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were to find gear ratio...HELP!!!

Discussion in 'The Garage' started by twoslo4five0, Jan 30, 2007.

  1. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    I know this may be a dumb question and i serched but couldnt find an anwser...i wanna find out my gear ratio in my truck...its an 87 3/4 ton burb...10 bolt 8 lug,14bsf...any ideas..i know about jacking it up and counting the tire rotation to driveshaft rotation but you usually need 2 people...were would it be stameped or tagged on the rears...i really dont wanna have to pull the covers...any one have any insight...
     
  2. sandawgk5

    sandawgk5 3/4 ton status

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    Jack up one wheel, put a paint mark on your driveshaft so you can see it from out side, turn your tire 1 revolution and count the number of times your driveshaft turns. If it is open you then divide that number by 2. If it is locked you need to raise both tires.

    Almost forgot you need to block the wheels and have the Tcase in Neutral.

    Sometimes there is a tag on one of the cover bolts but those usually get torn off. The only other way is to pull the cover and read the numbers stamped on the ring gear.

    Ira
     
  3. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    thoose are the only to ways...thats sucks...i didnt know if it was located on the truck...i know it all has to do with options...but the reason i the reason im trying to find out is for towing...i thought it had a 410s but the thing feels like a dog...i need to know so i can fiqure what gear i wanna go to...the truck has 35s and the motor runs good just really weak..think it needs more gear...
     
  4. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    in an ideal world it would be stamped into a tag that would be bolted to your dif by one of the cover bolts.

    but you may need to pop a cover to be exact. I bought a set of axles that a guy told me were 4.10's. they came with a running truck attached to them. we jacked the rear and used the very scientific method of rotating the tires. It had a gov-loc. "yep looks like a 4.10 to me, how bout you other friend who has also been drinking for several hours." "yup" ok we'll take it.

    we got it home to find out it had 3.73 gears.

    on a side note we were drinking because we were staying at Englishtown's spring swap meet and never left the track for 4 days. the truck did mean smokey burnout's. the Englishtown swap meets are an experience if you have never been there. the party never ends, at least till sunday evening.
     
  5. sandawgk5

    sandawgk5 3/4 ton status

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    If you have your RPO code sheet It is on there.

    Ira
     
  6. sandawgk5

    sandawgk5 3/4 ton status

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  7. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    not always. I pulled one out of a junkyard truck the other day. all it said was standard gear. didn't have the tags on the axle and the covers looked like they were off before, they had gasket maker oozing out the sides.

    the only way to know for sure is to read the stamping on the gears/count teeth.
     
  8. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    the truck has a gov lock in it it think...it will spin both in dirt..not on alsphalt though..
     
  9. sandawgk5

    sandawgk5 3/4 ton status

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    Not necesarily a govlock. Is this the original axle for the truck?

    Ira
     
  10. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    yep sure is...
     
  11. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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  12. sandawgk5

    sandawgk5 3/4 ton status

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    Those are the option codes for GM. If you find your RPO code list for your truck you can compare the individual codes to that website and it will tell you what you have. Unless you get lucky and it says standard ratio.

    You may have 3.73 in that thing if it as much of a dog as you think. I have 4.10s and 37s and it is fine if I stay out of OD when not on the Highway.

    Ira
     
  13. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    mine doent have od it has a 400...i dont have the code list...
     
  14. sandawgk5

    sandawgk5 3/4 ton status

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    You know this for sure? It would be either in your glove box door or on the drivers inner fender inside the engine compartment.
    Not doubting just making sure before you give up.

    Then you have to pull the covers or count rotations. I would say pull the covers it will give you an excuse to change the fluid and tell you if you have a gov-loc or what. They do make LS difs for the 14SF ROZ has one in his.

    Ira
     
  15. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    yeah your right..i will look in the truck later its dark now..prolly just end up doing it the hard way...i was thinking it had 410 cause it had a turbo 400 mabye a towing option chevy produced in the past didnt know if anyone elce had the same truck and knew theres thats all...well know what im doing this weekend...
     
  16. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    thanks alot sandawgk5 you were very helpfull!!!
     
  17. diesel4me

    diesel4me 1 ton status Premium Member

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    another way (maybe)...

    GM did stamp "axle codes" into the tubes somewhere--a 3 letter code like "TGF" for example..the parts books at dealers have the codes listed by year and ratio..they claim they stamp the codes in the right upper axle tube,but I've had to wire brush the entire axle housing to find some a few times,they are not always stamped in the place they tell you to look!..and they didn't stamp them too deep,so many times if the axle is real rusty,they are long gone..but you might get lucky and find the code,and then a GM dealer can tell you what year,and what it has for gears (or HAD when it left the factory,at least!)...:crazy:
     
  18. sandawgk5

    sandawgk5 3/4 ton status

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    So what did you find out?

    Ira
     
  19. YZEATER

    YZEATER 1/2 ton status

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    just jack it up, it's not that hard and takes less then 5 minutes.
     
  20. twoslo4five0

    twoslo4five0 3/4 ton status Premium Member GMOTM Winner

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    i havnt done anything yet...but i prolly will this weekend...
     

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