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tranny rebuild update and question(s)

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by ed rex, Feb 7, 2002.

  1. ed rex

    ed rex Registered Member

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    So, finished up with rebuilding my TH350. My overall impression was that this was a 'cakewalk'. Not a quick cakewalk, but rather a meticulous, by the numbers learning process.

    I started with the B&M transkit.....about $214. Let me just say that a more detailed set of procedures you will never find. Step by step, the instructions leave very little to interpretation. This was the first transmission rebuild I have attempted and it was like the instructions were written specifically for a 'first timer'. I encountered no problems to speak of and would highly recommend to anyone who want to 'do it yourself' to save some $$. In all honesty, it was more of a PITA to remove and re-install than to rebuild. If you can remove and re-install, you should have no problem rebuilding.

    Took me about 30 hours total from turning off the truck in the garage to turning on the key to restart it. I can envision that this time be cut in half if you've done it once, but I wanted to take my time and get it right.

    Tools - No special tools required other than something to compress clutch springs to get to keeper rings. Most times I encountered this dual C-clamps worked excellent. However, the last 'clutch pack' is intregal to the bottom or rear of the tranny and requires some creative energy to resolve. For me, resolution was in the form of an old steering wheel spring plate compressor tool, but really two pieces of metal and a bolt would work as well. I would also recommend a good 'pick set' for removal of numerous snap rings.

    While the instructions were very good, I would suggest that you lay the parts you remove during the course of disassembly out in order. One thing that the instructions direct you to do is to put all the parts in the (cleaned out) tranny pan so's they don't get lost. That's cool but I found the ensuing scrambled mess to be a little confusing upon re-assembly. The only other improvement to the instructions I could see would be to label the parts in the kit. Sometimes it would say 'replace o-ring with one supplied' and you'd go to the o-ring bag to find 15 o-rings that are similar in size.

    One of the final steps eludes to checking shaft end play. There is some confusion as to the specs here. Instructions read .015 to .030 end play while the transmission repair shops I visited to get shims told me anywhere betweem .050 and .100. I shimmed mine to .050.

    After re-installing the tranny and transfer case, I hooked up the rear drive shaft and took her for a spin. Worked great. Better than I have had it working ever. I opted for the 'heavy duty' option while rebuilding. The kit comes with three options, heavy duty, street/competition, and full out racing. The heavy duty has a very solid feel to it however, it also shifts too soon. Shifts at about 2000RPM.

    I would like it to wind out to about 2500 - 2800 before shifting. How do I increase the shift points? Is this a function of the vacuum modulator? Of the governer? Of something else? If I swap out the stock vacuum modulator in favor of a B&M adjustable modulator, will this solve my problem? Someone told me that the big block creates excessive vacuum and causes the truck to shift early. Previously, I could not start the truck in Drive because it would almost immediately click up into drive. All these years I've been starting from a stop in 2nd and shifting into drive when the desired RPM's are achieved. I also do not have the 'kickdown' or 'passing gear' throttle linkage connected. This due to the fact that there was previously a Holly 650 double pumper on a torker manifold and I guess that 1. the holly didn't have a spot for the cable to connect to and 2. the torker is 'twisted' making the distance too long for the cable. I have since put a Holly 600 single pump on which has a place for the kickdown cable, and I have lengthened the cable and intend to hook that up tonight. Does this have squat to do with the shift points or is this solely for downshifting under full or almost full throttle conditions?

    Thanks!
     
  2. Triaged

    Triaged 1/2 ton status

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    I have heard that the modulator is good for only a few MPH of adjustment (kind of a fine tune) and that the governer is what will make big changes. I have the opposit problem with my trans...if I keep my foot to the floor it will never shift. I need to start playing with it but because I hardly ever use WOT I have just left it.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
    <a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>
     
  3. BARRAZA

    BARRAZA 1/2 ton status

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    Congrats on your first tranny rebuild. My first (25yrs ago) didn't go as well.
    I would still recommend someone doing a rebuild get a good book, the one I referenced in the post about the thrust washer makes the B&amp;M instructions look like notes scratched on a bar napkin.
    As for the thrust washer, the B&amp;M instructions are not "wrong" but they are not very clear either. The clearances they recommend are "blueprint" tolerances for a racing trans. As you have seen, a trans will usually work fine if the clearances are not perfect, but I bet that the ones B&amp;M builds are right on the money. Turbo 350's are hard on bushings and excess front end play makes thing worse. In fact the change that GM made to the thrust washer when they changed it to a Torrington type bearing were directly related to the front end play issue. BTW the reason that the thrust washer is considered better for HP applications is that the torrington bearing could break under extreme shock loading, imagine those little bearings floating around in there!
    The modulator, governor, and kickdown cable all contribute to proper shifting. The trans WILL NOT shift properly at part throttle without the cable connected and adjusted. The governor is mostly effective for WOT shift points, the modulator adjusts line pressures in relationship to load and the cable attached to the throttle effects part throttle shifts and kickdowns. Hook up the cable and everything should be fine
     
  4. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Sweet. Good to read this stuff!!! Thanks for taking the time to write up your experience and knowledge to help people like me out... I'm gonna start my auto rebuild tommorow! After you said it isn't that difficult to rebuild an auto tranny ... I've been thinking eventually I want to rebuild the TH-350 and NP205 in my blazer...
    And then last weekend the TH-400 in my '67 Camaro started slipping bad in 3rd and then 2nd, until there was no 2nd or 3rd by the time i got home a couple blocks... and no reverse either... I'm thinking the clutches are burned.

    I already borrowed the clutch hub compressor tool, you were talking about... The dude I bought the camaro from loaned me some tools I'll need, but don't have yet.

    I got the B&amp;M master racing overhaul kit with their "high performance" clutches and bands etc. Didn't come with any directions like the trans kit you're talking about....
    But I ordered a TCI TH-400 complete rebuild manual from Jeg's. Looks very good and there are exploded views of all the parts so I don't think there should be much confusion.

    I'm also going to dedicate the entire garage floor covered with newspaper or cardboard boxes to keep everything in order and hopefully less confusing. I have a bench but don't know how well the tranny will stay put up on the bench...
    Anyone have any good ideas how to position the tranny... wood blocks?

    I'm planning on taking pic's of the rebuild and maybe in a week or two I'll have a write up of my experience rebuilding an auto. [​IMG]

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

    ed rex Registered Member

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    Barraza - thanks for the additional info! I'll have to score that reference book as I am hard pressed to imagine a more thorough instruction set. The thing I like about the B&amp;M instructions was the step-by-step nature that appeared to really target the first time 'do it yourselfer'.

    Additionally, I went ahead and ordered both an adjustable govner and an adjustable vacuum modulator! Should be able to raise the shift point now. I also hooked up the detent cable so the passing gear/kickdown is working properly but alas, it made no noticeable diff in the shift point.

    Ryan - Good luck with your rebuild. The one thing I forgot to mention and you covered was the need to spread out paper/cardboard. I used a series of several large moving boxes flattened open and still have a mess to clean up. I can assure you that this is one messy job!!! Cleaning parts was most certainly one of the biggest pains of the whole episode. I would recommend to all to invest in a $10 box of 100 latex 'examination' gloves. The tranny fluid will eventually break the rubber down, but it takes a few hours and by then you would have ripped them open anyways and have moved on to a fresh pair. These things definately save your hands from unnecessary and excessive chemical onslaught.

    What I did as far as 'where to put it' was to put it with the output shaft facing downwards and resting between two pieces of 2x6's, sitting on a stool with the tranny between legs just start 'emptying the bucket' so to speak. Actually, with the transfer case, torque converter and oil pump removed, the tranny is fairly light. Certainly manageable.

    Later.
     
  6. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Thanks ed rex.
    It really isn't that difficult at all.
    I tore into it, and found the clutches were all burnt up. I have it mostly all back together now, but I am now where you were at...
    I have to go to a local tranny shop and get a thrust wahser for the front endplay.

    In the manual I have... when you first examine the TH-400 before you take anything apart, you're supposed to measure the endplay of the input and ouput shaft. The output on mine was within spec (something like .007" - .019")

    Now I have it back together, The rear endplay is still good (about .015). The front is now too tight and won't spin the input shaft when you start to tighten it up because there are all new thicker clutch packs installed.
    The thrust washer i have now is .108" and I need to go down to about an .082 -.086" thrust washer. Can't wait to get it back in and see how it runs!

    Is this .050" - .100" you are talking about for the input or output shaft endplay? I would like it to be a little tighter then the original .050" felt. Besides this is going to have to handle a 520HP 530ft.lbs. engine so my tranny rebuild will be put to the test. [​IMG][​IMG] I will start a new thread when I get this completly finished and do a little write up as well on my experience. I took some
    <a target="_blank" href=http://communities.msn.com/Ryans1972Blazer/th400transmissionrebuild.msnw>Pictures</a> and I still have more to add.

    Now I'm wondering, seeing how badly toasted those clutches for 3rd gear were... If that could have affected my chassis dyno! Maybe that was slipping a month ago on the dyno. only one way to know...

    Thanks for the help!

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

    ed rex Registered Member

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    Ryan, you might want to pull that last clutch pak out and really verify that all the clutches and steel plates clicked down. When I first performed the end play check, my input shaft would not spin with the oil pump installed. I had a bit of a struggle coaxing that last clutch disk to line up. 4 out of 5 did but man o man, that 5th one gave me heartburn! Grabbing the input shaft, I twisted, shook and jiggled that assembly until FINALLY the damn thing popped into place. Don't know why it was such a pain, all the others went really smooth. The fortunate part was that it was the last item before checking end play so I didn't have to do any disassembly.

    I think I read that the TH400 is much more tight in end play tolerance than the TH350. The dude at the tranny shop that sported me shims warned that on a 350, you do not want to go too tight otherwise you run the risk of excellerated disk burnout. With that in mind, I would try and stay within the guidelines.
     
  8. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    DDOOOAAAAAHHHH! Thanks for pointing it out to me now. I just got it figured out.
    Your right. I had all 5 clutches lined up, and the three below that, but for some reason it wasn't dropping all the way down... Only needed a little more space to make it to where it could turn and be within spec, but I knew something wasn't right.

    Then I got em to index properly. Now the endplay on both input and output are exactly the same as when I first started.
    Talked to a tranny guy at a local shop and he said the same thing as you that things probally weren't lined up completly. And he said the specs should be the same before and after you add new clutches.

    The spec IN BOTH OF MY TH-400 MANUALS say for endplay on both input and output shafts after rebuild are .007" to .019".
    My output shaft is currently about .015, and the front endplay about .050". This is the same measurements as before I started the rebuild so I'm right back where i started which is a good thing!

    This guy at the tranny shop said that the rear endplay should be about .050" or more. at least .040"! I don't know what to think. The endpalay was .015" before I started and now it is still .015". I asked him what about the spec in the rebuild book (.007"-.019") and he said thats too tight, and oil won't get to the back part!?

    All I know is I am going to stick to what TWO manuals both say. .007"-.019" endplay on both shafts. The rear is good, now I'm gonna have to find another thrust washer to shim the front input shaft endplay from .050" to at least .025" or less. I'd rather have things a little tight than sloppy.

    Thanks for the help!

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

    bouncytruck 1/2 ton status

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    Thanks for the detailed discription of your tranny rebuild. I was considering buying a new tranny but after everything I have read on the site about rebuilding, I'm going to rebuild too. Someone had photos of their TH400 rebuild posted. I'll have to kick my wife's car out of the garage so I can spread the parts out on the floor.

    One quick question, how are you guys getting the tranny and t-case out. Do you own or did you rent a transmission jack? I was looking at an adapter in JC Whittney that goes onto a standard floor jack for $49.

    Thanks again for the info!


    '69 K-5/350/TH350/35's & 6" Lift
     
  10. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Well in my case, the TH-400 was out of my '67 Camaro. It burned up two weekends ago, and I decided I'll learn how to rebuild on the 400 and then I'll dig into my TH-350 and NP205 in my '72 K/5 later this year.

    The rebuild was pretty well straight foreward. The only pain was finding a tranny shop that weren't dicks and actually knew what thrust washer I was talking about on the back of the oil pump to affect front endplay.

    I got the tranny back in and all buttoned up last night, and took it to work today. When I first started it up it smoked a little out of the tranny dipstick. Scared the [censored] outta me and I thought something was wrong and I'd have to take it back out and all apart again to find out what i did wrong. Fortunatly, I let it cool down, added a quart and started it up again, and It was good.
    Drove around the block a couple times and the 1-2 shift was a little slushy. Today I drove it to work and the 1-2 shift got better (harder and crisper) now that it's getting broken in.
    1st and 3rd gear grab even harder than before!

    However... I have NO engine braking (deceleration) in second gear. [​IMG]
    I'll downshift from 3-2 and nothing will happen except for that It'll wind up the engine and then catch 2nd at the appropriate RPM's. I'll have to figure out what exactly is going on, but I think I didn't get something right with the front servo or band. Thats what could cause it. Hmmm. At least I think I can fix it without having to take the transmission back out again.
    Don't mean to discourage ya, but It's fun to do it yourself...It's a learning process.

    And by the way, thanks... Those pictures of the <a target="_blank" href=http://communities.msn.com/Ryans1972Blazer/th400transmissionrebuild.msnw>TH-400 REBUILD</a> were mine. Check em out. I'll do a write up and start a new thread after i'm all done. and I have a few more pictures to post. I figured I'd take pictures so I could show everyone just what is involved... Just as I wished other people would have done so I could have seen... but with a little helpful encouragement from ed rex, I decided to dive into it.


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

    ed rex Registered Member

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    Hey Bouncy, I was fortunate enough to borrow a tranny jack from some dude here at work. It was one of those mechanical scissors type units with the strap to hold the payload. Worked like downtown! Driven by a 1/2" ratchet drive, I simply used my air compressor's 1/2" impact driver to raise or lower. Fine adjustments during the initial removal and the install were made with a 1/2" ratchet driver to afford maximum control. These units sell for about $69 from the HarborFreight Tools site or like $129 from JC Witney. In years past, I rented a tranny jack to remove a tranny but it was cumbersome to use and then you're under a time constraint. I would recommend purchasing one of these mechanical scissirs types with the money saved by doing it yourself! Another good point is that while it's stout enough to remove both tranny and xfer case at the same time without breaking a sweat, it lowers down into a compact little item that stows anywhere.

    Ryan, sorry to hear that there was a slight 'hitch in the giddalong'. Must be a TH400 issue.....:) The TH350, in tandem with the B&amp;M step by steps was really waaaay easier than I had anticipated and left almost nothing to interpretation. My only gripe was with the early shift points (I assume) established by the 'heavy duty' mods to the valve body. That was successfully addressed with the adjustable governor from Summit. After tinkering for a couple of hours, I was able to get it exactly where I wanted. Worked really well.

    I have to give credit where due.....it was JT's encouragement that initially convinced me to do the rebuild myself.
     
  12. bouncytruck

    bouncytruck 1/2 ton status

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    ed rex, thanks for the info on the tranny jack. I have a harbor freight tools catalog right here and I see that the scissor jack has just been marked down to $59. I might have to make the investment.


    '69 K-5/350/TH350/35's & 6" Lift
     

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