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diesel + 700r4, not good?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 93turbo5oh, Dec 31, 2001.

  1. 93turbo5oh

    93turbo5oh Newbie

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    the 1-2 shift in my blazer has started slipping lately. i had the trans rebuild by my local trans guy that built the trans (c4) in the mustang (both the 700 and the c4 are about 3 years old) . the c4 trans has held up, he said the 700s just get soft and wear out. right now the truck has 3.08s in it. i've been thinking of either keeping the 3.08s and putting a th400 (but i cant find a trans to transfer case adapter, but thats another story) or putting 3.73s in and keeping the 700. i have 31" tires on it. please give me your opinions. thanks.

    93 mustang gt- turbo technology street kit 440 rear wheel hp
    82 k5, 6.2 diesel, 4x4, banks sidewinder turbo kit- enough power to tow the mustang.
     
  2. Oblin Goblin

    Oblin Goblin 1/2 ton status

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    Not good. My 700r4 lasted about 10,000 miles with a turbo on my diesel before the converter seized up. Only 30,000 miles on an Aamco rebuild. They said there was a "50% chance" that the transmission was damaged too and need to be rebuilt again. I didn't like those odds so I had a nv4500 swaped in. I thought about going with a th400 but I really wanted a manual tranny and I didn't want to lose overdrive. With a 3.08 rear a th400 might be easier to live with though, especially if you use it mostly for towing.
    My original 700r4 was rebuilt because it was doing the exact same thing yours is.

    Good luck
     
  3. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    700r4 and Diesel do not mix. Let me rephrase that...700r4 and (insert engine here) do not work. They will break down alot faster behind the Diesel because of the low end torque. Get the manual and never worry about it again. I have had 2 700r4s and they are both going to the can....need money for and upgrade.


    SK-15
    J**P...it's whats for dinner!
    Roads? Where we're going, we don't need any roads!
    If it wasn't for bad luck I would have no luck at all!!
     
  4. Danno

    Danno 1/2 ton status

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    If you have to have your 700R4 rebuilt, definately spend the extra money and have it done RIGHT. If you don't, you'll be having it rebuilt again and again.

    I've got my original 700R4 that now has ~200,000 miles on it behind my diesel. It was rebuilt/freshened up about 30,000 miles ago, and still works very well. Fluid and filter changes are almost a religious thing for my K5, and I'm sure that's helped keep the tranny going after all this time.

    If you want to keep the 700R4, and are going to stick with 31" tires, I'd suggest going to 4.10:1 gears in your axles. This will allow your tranny to not constantly have to shift between gears at lower speeds, and should still run a reasonable RPM at highway speeds. Also install an external tranny cooler.

    Buy the 4.10s to keep your 700R4 from burning up, then save up for an NV4500. The 4.10s will be a good match to the NV4500 with your tires, I believe, and should give pretty decent crawling ratios.

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  5. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    Dang, 200,000 miles?!?!? Wish mine would see that!!

    SK-15
    J**P...it's whats for dinner!
    Roads? Where we're going, we don't need any roads!
    If it wasn't for bad luck I would have no luck at all!!
     
  6. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I've got around 110,000 miles on the 700r4 in my '90 with the 6.2 and it still shifts just fine.

    A couple of questions for you:
    - How many miles were on the 700r4 when you had it rebuilt the first time?
    - How many miles are on it since the rebuild?
    - Did the tranny shop install a new torque converter?
    - Did they make sure the lock-up function of the converter was working?
    - Did they make sure the T.V. (throttle valve) cable was properly adjusted?
    - Did they flush out the cooler and lines?
    - Do you keep the trans in Drive when towing?

    I've heard a lot of guys who had the original 700r4 last well over 100,000 miles and then the rebuilt one only lasts 20,000 miles.......that should tell you that the shop didn't do a very good job. If the shop did not replace the converter and it isn't functioning correctly, it will cause excessive heat build-up. A misadjusted TV cable can cause sloppy shifts and therefore heat. If they didn't flush out the lines there is probably left over debris from the original trans that got sucked through the new trans. Towing a car and trailer with the trans in overdrive, especially with 3.08 gears, will cause a lot shifting and again heat buildup.
     
  7. Blue85

    Blue85 Troll Premium Member

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    The low end torque of the 6.2 was hard on the 700 to begin with. Now you've gone to forced induction, which is going to make it a lot worse. Plus, your k5 is an 82, which came with the weaker early 700 that earned it a poor reputation. If you got 3 years on an 82 700R-4 with a turbo 6.2, you should consider yourself lucky.

    If you want the OD, try a raptor, B&M or some other "built" 700. You are well over the stock torque capacity, I'm sure. By all means keep the tranny out of OD when towing and of course use a big oil cooler.

    As for gears, 3.08's aren't terrible with 31's. I would probably keep them. 3.73's would get you a lot of low end power and would give the tranny an easier life. 3.42's aren't enough of a change to warrant the cost. As for the suggestion to go to 4.10's, that seems too low to me, unless you are planning on bigger tires later. When choosing a gear ratio, keep in mind that you shouldn't tow in OD with a 700.

    <font color=green>Today's Forecast: Partly cloudy with a chance of mud</font color=green>
     
  8. 90K5

    90K5 1/2 ton status

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    4.10's will be way too low for 31's. they are too low for me and I have 33's. Get the 700 rebuilt by a good shop that knows what they are doing, and it will alst a long time.

    90K5
     

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