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  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
    1,036
    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
    1,036
    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
    29
    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
    265
    Country Flag: United States
    I also went with DynoTech for my new driveshaft.
    http://www.TheFOAT.com/92GTA
    1969 Pontiac Firebird
    w/BP 461ci stroker kit, 670 heads & XE274H cam. 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