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    Results 1 to 7 of 7
    1. #1
      Join Date
      Jan 2014
      Posts
      35
      Country Flag: United States

      Driveshaft Specialist Inc - Warning

      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.

      Rich
      1962 Mercury Comet, 32V Cobra engine, 5-speed, 8.8 rear, custom suspension
      1965 Ford Mustang, supercharged 5.0 EFI


    2. #2
      Join Date
      Aug 2004
      Location
      NJ
      Posts
      1,231
      Country Flag: United States
      $175 for a driveshaft?

      That should have been your first sign...

    3. #3
      Join Date
      Jan 2014
      Posts
      35
      Country Flag: United States
      I paid $500. $175 was what they offered to give me back.
      Rich
      1962 Mercury Comet, 32V Cobra engine, 5-speed, 8.8 rear, custom suspension
      1965 Ford Mustang, supercharged 5.0 EFI

    4. #4
      Join Date
      Aug 2004
      Location
      NJ
      Posts
      1,231
      Country Flag: United States
      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.

    5. #5
      Join Date
      Feb 2008
      Location
      Macomb County, Michigan
      Posts
      34
      Country Flag: United States
      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.
      This is getting very expensive?

    6. #6
      Join Date
      Sep 2016
      Location
      Bakersfield, CA
      Posts
      540
      Country Flag: United States
      I also went with DynoTech for my new driveshaft.
      http://www.TheFOAT.com/92GTA
      1969 Pontiac Firebird
      w/Butler 535ci IAII aluminum block & Edelbrock 340cfm heads (on order). Primer black w/black interior.
      1992 Pontiac Trans Am GTA w/SLP Performance Package. Dark Jade Grey Metallic, grey leather, T-Tops.

    7. #7
      Join Date
      Jan 2014
      Posts
      35
      Country Flag: United States
      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.
      Rich
      1962 Mercury Comet, 32V Cobra engine, 5-speed, 8.8 rear, custom suspension
      1965 Ford Mustang, supercharged 5.0 EFI