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T700 trans questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by WARP1, Oct 20, 2000.

  1. WARP1

    WARP1 Registered Member

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    Does anyone have this trans? How does its strength compare to the TH350. That's what I have now. Can I tow a car in overdrive with this trans if I gear my axles low enough? I am trying to decide if I should run 4.56 gears, a T700, and 35 inch tires, or 4.11gears, a TH350, and 35 inch tires.
     
  2. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I wouldn't think you would want to tow with the 700 in o/d, no matter what type of modifications you have done with it. The reason for this is the basic design of the o/d gears which can't handle the added stress of heavy loads and the reason the owners manual says to not use o/d when towing. Overall though, I think a properly built 700 is just as strong as the 350 but has several other advantages also. First gear of the 700 is 3.06:1 versus the first gear of 2.5:1 in the 350, plus the 700 has the 0.70:1 overdrive.
    Even with the 4.56 gears, when in overdrive it would be the same as running 3.20:1 rear axle ratio with a non-overdrive transmission (4.56 x 0.70 = 3.20), so you would probably be lugging the engine if you were towing a heavy load. What about running 4.10 gears and the 700, and not using o/d when towing. This would give you the same rpm as if you had the 350 trans but you would also have a much lower first gear for better acceleration. For example, with 4.10 rear axle gears: T700 = 3.06 x 4.10 = 12.5:1 gear, TH350 = 2.5 x 4.10 = 10.2:1 gear. In order to get that low of an overall gear with the 350, you would have to run a rear axle ratio of 5.0:1.
     
  3. ken

    ken 1/2 ton status

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    Stay away from the 700, ESPECIALLY since you will have to convert to it, meaning swap it in. Keep your 350 and never look back!! It'll cost you $1000+ to swap it in, then a rebuild every 40,000 or so will run you $1000+. You be the judge. Just my opinion BASED on being on the FIFTH 700 in my '90 Suburban that DOES NOT TOW A THING AND NEVER HAS!!! (What a junk tranny).

    ken
     
  4. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I still don't see how somebody can burn up a 700r4 every 40,000 miles. How long did the original last? As I've written before, my dad and myself have accumulated over 700,000 miles on seven different trucks equipped with 700r4's and only one failure. At least one early '90's pickup is still running around the area and has over 160,000 miles on the original trans. The vehicles ranged from an '83 S-10 Blazer to an '00 Silverado (4L60E, but same basic transmission). The one failure occurred at only 30,000 miles but was do to a faulty ECM which did not allow the converter to lock up properly and fried the trans. The only vehicle that had regular transmission fluid changes and an aftermarket cooler was my current '90 K5, all the others were work trucks that were used hard and pulled a boat on the weekends.

    I'm sure some people have had legitimate bad luck and lot's of failures with the 700r4, and it's not as tough as the 400, and I'm not trying to pick on anyone....but my favorite is all the people I have seen on this board and around here who say the original trans lasted over 100,000 miles, but the rebuilts only lasted 20,000 miles so therefore the 700r4 must be junk.....but shouldn't that make you question the quality of the shop doing the rebuild??
     
  5. BigJim85

    BigJim85 1/2 ton status

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    My T700 is still running strong after 170,000+ miles. Hasn't failed me yet.

    "I can get us outta this, just gonna take a whole lotta floorin'!"
     
  6. Chewy

    Chewy 1/2 ton status

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    I agree with 6.2Blazer. Go with a 700 and 4.10 gears. This is a great tranny especially if you will be doing a lot of highway driving. The engine will purr at high speeds.

    [​IMG] '87 Beast
    Colorado, USA
     
  7. backlash

    backlash 1/2 ton status

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    Hey Eric,

    Was real happy with mine also ... finally let go at 177,000 miles. Hope I haven't jinxed ya.

    Am dead in the water ... trying to save money for a rebuild.

    Keep takin good care of her.

    Bob
     
  8. getsome

    getsome 1/2 ton status

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    I have a 84 Jimmy with a 350, 35's, and a 700r4 and I wish like hell that the previos owner had installed 4.56 or 4.88 gears. My 4.10 driving around town is terrible do to the rpm drop when it shifts into 4th gear. I don't have a tach but i'd be suprised if it's turning 1200 rpm at 55. Unless I downshift it I can't get out of my own way. If you go with the 700 install 4.56 or 4.88 gears. If you stay with the th350 4.10 should be fine.

    Getsome
     
  9. archer

    archer 1/2 ton status

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    Isn't a t-700 the beefed up 700r4 from jet? I thought it was bullet proof.

    "who dares wins"
     
  10. Executioner

    Executioner 1/2 ton status

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    Hum, you run it in overdrive ?
    Would'nt last long in overdrive.................
    Good luck
     

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