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2.73 gears

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

  1. codeman

    codeman Registered Member

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    I am close to putting 33's on my 89 Blazer. After reading what some of the codes meant in my glove box, I found out that my Blazer has 2.73 gears. Should I even think about putting bigger tires on with such tall gears? I don't necessarily want to pay all that money to put new gears in. Any suggestions? And what gear is best for 33's. It will mostly be driven on the street.
     
  2. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    well my full size had 33's and I had 3.73. Nice highway gear.. barely ever got stuck...
    then I went to a stick and 4.56's... Hell I could take a mustang 5.0 off the line with my pickup.. /forums/images/icons/wink.gif
    now I am running 40's and havent had it on the road.. /forums/images/icons/frown.gif
    so I would say change the gears definitely...
    also what size tires are stock?
    mustangs have like a 2something gear ratio and they have tiney tires.. ( I only know that cuz I had a friend with a mustang.. I am serious.. Really I am .. umm.. geez.. please believe me... )
     
  3. codeman

    codeman Registered Member

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    Stock tires are 31's.
     
  4. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    I had 2.73s in my '80 when I bought it. WHen I put the 31s on it, it sucked. When I put the 35s on I nearly went crazy. W/33 you will want some lower gears. Are you sure they are not 3.73s? I thought the got rid of the 2.73s when they went to the O/D trans. I don't know why they ever put that high of a gear into a truck.
     
  5. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I used to have a Blazer with 2.73 gears and I installed a 4" lift and some 35" tires.

    Granted, the truck was not that impressive with those gearing, but then again, a 305 engine didn't make things much better either. /forums/images/icons/tongue.gif
     
  6. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    The 350s that they put in the 1980 were rated at 160 HP, so I know your pain. Mine had so little compression I could grab the flexplate and turn it by hand w/o gloves-that's w/ the plugs in!
     
  7. gokartergo

    gokartergo 3/4 ton status Staff Member Moderator

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    I had 3.08's with a 4 in lift and 33's for a very short time.. It sucked.Took me from San Fran. to LA to get up to speed.. That lasted about 2 months and that was with a new 350.. Ithen went to 4.56's..
     
  8. RedDwarf

    RedDwarf 1/2 ton status

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    I know lots of guys with 2.73 gears in 2wd trucks that run 31 - 33" tires. Kinda sucks, but one guy with a 350 and open diff can still do a burnout!!! /forums/images/icons/tongue.gif

    Put on the tires and upgrade the gears when you can. Just keep it in Drive instead of OD
     
  9. wrathORC

    wrathORC 1/2 ton status

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    Hah. At least you've got the fool-injected Blazer. 33's on 2.73s won't be so bad. It won't be great either. 3.73s or 4.11s is best in my opinion.
     
  10. wrathORC

    wrathORC 1/2 ton status

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    I had 2.73s, 31" tires, 700R4 transmission, and a 305. It originally came with 235x75r15s though. It wouldn't go any faster than 60mph in overdrive without the torque converter unlocking with the 235s and barn door aerodynamics. When I put the 31s on I couldn't even get it up to 55mph which is all that it'd hold in overdrive without it shifting all the time on the way up.

    They did all this for gas mileage. It made sense because under normal city driving you'd never notice it. However, the supposed 145 horsepower the 305 made was actually like 125 according to most magazines. I know mine was a gutless wonder. My Sonoma with 2.5L and 31" tires had more guts. And it only made 92 horsepower.

    Now with a 350 in my truck it'll hold 65mph in overdrive as long as I don't have a headwind or more than a 1° grade. After that I have to run it in third gear. But I can get 17mpg on the highway (right around 1300rpm) which is pretty good for a truck with barn door aerodynamics and a carburetor. It's just that the city and the expressway I get around 11mpg.
     
  11. BLUESMAN

    BLUESMAN 1/2 ton status

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    Man those gears are going to suck wind hard with 33's!!Uhh gee just use 1st and 2nd gear,you won't need the other 2 gears.Get 4.10's if you have the TH700 overdrive trans.I used to have a K/5 with 3.08's and 33's....man that bit!!Mike
     
  12. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Wow, they seemed like a bad idea w/o O/D. I know it was suposed to improve MPG but mine got better w/ the 4.56s. I had to floor it just to pull out the driveway before the swap. They may have worked w/ the stock P-metric tires, but they still sucked. Just for a comparsion, my '96 jeep ZJ came stock 3.73s & a 28" tall tire, (318-V8 & O/D trans, too).
     
  13. mpascino

    mpascino 1/2 ton status

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    Stock tires are 235/ 75/ r15 if you check the driver door. Those measure up to 28.9 inches.
    Mike
     
  14. Dunc03

    Dunc03 1/2 ton status

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    I have a 86 with a 305 and 3.42 gears. I just went up to 33 from 31 and it was a big difference. It had a noticable lack ok power on the road not to mention off road. If I got in sand climbing a hill it would not turn the tires in high and it did not turn them well in 4lo. This was thick sand and I was going at it sideways, but still it lackedthe power to make all four tires spin. The front would spin, but the backl just sat still. I'm solving the problem with a 330hp 350, but gear would be a lot cheaper solution for you. I'm like the rest of the guys though, I think you probably have 3.73. 31 inch tires with 2.73 gear would suck unless you had a bad motor. Hope this helps
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    31" was optional

    Sold some 3.73's to a guy with a 700 and 2.73's, with something like 35's on the truck. He just got back from the shop, as he had blown the tranny. IMO if you aren't careful with tires larger than 31" and even 3.08 gears, you are putting a hurt on that 700, as it will spend a LOT of time lugging, and the converter will be generating a LOT of heat in city driving trying to get a 5000lb underpowered vehicle with horrid gears moving.

    I had 3.08's/700R4/305/31's and got WORSE mileage than I do with 3.42's/No OD (SM465)/gear drive transfercase/33" tires and a 350. Not by much, but I exceed the 3.08 combo in city driving by about 3 MPG, and freeway by 1 MPG.
     
  16. bigmack

    bigmack 1/2 ton status

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    When I bought my truck it had 33" tires and 2.73 gears with a stock (weak) 350. It sucked bad, then I went to 3.73 gears and 35" tires and it was much better. The stock 350 was still nutless but the lower gears helped.
     
  17. Blue85

    Blue85 Troll Premium Member

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    Yeah, you should probably recheck the code and also do the count driveshaft and wheel rotation thing or pop the diff cover and count teeth. If it's really 3.73, then that is OK for 33's. No need to spend the money. If it's 2.73, I would swap it even to stay with 31's. The difference between 2.73 and 3.73 is at least as noticeable as the swap from a small block to a big block, but without the drop in gas mileage in this case.

    There are lots of posts dealing with your options for gear/axle swaps.

    How about this: Put on 38's, keep the 2.73's and run in low range all the time! That would be sweet with a twin stick 205. /forums/images/icons/laugh.gif Oh yeah, and a doubler for off-roading.
     
  18. wrathORC

    wrathORC 1/2 ton status

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    Yeah, it does suck. It's hard to keep it out of the secondaries if you want to keep up with traffic after a stop light. I plan on solving the problem by putting 3.73s in the front after I stick my 3.73 equipped 14 bolt under there.
     
  19. HarryH3

    HarryH3 1 ton status Author

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    Put some info in your profile, so folks know where you're located. Someone may have just what you need, just laying around in the garage. I've got two sets of 10-bolts. One set is geared at 3.42's and the other is geared at 3.73. Both have the infamous Gov-Loc rear. I'd make a smokin' deal to someone that could come and pick 'em up. /forums/images/icons/cool.gif
     
  20. NetBlazer

    NetBlazer Registered Member

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    I would definitely not run 33's with 2.73 gears. My 88 also came from the factory with those gears, and even with 31's it was totally gutless and would not hold OD on the highway on even the slightest grade. I upgraded to 3.73's and 33x12.5 and it's so much better now. It will actually move when I step on the gas off the line and I can cruise at 70+ in overdrive with no problems. Do you have the 700R4 (Auto trans with OD) or a standard? If you're worried about the cost of gears, try swallowing the cost of rebuilding the 700R4 beacuse it runs so hot from fighting against the high gearing and constantly swapping in and out of OD /forums/images/icons/shocked.gif
    I got my gears done cheap by swapping out the entire axle rather than buying and having gears installed. Lots of guys here are getting rid of 10bolt axles with 3.73 axles and you can get them cheap. They should hold up just fine for you on the street. I got my set through this board (plug for signing up as a CK5 member /forums/images/icons/wink.gif ) for only $150 and it's an easy swap. In retrospect I kinda wish I had gotten 4.10's as I plan on going to 35's in the future but I was worried that they would be too low with just the 33's, but it would have been fine with the OD trans.

    Good luck!
     

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