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Let's play "guess the gear ratio"

Discussion in 'The Garage' started by mountainexplorer, Dec 11, 2004.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    From the factory, what would you most likely think the axle gear ratio would be in a:

    1986 Chevy 1-ton 4x4 Crew Cab SRW with a 6.2 Diesel, TH400 and NP205.

    My guess would be 4.10.
    4.56 would be too low for a Diesel. But did they put 3.73's in them also?
     
  2. readymix

    readymix 3/4 ton status

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    I'll guess 4.10:1

    Or more likely 3.73:1
     
  3. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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  4. 84_Chevy_K10

    84_Chevy_K10 Banned

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  5. mountainexplorer

    mountainexplorer 1/2 ton status

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    Thats what the guy who own it thinks too. I had an '83 factory 6.2 1-ton that had 4.10s, but wasn't sure if they had many 3.73 60 fronts in the diesels as well. Makes sense though. He says the truck gets 19mpg too.
     
  6. diesel4me

    diesel4me 1 ton status Premium Member

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    I havent checked my diesel's gear ratio's yet--I'm guessing it has 3.73's,because it seems higher geared than my 74 K20 with 4.10's and the same size tires--the diesel trucks probably are more likely to have a higher ratio(like 3.42 or 3.73 vs 4.10 or 4.56's)due to the lower rpm torque of the diesel--but any ratio can probably be special ordered I suppose.....Someday I'll pull the cover and change the lube,and "de-code" it..
     
  7. blazd88

    blazd88 1/2 ton status

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    iv got one for you!
    1979 1 ton dana60/14ff. it has a 292 straight six,sm465,205tc
    it was a telephone line companys truck so it has a utility bed with a large hydrolic arm in the bed.
    WHATS THE RATIO?
     
  8. atho

    atho 1/2 ton status

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    4.56
     
  9. mountainexplorer

    mountainexplorer 1/2 ton status

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    I'd also guess 4.56 as the ratio from the factory on that 6 cylinder 1-ton.
     
  10. diesel4me

    diesel4me 1 ton status Premium Member

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    Hmm---phone company truck huh?? ---I've seen some 80's vintage 1/2 ton 2wd phone CO.trucks with 2.56 rear axle gears and a wimpy 5 speed like a chevy monza used in the 70's--so in a one ton 4x4 its a wild guess,but I'm going to say its probably a higher ratio more than a low one,maybe 4.10's or even 3.73's if they had them available in a one ton--seems the phone companies around here thought high axle ratio's would give better fuel mileage--I bet they were wrong!!..

    Or maybe someone with a brain had the truck equipped with a nice low gear like 5.13's or even 6.17's--I've seen electric company bucket trucks with 4wd and dana axles set up for off road use--my friends brother drives a similar rig with an auger for installing telephone poles,his had a 366 with a 5 speed,but it was a 60 series truck,with REAL low gears--topped out at 55mph when the govenor kicked in......
     
  11. tarussell

    tarussell 1/2 ton status

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    Between myself and a few buddies we have purchased several K-20 and K-30 trucks with 292's in them and so far all of them have been 4.56 geared trucks .
    the trucks were as follows:
    1978 K-20 292 465/205 Dana 44 / 14FF open 4.56's
    1978 K-30 Cab Chassis 292 465/205 Dana 60/14FF open 4.56's
    1979 K-30 Crew Cab 292 TH400/203 Dana 60/14FF open 4.56's

    As for the original topic my vote is 4.10's !
    The early N/A 6.2's were not real hot performers and needed a little help in the gear department and as for my expirience 4.10 is very common in the 1 Ton applications - that being said it could have been ordered with 3.73 / 4.10 or 4.56's .
    Tom
     
  12. westtexask5

    westtexask5 Registered Member

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    is there any way that it could be a real low ratio like 2.56 or so?
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Nope, D60s don't go that high. That's why the D61 exists, and GM never used it AFAIK.
     
  14. mountainexplorer

    mountainexplorer 1/2 ton status

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    Got another one for everyone:

    1979 Chevy K10 1/2 ton 4x4, 292 6-Cylinder, 4spd/205, 12 bolt rear, 10 bolt front.
     
  15. atho

    atho 1/2 ton status

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    Hmm..3.73
     
  16. mtn. burb

    mtn. burb 1/2 ton status

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    4.56:1


    All the military K30's had'em.
     
  17. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

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    For the original question, my guess is for 3.42's or 3.73.

    For that, I say 3.73's. Was there ever a factory 4.10 12b?
     
  18. tarussell

    tarussell 1/2 ton status

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    As for the 1979 half ton truck I would guess a 4.10 gear .

    Tom
     
  19. mountainexplorer

    mountainexplorer 1/2 ton status

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    I was given a '76 rolling frame once that looked like it had a 4spd and 203 combo originally... wasn't sure on the motor, but it was a 1/2 ton and had 4.10 gears in a 12 bolt and Dana 44.

    The '79 I got was a factory 6-cylinder 1/2 ton 4x4 truck. When I got it, someone had already swapped a 14 bolt under the rear, but the front was still a 6-lug 10-bolt. I still havent actually pulled covers, but I was assuming 4.10s on that one.
     
  20. Tuff84blaze

    Tuff84blaze 1/2 ton status

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    MountainExplorer I have a question for you thats kind of related to this topic, where would you recomend somebody from the Spokane area go to have a set of front and rear gears installed on a 10 bolt front 14 sf rear, and about how much should I expect to pay?

    Thanks.
     

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