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Difference between 305/350 and sm465 tire/gear questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jplagg, Mar 6, 2002.

  1. jplagg

    jplagg Registered Member

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    I am looking at another K5 and the guy said it was a 350 (he hasnt had it that long, but needs to sell due to $ issues. and it was rebuilt before he got it) I looked at the codes in the glove compartment and it said it came with a 5.0L engine - 305 right? so i dont know if the 305 was rebuilt or a 350 was replaced. is there a way to tell by the size of anything on the engine to tell which engine it is? How visable are the engine numbers on the engine while its in the vehicle and where are they? Thanks

    Also, its a sm465 with 10 bolt rear and 3.08 gears. I know larger tires (31s-33s) dont go well with that on an auto, so is that the same with the sm465?

    thanks again
    josh
     
  2. TopOff

    TopOff 1/2 ton status

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    The 350 auto has a 2.73 first gear ( I think) then a final 1:1 3rd gear.

    The sm465 has a 6.5 (or something close) granny, then a final 1:1 3rd gear.

    If you run 33s with 3.08s in your final gear you will be pulling ~2000 rpms at 65mph. This sucks!

    However, with the sm465 if you never use 3rd gear...../forums/images/icons/smile.gif

    I am trying to get rid of my TH350/203 and get a sm465/203 for the low granny! So if anyone has one to sell in the greater Sacramento, CA area LMK. I want the pedals and all the linkage too. /forums/images/icons/smile.gif

    Good luck.
     
  3. Calclips

    Calclips 1/2 ton status

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    SM465 is one VERY VERY tough tranny. I've only heard of a few people ever blowing one of those up... they are super strong. As far as engine ID between 350 and 305, you'd have to look at the casting numbers. Somebody arround here has them because I've asked this one before, sorry I don't remember what they were. All of the accessories for a 350 and 305 are the same... so visually there isn't really a sure-fire way to tell.
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The engine numbers you need are on the passenger side front of the motor in behind the alternator. There is a machined pad with a series of numbers stamped on it. Grab some degreaser and a rag and a flashlight. Once you have the numbers go to www.mortec.com and look em up.

    As for SM465's and bad gearing...at least they will not self destruct like an auto will with tall gears and big tires. My truck came with a SM 465, 2.73 gears and 33" tires. I just used granny to start off and used 4th like an overdrive. It worked out pretty good...

    Rene
     
  5. jplagg

    jplagg Registered Member

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    Edit - Rene cleared it up

    so, 33s and sm465 are ok then? Just making sure i understand /forums/images/icons/smile.gif <L>


    thanks
     
  6. arq

    arq 1/2 ton status

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    yeap, should be ok.

    ARQ.

    forgot to add, i just burned up my th350 running 3.08diff w/33" tires. i'll be swaping a sm465 in there shortly.
     
  7. m j

    m j 1/2 ton status

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    newer chevs have the displacement in litres cast into the block on right side bellhousing boss
     
  8. Big_B_Murphy

    Big_B_Murphy 1/2 ton status

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    I had a 77K10 that I used to tow with a bunch. SM465/205 with 3.08's in the axles. 33 in tires. Never had a problem.

    Another way to look at it is with a 465 you have a 1:1 top gear. With 3.08's you would have about the same final drive ratio as someone who has a th700 with an OD of about .74(or someting like that). And the 465 is much stonger than a th700.
    I only needed to start off in low when I was towing about 3000 or more pounds.
     
  9. BLUESMAN

    BLUESMAN 1/2 ton status

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    I'm gonna do that swap hopefully this weekend.Running 38's with 4.10 geared 3/4 ton diffs.I can't wait to see what "granny" gear feels like compared to the TH350's 1st gear!!!
     

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