1978 Trans Am 10 bolt posi questions

Discussion in 'Transmission & Driveline Topics' started by Gasoholic, Feb 8, 2020.

  1. Scaleytail

    Scaleytail Veteran Member

    Messages:
    146
    Likes Received:
    28
    Joined:
    Jun 12, 2016
    Location:
    North Aurora, il
    Had a 2.73 rear end in a 350 auto 78 Camaro. Added the Edelbrock Performer Intake and Cam plus Herman headers and buried the 130 mph needle on the highway. Miss my youth except for the fact I had no brains.
     
    jeff swisher likes this.
  2. 351maverick

    351maverick full time Ebay seller/hustler/car killer

    Messages:
    3,770
    Likes Received:
    516
    Joined:
    Aug 11, 2010
    Location:
    erie, PA
    825 for that junk ratio rear axle is a JOKE

    seller obviously is a clown
     
  3. Burd

    Burd Veteran Member Lifetime Gold Member

    Messages:
    683
    Likes Received:
    131
    Joined:
    Oct 6, 2011
    Location:
    Just off Woodward
    Here are your 1978 Diff’s. image.jpg
     
    Gasoholic likes this.
  4. Gary S

    Gary S Administrator Lifetime Gold Member

    Messages:
    23,441
    Likes Received:
    1,299
    Joined:
    Apr 14, 1999
    Location:
    Bismarck, North Dakota
    Years ago I was looking for a Trans Am posi rear end for my Son's Z28. I found over a dozen of them in the local wrecking yards here, but every one of them was either a 2.41 or a 2.56. He wanted a 3.42. It took a couple of years of looking, but finally I found a 3.42 posi in a junked Z28 for him. It seems that almost all the Trans Ams with automatic trannys got the 2.41 or 2.56 as the Pontiac engines were good engines for torque, but lacked rpm capability. I never did find a Trans Am in my local junkyards with a 4 speed manual that would have had the better ratios.
    A couple of years later there was a rummage sale near my house. The guy had a 3.23 posi from a T/A that he would sell cheap, but by then, we didn't need it.
     
  5. HOGDADDY

    HOGDADDY Veteran Member

    Messages:
    443
    Likes Received:
    24
    Joined:
    Jun 8, 2005
    Location:
    Birmingham,Alabama
    I scored a 3:42 limited slip (posi) from a Trans Am in the late 80's from a salvage yard. The salvage yard told me it wasn't a posi and the price was $100.
    It was a posi : ).
     
  6. BCB57

    BCB57 New Member

    Messages:
    4
    Likes Received:
    1
    Joined:
    May 16, 2017
     
  7. Plant Engineer

    Plant Engineer Veteran Member

    Messages:
    404
    Likes Received:
    108
    Joined:
    May 17, 2017
    Location:
    Fort Mill SC
    I had a 77 T/A that initially had a 400 in it. I blew the engine up when I was 15 and my dad and I went to the junk yard and bought a SD 455 for $400. Those were the days. Threw a different intake on it and an 850 Double Pumper and did a re ring on the engine and a new cam . Threw it in the T/A with its 2.73 gears and I could boil the uniroyal tires off all day long and go 165 MPH. Thanks Dad. Sold the car a few years later for $900 after my '69 Camaro got driveable. Ah, the early 80's.
     
  8. BCB57

    BCB57 New Member

    Messages:
    4
    Likes Received:
    1
    Joined:
    May 16, 2017
    I have a 10 bolt posi from a '71 with 4.11 gears in great shape. I would make you a great deal on it but I think the cost of shipping from Houston to MI would be prohibitive....
     
  9. 70RamAirIII

    70RamAirIII Pontiac-aholic

    Messages:
    62
    Likes Received:
    16
    Joined:
    Jan 10, 2005
    Location:
    Calgary, Alberta
    if my memory serves me, the 403 powered TA's had a 2.73, while the 400 powered TA's had a 3.23 (or maybe in 1978 auto dictated 2.73's!?);
    If it is from a TA, it should be a posi - as this feature came standard with the TA.
    Since the ratio is just that, a ratio, you could have a friend (or maybe the seller) help you guess where about the ratio is;
    have one of the axles slowly turned one full rotation, and count the number of full rotations on the pinion side;
    not quite three rotations of the pinion would be a 2.73;
    nearly three and a half pinion rotations would be 3.23;
    You could also have an aftermarket ring and pinion in there, and hit the jackpot.
     
  10. Plant Engineer

    Plant Engineer Veteran Member

    Messages:
    404
    Likes Received:
    108
    Joined:
    May 17, 2017
    Location:
    Fort Mill SC
    2.73 in in the 400's unless it was the W72 6.6 .
     

Share This Page