describe with your combo.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

Larry,
My car will not clear a 4" shaft. I run a steel Shaft 63" long 3.5 diameter. I have turned it 10,200 through the traps pretty often. Most runs were near 9600 to slow down a little & save index. I was told it wouldn't do it, but I have over 200 runs on it. No signs of stress. I know I put more gear and similar power on it than your combo...Go for it...
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Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

Adger, I plan to run the Thunder Road date in September. Look me up.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

If I remember correctly mine is 52". I absolutely love Mark Williams products and have many of their rear end components. When I called about a driveshaft a few years ago they told me I needed carbon fiber. WHAT! This is a mid 11 second bracket car. I think the charts are VERY conservative as far as critical speed ratings. I don't have room for a 4" shaft. I ended buying from a friend with a similar car a Strange 3" chrome moly shaft. No vibrations. A friend with an identical car to mine is using a 3 1/2" aluminum shaft as well and this car is at 10 flat. We both run Jerico's.

Re: 3.5" aluminum driveshaft 54" in length, who runs one?
 

My driveshaft is 57" , one of the longest driveshafts MW HSS ever made..they made a 3.5im diameter first and it last maybe 3 runs and it broke close to the end....so we sent it back and they requested a 4in instead....its been in the car 14yrs later and still no issues