TH400 Rebuild - Help me put together a list?

Discussion in 'Transmission & Driveline Topics' started by evilWS6, Jan 20, 2018.

  1. Fbird

    Fbird Veteran Member Lifetime Gold Member

    Feb 12, 2011
    atlanta, ga
    yup Jakes tips n tricks pics are all gone :(
  2. camaro71/holland

    camaro71/holland Veteran Member

    Aug 27, 2003
    The Netherlands
    Good/quality kits come with all bushings included. And if you have a transmission shop around, you can always get a new bushing if you srew it up....;)

    Don't need to replace the whole pump, unless after inspection it turns out that it's warped/damaged badly. Check the straightnes on both halves, measure the play between the drive/driven gear and the pump face > replace gears if too much play, replace the bushing and the seal, finish your beer. There are some other minor checks covered in the manuals.

    Speaking of which........knowing that 'the winter was coming' one time, I haved saved a couple technical topics on my hard drive. If your interested, you can 'borrow' my ATSG manual for the 400, over 100 pages pdf from the book I was referring to (CK Performance) that he published on the net and a powerpoint presentation of 99 slides with a lot of tricks and upgrades for the 400 alone (including pics and information by Jakeshoe from here).
    evilWS6 likes this.
  3. accelo

    accelo New Member

    Jan 12, 2015
    The tools used to get the lip on the rubber seals has not been mentioned. Their are a couple of them and everyone has their preferences. One is a piece of tubing with a loop of wire on the end. Piano wire is bent into a "U" shape about 3/4 long and the ends inserted into a piece of tubing. Then the tubing is smashed down enough to retain the loop of wire. You go around the edges of the piston with this loop of wire till you can get the lip to lay down enough to get the piston in. Sometimes rotating the piston while preforming this task. It is something that one has to learn. A second tool is a small and very thing plastic circle. Some kits even include them. This is the tool I would give a beginner. The outside edge is inserted between the piston and the clutch and rotated around. Less likely to damage the seal. Air check the clutch pack after assembly, this will confirm the seal is damaged. They all leak a little when tested with air. A feel for the amount is something you have to learn and I cant explain well enough in writing. ]
    Best of luck on your project.
  4. craig1980

    craig1980 New Member

    Dec 27, 2009
    new hampshire
    Hi just wanted to add my two cents, I'm actually a transmission Builder I would recommend contacting Transtar Industries or another major supplier like that for your parts they also sell a nice atsg manual for that unit that is very helpful.
    If you have questions while you're building it you're welcome to contact me. Craig
    evilWS6 likes this.
  5. Da_Raabi

    Da_Raabi Veteran Member

    Jan 19, 2011
    Daytona Beach, FL
    This was a post I put together on a C/K truck forum I'm on. I did a TH400 complete rebuild early last December and have been driving it daily ever since. No problems thus far. I found it to be a very easy rebuild. Complete thread here:

    Below is a quote from one of my last posts in the thread:

    I'm glad you found the thread useful. I would not hesitate to use TPUSA again, however I feel that this kit is a better deal as it includes a lot more parts for roughly the same price:

    Also, I used the ATSG rebuild manual for my rebuild, supplemented by the B&M rebuild manual (for some of the more "at home" operations where you do not have the "correct" tools) and an extra page or two I found online. All three manuals were readily available in PDF form with a simple Google, here are links:

    ATSG TH400 Rebuild Manual PDF:

    B&M Transkit Rebuild Manual (use only for reference. It is highly recommended you DO NOT use the modifications found in this manual. Only use it for additional reference)

    Attached to this post are two additional PDF files. **NastyZ28 would not allow me to upload pdf files - google may help** The first is a simple exploded diagram, the second is a recommended rear band/reverse servo inspection and setup write-up I found. The ATSG manual does not go into any detail on this subject so I found it helpful.

    Additional Notes:

    • Watch for the "fretting ring" or "case saver ring" behind the center support. It is important that you use one of these if it is present. The ATSG manual does not reference it during tear-down, but does explain it during rebuild.
    • Inspect your plastic "silencer ring" for damage. It goes between gear sets. Mine was all chewed up, so I had to get a new one. $10 on ebay. I have an extra if anyone needs it too.
    • ABSOLUTELY use a Transgo TH400 1&2 shift improver kit. Summit had the best price I could find on it. I used all parts except the manual-low override valves. The spring/hole size I used is in a previous post. This setup resulted in a not-too-firm shift that I like a lot. Summit had the best price by far:
    • Take extra care to measure and inspect your governor and it's bore. This is something I did not do and am now paying the price for.
    • Folks seem to complain about getting the center support bolt out (the one behind the valvebody in the case). A 1/4 drive 12-point socket fits very nicely and makes removal and installation simple.
    • Be sure to blow/clean out the existing cooler lines and in-radiator cooler. I added the Hayden after the existing cooler so that I am using both.
    • Definitely get a new torque converter. Stock replacements are cheap on RockAuto.

    If you have never rebuilt an auto trans before, the TH400 is a good one to start with. It's really a pretty simple trans. Just take your time, lay out your parts on a table in the order of removal, and stay organized. DO NOT RUSH. The extra time I had due to parts problems allowed me to really study the manuals and do lots of online research about what needs to be done and when. READ READ READ. You should know the manuals front to back before you get started. Always read ahead to make sure you know whats coming.

    STAY CLEAN. I bagged all assemblies after they were completed in clean,new garbage bags.

    I used two Home Depot 5 gallon buckets with a gallon of low-odor mineral spirits in each for cleaning and rinsing. Clean in the first, rinse in the second.

    I chose to soak the bands and the clutch frictions in tranny fluid over night before installation. Some say this is not necessary, but I figured why not? Its free and I had lots of time.

    I only needed assembly lube once to hold the thrust washer to the back of the direct drum during installation. I just used vaseline (from the babies. It smelled like flowers lol). I would not waste your money on actual assembly lube, I never needed it. Tranny fluid had enough "stick" to keep everything else in place.

    I used Walmart Dex/Merc tranny fluid. At $11 per gallon the price was right. It's made by Pennzoil so it should be good stuff.

    Anyway, long post. Hope its helpful for anybody looking to take on this project.

    Oh. A couple of handy vidjayos I found on the you-tubs:

  6. Da_Raabi

    Da_Raabi Veteran Member

    Jan 19, 2011
    Daytona Beach, FL
    Not if you know how to use the wayback machine... ;)

    I used it to get the original tips and tricks page. Saved it as a PDF... I'd upload it here by I can't upload PDF files.
  7. evilWS6

    evilWS6 Veteran Member

    Jan 22, 2013
    You guys... absolutely freakin' rule. Thank you for those replies, and a special thank you for that MASSIVE reply - I've saved all those links and PDF's.

    Also, for what it's worth, you can use "WeTransfer" to share files (like PDFs) for free. Just upload a file, copy the link once it's done, and boom - share the link. They let you upload pretty big file sizes, and I don't *think* the link expires, but I could be wrong.

    Once I get going I'm sure I'll be messaging some of you. If anyone else has any more PDFs feel free to PM them over or post them in here for future reference to everyone!
  8. Da_Raabi

    Da_Raabi Veteran Member

    Jan 19, 2011
    Daytona Beach, FL
    I'm glad the post was helpful. Just so you don't have to dig through my other thread, here is how I set up my shift kit:

    I chose not to go with the shift kit's manual low override mod. I know it can be handy in extreme situations, I just don't want to accidentally slide into first at 45mph and blow the engine sky-high. I figure if I need it I can always do it later.

    Also went with a slightly more aggressive 1-2 shift setup. I used the orange/red spring combo. I don't want to be chirping the tires every shift. In a dually that's probably not good!

    I'm going to do the separator plate mod this evening. I'm using the TransGo plate, and plan to drill:

    2nd Feed: .093 or maybe a bit more. This is Range 2 for trucks

    3rd Feed: Stock, again Range 2

    3rd Accm: Stock, again Range 2

    Also, if your trans used a plastic accumulator piston - REPLACE IT. They make an aluminum one for like $10 or less. When I opened up my trans the first thing I noticed was that the plastic piston was broken. Installed an aluminum one and now good to go forever!

    You can see it sitting in the bottom of the pan here.

    extra parts.jpg
  9. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

    Dec 8, 2000
    Republic of Texas
    Quite a bit of my old info is on the Crankshaft Coalition site. Look there for rebuild tips.
    Alto Reds are my least favorite clutch material. Stock is better IMO. Kolene steels are a waste of money.
    I sell rebuild kits at
    Turbo70Camaro likes this.

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