Results 1 to 6 of 6

Thread: Less RPM at Highway speed?

  1. #1
    Join Date
    Apr 2009
    Location
    Iowa
    Posts
    10

    Question Less RPM at Highway speed?

    My 1970 1300, 304, manual trany at 60 MPH is turning some High RPMS. The days of this truck working hard are long gone, have another truck for that. I want to get less pull your house off the foundation and gain a little more top end. What would be the easiest way to gain a little less RPM at Highway speed? In first gear you can almost get out and walk next to it, top speed in first is about 4 MPH. Different Trans? different grears in the rear end? I want to keep the Manual Trans. What should I be looking for? Where do I look for I.D. for the Trans and the Diff?

  2. #2
    Join Date
    Feb 2009
    Location
    Aiken, SC
    Posts
    2,423

    Default

    The lowest gear ratio available on the D70 is 4.33, if I remember correctly. Somewhere in that ballpark. 4.88 and 5.13 were common. Taller tires or a T34 transmission (5 speed OD) are the only options, unless you get a t-case with an OD. (note: you do not have to have 4x4 to use the t-case. Just the other parts). Atlas makes one with a very low range and an OD.

    The gear ratio is either on the line set ticket, the tag on the differential, or you'll have to do it the hard way, jack up the back end, spin the wheels, and count how many turns it takes to turn the driveshaft one full rotation. Open diffs, double the number of turns of the wheel, just how the gears work. Any kind of positraction, direct ratio.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  3. #3
    Join Date
    Apr 2009
    Location
    Iowa
    Posts
    10

    Default

    This is a one ton dually, 2wd.

  4. #4
    Join Date
    Feb 2009
    Location
    Aiken, SC
    Posts
    2,423

    Default

    Quote Originally Posted by Brad View Post
    This is a one ton dually, 2wd.
    Same thing applies. You can still mount an overdrive behind the transmission. It doesn't have to be a t-case w/od. I just said it "could."

    The 4 speed transmission in the 1970 was a Borg Warner T98. The 5 speeds available were T34 (OD) T35 and T36 (both direct in 5th). The T34 had a funny shift pattern, with gears 2-5 in a W shift pattern, so 4 and 5 are opposite of where you would expect them. All of them have reverse left and back, first left and forward. For hauling, you'd want a t 36, I think with just closer gears than the 4 speed, high and low the same. The T35 just had a really deep granny gear. I never cared for it much. ( I often get the 35 and 36 mixed up, but the details are correct). Anyway, you want a T34 or T434 if you change the transmissions. You will need bell housing and mounting crossmember along with it.

    The final gear ratio on the T34 is .68:1, so you'd get about a 30% reduction in rpms. I saw one for sale in tiffin, ohio last summer for about 600 bucks.
    Allan E.
    Curmudgeon Extraordinaire
    Charter Member, Old Hippie IH Club
    Old fashioned binder freak

  5. #5
    Join Date
    Apr 2009
    Location
    Iowa
    Posts
    10

    Default

    Thank You for the useful information.

  6. #6
    Join Date
    Apr 2009
    Location
    Kingsport, Tennessee
    Posts
    26

    Default

    So can a T-36 be used in a Scout 800A with a T-18 to achive the same results?

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •