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transmisssion

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by KASS, Apr 24, 2001.

  1. KASS

    KASS Registered Member

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    I have a '88 Blazer w/ 350 TBI and an automatic OD transmission. I unfortunately have to rebuild the tranny before rebuilding the engine. I will be towing a 25' travel trailer that weighs about 5500 lbs on a routine basis. The transmission shop sates that I should add a few things to make the tranny better, just thought I would run it by some of knowledgeable people on this site. Listed are a new torque converter, a 2/4 servo for a corvette, a shift kit, boost valves & sleeves, 3-4 commercial clutch pack, and a rather ambiguous "lube update". Also he prefers to use Amsoil tranny fluid that adds approx. $100 to the rebuild.
    Just thought that I would be able to get some feedback.
    thanks
     
  2. Waxer

    Waxer 1/2 ton status Author

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    I would definitely do the upgrades. I've heard story apon story about the 700r4 failing.
     
  3. moneypit

    moneypit 1/2 ton status

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    Don't forget a MASSIVE cooler!! A temp guage also wouldn't be a bad idea. I have both on mine.
     
  4. Daveytree

    Daveytree Registered Member

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    I would do the rebuild. A 700r4 is a testy tranny. Take it from me. If you read my previouse post called Fire on the Interstate you'll know why. Do the rebuild. This next part is very important, <font color=red>GET A WRITTEN WARRANTY</font color=red>. If you don't you may be very sorry.

    [​IMG]If you don't like my driving, <font color=red> get back on the road.</font color=red> [​IMG]
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I'm not the most knowledgeable guy when it comes to trannies, but I can answer a few of your questions:

    1. Whenever you replace a tranny, you should always use a new torque convertor. As far as I know, most shops INCLUDE one with any rebuild..........

    2. A shift kit is always a good idea. This will speed up and firm up your shifts. The faster your tranny shifts between gears, the cooler it will run.

    3. Amsoil offers top-notch lube products. I'm not sure if it's worth the extra C-note(unless it's synthetic), but if you've got the cash, go for it.

    I would also strongly advise you to install an auxialliary tranny cooler. I went with a 22,000 GVW Tru-Cool made by Long. Go with a rad style cooler as opposed to an aluminum tube-fin design- these are built tougher and offer better cooling.

    FYI- I tow a 3000 lb travel trailer all through the Canadian Rockies and have never had any tranny problems. The 700r4 in my 83 is factory............



    <font color=red>PHOTO ALBUM-</font color=red> <A target="_blank" HREF=http://albums.photopoint.com/j/AlbumList?u=1289798>http://albums.photopoint.com/j/AlbumList?u=1289798</A>.......<font color=blue>TRUCK & HIKING PICS</font color=blue>
     
  6. CaptCrunch

    CaptCrunch 1/2 ton status

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    OK... I have been through this dance a few times... First off skip the vette servo unless they are going to be specfrically modifying your tranny to soften the shift... otherwise the vette servo will make it shift hard and wear the tranny as well despite what they may tell you. The vettes have an aux. valve body that softens this harshness. They have Caprice servos from police packages that I have heard are suppost to be a nice upgrade and not as harsh.
    700's don't need and shouldn't get shift kits. There are modifications that should be done to fix problems with the original design, but a shift kit is not recommended.
    Here is what I recommend after being through quite a few of these and my buddy who is the 700 Guru recommend... 700's are nortorious for burning up the 3/4 clutch packs... some kits slam extra clutches in which can be good, but "alto" kits have very thin clutches and tend to heat up quickly... Actually the whole 3/4 clutch ordeal can be fixed by drilling out the 3rd clutch apply hole... But anyhow find out exactly what is being done modification wise... many shops modify the the tranny to shift faster into 3rd... but don't modify second to release quicker which cause a bind (this is also MAJOR heat... it can feel like a good firm shift or be worse and be a cluck or thud) This will result in the tranny burnning up 2nd... which never happens.
    Things that I'd definetly upgade and make sure they take care of are obvious new Tconverter, GM boost valve, the NEWER design GM pressure regulator valve, also upgrade the sungear shell and input sprag (especially if you plan to stiffen shifts or go vette servo... these are already weak spots in the 700R4 trans and get hammer on w/ these modifications).
    Other then that talk to whoever is going to do the build... find out exactly what he is doing and why? I strongly recommend getting racers and offroaders opinions on tranny guys.... especially ones familar with the 700. Building the 700 up can be a bit trick, but my buddy has a BBC infront of one and it is living great considering the hp he's pushing. Good luck w/ the build... also may want to consider a Jet or TCI built tranny.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  7. Thunder

    Thunder 3/4 ton status

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    Also get a aftermarket pan with a drain plug or install a drain plug in your pan. That way you can change the fluid often. Clean fresh trans fluid wil keep the 700r4 running good for a long time. The biggest problem with the 700r4 is heat and fluid breakdown. This causes lack of lubrication and eventually trans failure.
     
  8. LittleJimmy

    LittleJimmy 1/2 ton status

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    I would also put on a bigger trans pan. I bought a TCI I believe. It is cast aluminum and it has cooling fins and a drain plug. It was about 120.00 bucks but I think it is worth it. And I plan on a tranny cooler later down the road. My truck interior is apart now. But anyway I would look into that. They make tranny pans that are steel to that are just as big but no cooling fins and they still have drain plugs that are a little cheaper. Anyway I would look into it. Later LittleJimmy..
     
  9. Thunder

    Thunder 3/4 ton status

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    Gotta agree with Cptn. crunch. The vett servos and shift kit are not good. espically if you tow. I have a 700r4 with no mods other than the factory upgrades, and added lube. I tow all the time and have had no problems. As has been said in eariler posts Big cooler and Clean fluid are the key to a long lived tranny. I have a drain plug on my pan and usually change my fluid twice a year and use Q state or Valvoline. I also use Trans Cool, it works. If you change fluid often i dont think there is any reason to run amsoil or other expensive racing fluids.
    B&M makes a 700r4 they call the Traveler. It is designed just for light trucks, RVs and towing. You might want to check into that also.
     

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