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Rebuilding TH-400...Tips?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Ryan B., Feb 6, 2002.

  1. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Well it's not for the Blazer, my '67 camaro finally burned up the TH-400...
    I ordered the Master Racing Overhaul kit comes with everything you need to rebuild it, and I also ordered up a TCI 400 manual with pictures and diagrams to guide me through the rebuild...

    [​IMG]ARRRGGGHH! minor problem is it looks as though the tranny can't come out unless the engine comes out... the way the cross member is wedged up in between the subframe connectors and the body tub.

    Anyone have some experience rebuilding TH-400's?
    Any tips before I tackle this myself?
    After I get this down I'm gonna rebuild the TH 350 and the NP205 in my K/5 if it isn't all that difficult.[​IMG] With some luck I'll be an auto rebuilding expert...heh.[​IMG]


    [Real Men Don't Care About Gas Mileage Or Rapid Tire Wear!]
    1972 K/5
    Ryan B.
     
  2. mnstr_fx

    mnstr_fx Registered Member

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    A few quick tips regarding 350's and 400's.

    -Get some .005 - .010" shim stock in a roll. Use a section of this to help install your piston seals.
    -Find a nice clean bench and lay out LOTS of news paper. You are going to strewn out alot of little stuff that needs to be kept in order.
    -Find an old wooden engine skid or something to lay the tranny on its back. This helps when doing all the valve body stuff. Also, find some blocks to help hold the tranny on end for "stacking" the guts back in it.

    BTW - 400's are easier than 350's due to that one ring you will find and cuss for an hour and that last piston in the back of the case. Start with the 400, get some confindence then use your patience on the 350.

    76-82 Chevy Pickup / Blazer - K5-K10-K30
    90' TBI
    TH 400
    203 / 205 Doubler
    Dana 60, Corp 14 - 4.88'd - Detroit Locked
     
  3. laketex

    laketex 3/4 ton status

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    man we pulled apart a TH350 to rebuild it one day, looked under the pan at the miles of fluid maze, then pulled the seal off the input shaft and a whole ton of clutches/bearings/ect came sliding out. We just packed it all back in hopefully like it came out, and took it to the tranny shop. That is one thing that I dont care to ever learn to rebuild. I just lack the patience I think!

    Sherman, Tx
    <font color=red>The blazer's almost on the road....anyone got tree fiddy?</font color=red>
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    You'll need a press to get the springs in the clutch drums back together, at least from my experience...if there was an easier way to do it, (besides having the right tools of course) I sure would have liked to know then. TH400 is easier than the TH350 IMO. Amazingly, both the Th400 I learned on, and the next one, both lived. Not sure about the TH350's, although I will say that B&amp;M's instructions for their shift kit sucked. Trans-Go all the way.


    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  5. talison79

    talison79 1/2 ton status

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    You should find a trans place to get your parts, because you will probably need something not in the kit. I had to replace a couple of pressure plates and some other stuff not in the kit. Also that kit may replace your spring plates with an extra clutch plate, put it together and measure the gap, you can get different thickness pressure plates to set the gap instead of using more shims. This may make more sense after you have it apart. Try to find small trans shop, with a tech willing to help you out. When I did my TH350, my first trans rebuild, I found a really cool guy who new his stuff and didn't have a chip on his shoulder, that removed and pressed in the bushings on the input shaft, that I couldn't do myself. I would also take the case to them after you get it stripped down and have them clean it in their parts washer it will save you a lot of time trying to get all the crud off the case. Check all the metal surfaces and smooth any rough areas with 600 paper. I.E. anything turning in contact with a seal or bushing. Also make sure you have your bushings driven in straight, if something doesn't turn right it is probably a bushing cockeyed. After you get it back together, break it in like the book says and after running it on the street, pull the pan to check it and clean off the filter. I was very careful trying to keep paper towel fibers out and still had bunches of crap in mine, this also lets you know if anything catastrophic is going on inside. I used a large plastic tub full of mineral spirits as a wash then blew off the part before coating it with atf. Just take your time, but don't put it off, once you start so its easier to remember all the parts and where they go. Don't force anything it should all go together very smoothly, if it doesn't something is wrong. Don't be intimidated its pretty easy and after you finish you will be an expert from taking it apart and putting it back together so many times. Good luck. By the way I'm not an expert, but I did stay at a Holiday Inn Express once.
    Hope some of this helps.

    Talison79

    A gun in hand, is better than, a cop on the phone.
     
  6. blazbrnc

    blazbrnc 1/2 ton status

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    I feel that the hardest thing about building a tranny at home is not having a way to hold it. Tranny shops have big c-clamps that hold onto the case which then attach to a cadaver (sp?) table. The tranny can then be rotated 360 degrees. You will want the bellhousing pointing towards the sky 80 % percent of the time so figure out a way to securely hold it that way before you even start. After that it's not too bad, just put it together the way you took it apart.

    Thank you......Detroit!
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Good advice, same route I took with a knowledgable guy, at a cool local trans shop. Bushings are a pain to put in without the right tool, I got them all in, but split two of them trying with a block of wood. Some of that stuff would just be better to pay a pro (in other words, someone with the right tools for the job) to do. You'll save yourself time, and money in parts. Kick them $20 to do everything you can't do, which isn't much. BTW, one of those cheapy feeler gauges, with really thin blades, can be used to get the seals to seat.

    Watch out for sharp edges on the aluminum, GM didn't take any time to smooth them out. Produce some nice cuts.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  8. Zepplin

    Zepplin 1/2 ton status

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    I like the Drew &amp; Mike drop! I listen to it everyday at work.

    74 Blazer
    Zepplin
    Check out my Blazer
    <a target="_blank" href=http://community.webshots.com/user/zepplin1976>http://community.webshots.com/user/zepplin1976</a>
     
  9. 85HeartBurb

    85HeartBurb 1/2 ton status

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    i have a th400 in my 88 1-ton i just did about 8000 miles ago still good i used to be scared to but it wasn't that difficult the only special tool I wished i had was the clutch pack allignment tool i dont know how the chevy manual breaks it down but the hummer manual broke it down pretty good maybe i could send you copies??

    NO LOCKER, STOCK GEARS, NO PWR BRAKES, NO POWER STEERING, NO PROBLEM!

    HIT IT FULL CHICKEN!!!!
     
  10. blazbrnc

    blazbrnc 1/2 ton status

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    Thanks man. I only get to listen to them for about an hour every morning (my ride to work). Definately better than what's up north.
    Just so this isn't totally off topic. The only specialized tool you will need besides long screwdriver type prybars is a pump puller. It's basically a long tube with a screw jack on the end. Once you get it open it is a piece of cake.

    Thank you......Detroit!
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    How did you get the springs back in the clutch drums without tools?



    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  12. blazbrnc

    blazbrnc 1/2 ton status

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    C-clamps, vice, prybars. Did it for a living.

    Thank you......Detroit!
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Heh. I was afraid of bending those thin retaining plates if I clamped unevenly. Amazing how you can never find just the right piece to make a tool when you need it in a hurry. : ) Good idea though.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     

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