Driveshaft Specialist Inc - Warning

[GT_Rich]

Just a heads up to anyone shopping for an aluminum driveshaft. Driveshaft Specialist Inc (http://www.driveshaftspecialist.com/default.html) will be a top Google search result if you're shopping around for driveshafts. Nice enough folks, good turn around time. Unfortunately, they do not understand critical speed calculations on the shafts they sell. They will quote a critical speed based on the tube length only and not the welded shaft assembly. There's usually about a 10% reduction in critical speed for a finished driveshaft with u joints and a slip joint.

I have a long wheel base car and I run 4.10 rear gears. so I needed a 56" long driveshaft that could turn at least 7,000 rpm. They quoted a shaft speed of 7100 for what they would build me (3.5" alum). Well, it hits critical speed at 6300 rpm and creates a sharp and sudden vibration. Enough to crack the tail housing on my trans.

I brought this to their attention and the best offer they could make me was to buy back the shaft they made for $175 and I would have to pay $50 in shipping to get it to them.

I'll have someone else build the 4" aluminum shaft that should have been recommended to me in the first place.

[John McIntire]

$175 for a driveshaft?

That should have been your first sign...

[GT_Rich]

I paid $500. $175 was what they offered to give me back.

[John McIntire]

Ohhh. I've had great luck with Denny's Driveshaft. It's been a few years since I've needed a driveshaft, but I used then for both my Chevelle and Camaro. They had a policy where if you could bend or break it they'd replace it for free.

[409novaman]

https://www.dynotechengineering.com/
I have one and am very satisfied with the service and quality.
They are local to me, I went in and talked to them and the part I bought was like a jewel.

[anguilla1980]

I also went with DynoTech for my new driveshaft.

[GT_Rich]

I contacted Dynotech after cracking my tail housing. They suggested a carbon driveshaft to the tune of $1544. Carbon was to keep the diameter small so I wouldn't have to further modify my tunnel. I can't justify a spend like that for the one or two times a year I am on a road course.

After lots of research and some dumb luck, I realized a 2005 to 2012 Nissan Pathfinder RWD version has a 56" long aluminum driveshaft that is 5" diameter and uses 1330 u joints. Critical speed with this shaft and my gear ratio will be about 160 mph, and I'll never be there.

I picked one up from a junk yard for $100 and swapped over an extra yoke and flange that I had laying around. I now need to modify the tunnel, but the savings is worth my time.