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82 Diesel Blazer, auto to SM465 manual conversion, which gear ratio ?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ambritmann, Jul 21, 2002.

  1. ambritmann

    ambritmann Registered Member

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    North Carolina, USA.
    I am giving up with the 700r4 tranny, I've got nothing against it but they just dont last with towing and other assorted abuse. Have bought a complete 79' 1/2 ton pick-up with the SM465/205 tranny set up to transplant into the Blazer. As I am losing the overdrive gear I am trying to figure what will be a good axle ratio to use to keep the engine rpm's sensible on the highway. I am running 31x10.5/15 tyres and have no wish to go any bigger, I would prefer to change the gearing than lift the truck and fit larger tyres. Any advice/suggestions would be appreciated.
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    As its a diesel, your "power band" is going to be different than my gasser, but with 33" tires, and 3.42 gears, the 465 is perfect. Both freeway and city...easily gets to 85 if I have to pass, and it will walk away on flat ground at idle if I release the clutch in 2nd. (using 1,2,3,4 instead of L,1,2,3)

    I'd probably do the same thing again as well...put the BFG AT or MT 33x10.5R15's on the stock wheels, (depending on your use of the truck) and make sure I had 3.42's. I might try 3.23's to see if freeway mileage would increase at all, but they weren't offered in trucks, you'd have to get new gears or some out of a GM car.

    If I wasn't going to switch tire size, I'd be betting a 3.23 ratio would be much more appropriate and better suited to a diesel application. Heck, even the 3.08 ratio probably wouldn't be *too* bad with a diesel, as long as you weren't expecting to take on cars at stoplights.

    Your speedometer will be off unless you swap the axles out of that '79 along with the 465/205, so either swapping gears or changing tire size will necessitate a speedometer correction...

    3.42 axles are very common, and should be quite cheap. (less than $400 for a pair) Buying two complete axles is cheaper than having them re-geared as a matter of fact, unless you do the gear swap yourself.
     
  3. Batmanjr

    Batmanjr 1/2 ton status

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    I agree with Dyeeager,
    I have a diesel with 3:73 with the 700 and have been contimplating going to the 465 for a while.... I was holding onto a set of axles(12&10 Bolt) with 3.07 to compensate the extra low 7:1 first gear in the 465!!! I've decided to go to 3/4 ton axles and don't need the axles anymore. If you're interested, I'm asking $200 + shipping! Sounds to me like you're on the right track!!!!
    /forums/images/icons/cool.gif
     

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