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3.73,35's,th700 GOOD OR BAD?????

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by AK-5GUY, Apr 6, 2003.

  1. AK-5GUY

    AK-5GUY Registered Member

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    3.73,35\'s,th700 GOOD OR BAD?????

    I have an 87 K5 with a 350 and am about to put in a 14 ff with 3.73's and hope to run 35 inch tires. I was hoping to get 4.56 gears, but when I opened up the differential, I found the numbers as 45/12 which = 3.73. I was quite dissapointed. Will this combo give me enough power? I will be using as a daily driver, and do mud and some rocks like uwharrie and maybe eventually tellico. Will this work?
    Harrison
     
  2. zakk

    zakk 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    at 65MPH you'll be doing ~1600 RPM's...that is a bit low, IMHO.

    keeping it in 3rd would net ~2300 which is about right. so as long as you don't *have* to have your rig in OD, you'll be fine.

    your crawl is about 60:1 which is decent for about anything.
     
  3. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    It'll be almost a world class dawg. Save up for a gear change. Mileage will be great on the highway, but will lag big time off the line.
     
  4. AK-5GUY

    AK-5GUY Registered Member

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    Now I got to go on the hunt AGAIN for a 14 ff rear and a front. They just need to be in good condition, in my price range, and 4.10 or 4.56. Won't be too hard. I HOPE!!!!
    Harrison
     
  5. BranndonC

    BranndonC 3/4 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    [ QUOTE ]
    It'll be almost a world class dawg. Save up for a gear change. Mileage will be great on the highway, but will lag big time off the line.

    [/ QUOTE ] i mostally agree, i have 35's and 3.73's and an OD tranny and i don't have much power off the line and getting up to freeway speed takes just about all i got, but i'm going to 4.88's in the future.
     
  6. Bubba Ray Boudreaux

    Bubba Ray Boudreaux 1 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    The only benefit I have gained from this setup has been the drop in RPM on the highway; sure makes the Flowmaster One Chamber of Doom muffler quieter. /forums/images/graemlins/thumb.gif
     
  7. Chris_T

    Chris_T 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    I had that same setup and found OD was almost useless on anything except a flat stretch of highway. 4.56 made a huge difference, but you could probably even look at 4.88s with the OD, especially if you ever think of going bigger than 35's. I'm somewhat sorry I didn't
     
  8. zakk

    zakk 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    [ QUOTE ]
    I had that same setup and found OD was almost useless on anything except a flat stretch of highway. 4.56 made a huge difference, but you could probably even look at 4.88s with the OD, especially if you ever think of going bigger than 35's. I'm somewhat sorry I didn't

    [/ QUOTE ]

    with OD, while in the minority, I believe 5.13's are the way to go, especailly if you see yourself ending up at the 37" tire. the OD does alot to save the deep gearing, but the performance advantage is huge.
     
  9. scrappyk5

    scrappyk5 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    i agree with you guys on this to a point.
    i plan on going up in gear size myself .

    buuut i dont consider it being dawged out.
    i have a 84 k5 with a 87 305 motor using a the
    carb system instead of the tbi. i have the 700r4
    tranny and i am running 35s (34.5")with 3.73's and i move
    along pretty good. i run 65-70 down the hwy to
    work each day, even with a couple co-workers when
    its my turn to commute. i am not even bearing down on it.

    dont get me wrong, its better to get higher gearing ,
    i am just saying that i dont see as much bogging as
    being stated. i guess i am lucky .
     
  10. 1Blazin71

    1Blazin71 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    I actually ran this combo for a while. Hated it. It wasnt bad off the line and around town...that 3.06 1st gear helps...but then I do have a ZZ4 under the hood too.

    The real problem with the 700/3.73s/35"s happens with lockup. You really DO want lockup in 3rd in 4th gear to prevent heat build up when cruising.

    With the 3.73s I was turning WAY to few RPMS to have any power in lockup. It would lockup fine but the tranny would lug the engine which was only spinning at like 1600 RPM, and I'd get horrible accel and even some spark knock when trying to accel on the highway with lockup on. That had me using 3rd and 4th without lockup to cruise and that made LOTS of heat...I'd see 240 deg after pulling a modest hill.

    I switched to 4.56 and it's great. Could have gone 4.88 but elected not to as I kept the D44 up front and was concerned about the 4.88 ring getting a little thin.
     
  11. Chris_T

    Chris_T 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    [ QUOTE ]
    With the 3.73s I was turning WAY to few RPMS to have any power in lockup. It would lockup fine but the tranny would lug the engine which was only spinning at like 1600 RPM, and I'd get horrible accel and even some spark knock when trying to accel on the highway with lockup on. That had me using 3rd and 4th without lockup to cruise and that made LOTS of heat...I'd see 240 deg after pulling a modest hill.

    [/ QUOTE ]

    That was my experience as well. Having a manually switched convertor helped on short hills, as did shifting down to 3rd (My 700 does not lock up in 3rd), but it was a short term fix and I always tried to lock up in OD to avoid heat. And when I got into a strong headwind, or into the mountains - forget about using 4th for anything except going downhill.
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    I had 4.10s, a 700, and 35s and I hated it. It was good about 80% of the time, but you had to cruise pretty fast on the highway in case you hit even a mild hill. 4.56 would be the minimum I'd go in hindsight. 5.13 would be really nice.

    I have yet to ever hear someone complain about too much gear. Everyone only complains about not enough. Go low or go home!
     
  13. zakk

    zakk 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    [ QUOTE ]
    Go low or go home!

    [/ QUOTE ]

    that is right up there with my "If it doesn't Crawl, it belongs at the mall!"

    good one, and speak the truth! /forums/images/graemlins/thumb.gif
     
  14. wrathORC

    wrathORC 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    There is a such thing as too much for highway driving.

    Try 245x50r15s with 4.10s and a TH475. She'll get you to the eighth mile mark pretty darn quick (and about the first forty yards sideways if you want) but at 60mph down the road it tries to rattle your teeth out. /forums/images/graemlins/grin.gif
     
  15. Me89'Jimmy

    Me89'Jimmy 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    i wouldnt risk running stock gears with 35s, i upped my ratio from 3.73 to 4.88 just for the tires. /forums/images/graemlins/k5.gif
     
  16. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    [ QUOTE ]
    There is a such thing as too much for highway driving.

    Try 245x50r15s with 4.10s and a TH475. She'll get you to the eighth mile mark pretty darn quick (and about the first forty yards sideways if you want) but at 60mph down the road it tries to rattle your teeth out. /forums/images/graemlins/grin.gif

    [/ QUOTE ]

    That's without overdrive. I agree with you. My C30 has 4.10s, a TH 400, and 265/75R16s, and that's too much gear unless its heavily loaded, in that case, it's not enough. Overdrive is the ticket. When loaded, it'd have a good gear for power. Unloaded, it'd have a good cruise RPM in overdrive.

    For trucks, I think this is the best use of overdrive. Over gear them, and use overdrive to make up the difference. Under-geared, lugging trucks with OD get crappy mileage anyway, especially around town. More gear will help tremendously.

    I don't know why the factory is so afraid to gear a truck the way it should be geared.
     
  17. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    answer: yes, it will literally "work"... no, it isn't a recommended long-term gearing for 35s... for the above listed reasons.

    j
     
  18. wrathORC

    wrathORC 1/2 ton status

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    Yeah, but 2200rpm is about perfect in my opinion. But it's hard to get that. If I were to run 33s all year round I'd buy me some 4.56s if I couldn't find some used 4.10s. However, I run 235s in the winter time to make navigation a little more easy. 235s, even with a 700R4, would suck on the expressway with 4.56s.

    My truck came with 2.73s and a 700R4... and it has the plow package from the factory. What the... were they thinkin'? It'd be fine if it had a bigblock but we're talkin' about a 305 here.

    2.73s, 33s, and a 700R4 does suck. I think 3.73s would be perfect in my situation (running both 235s and 33s depending on time of year) but even 4.10s would be fine. However, I bought a pair of neglected axles with 3.42s. So far they have been a pain in the butt (ruined carrier, rusted on manual lockouts, et cetera) but I think 3.42s will be livable. 2.73s and 3.08s are unbearable though.

    I don't know what GM was thinking. I know they had to keep their fleet mileage up but this was a bad idea. The only time my truck handles 2.73s and 235s in overdrive is with no wind and perfectly flat. And I've got a well warmed-over 315 under the hood.
     
  19. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    My truck came with 2.73s too.

    I've got a wild idea. Ditch your 235s permenantly and buy some 33x10.50 BFG All-Terrains. They're not quite as skinny as your 235s, but they'll work well in the snow. You can run 4.56s all year round too and not have your engine screaming.

    I think ideal cruise RPM is 2400-2600 even on a stock engine. When these trucks get lifted, they certainly are like pushing a brick through the air.

    My truck runs 2700 @ 55 and 2900 @ 65 which is a little too much, but its got good power. Pretty soon I'll be swapping in a 350 and putting 39.5" Swampers on it. That may put me a little low on cruise RPM, but it'll be sufficient. If I decide that I like having tires that big (which I'm pretty sure I will) the future 1 ton axle swap with 4.88s or 5.13s will be in order. But for now, I think that without overdrive, 4.10s will pull tires that big, just not be ideal.
     
  20. big75jimmy

    big75jimmy Registered Member

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    Re: 3.73,35\'s,th700 GOOD OR BAD?????

    On my '85 I am running 35" Boggers and 3.08 gears with a turbo 400/Np203 and it sucks. Not much acceleration but the top end is alot better. I actually passed my buddy's V-8 Dakota at over 100 mph! I will be swapping to 3/4 ton axles with 4.10s soon.
     

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