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5.13 gears?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by adamcarp, Jan 28, 2001.

  1. adamcarp

    adamcarp Registered Member

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    Location:
    sheridan ca (sacramento)
    I have a 78 balzer with 350/th350 and np203 I am doing a 14 bolt 8lug swap in. has any one ran 5.13 gears
    in their rig if so what was your rpm like on the highway. how about with 4.88 gears. I want to be ables to crawl as low as possible. oh yeah i have 36inch tsl's on it.

    78 blazer
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Location:
    Sioux City, IA, USA
    4.88 would probably be your best bet with the three speed transmission. If you want crawl, use the 4 low. If you were running down the highway in 2H, 3rd gear, at 65 MPH you'd be pulling over 3,100 RPM. With 4.88s you'd be going a more reasonable 2960. If you had 700R4 you'd be running 2179 with 5.13 gears and 2,072 RPM with the 4.88s. If you ran the TH350 with the 5.13 diffs, in first gear you're looking 25.98:1 crawl. With 4.88 gears you'll get 24.72. If you had a TH700R4 you would get 31.55 and 30.01 for the diff ratios just mentioned. If it were me I'd go with the 4.88s and the TH350. It would take some work to get the 700R4 to work and its not that tough. When compared with the 400 the 350 isnt that tough either but its still a great transmission. I think 700R4 gets picked on way too much. The nice thing about it is that it you can run bigger gears it the first gears are actually lower than the 350 or 400.

    June 2001 - The Texas Sawz All masacre begins. Be afraid rust, be very afraid. [​IMG]
     

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