Beefing up my TH-350

Discussion in 'Competition Camaros' started by Turbo T/A, Jan 29, 2003.

  1. Turbo T/A

    Turbo T/A Veteran Member Lifetime Gold Member

    Well it's almost that time & my bone stock th-350 cant last too long with the new combo & the bottle.

    I am turning to you guys to find out what needs to be done to make a reliable th-350. I already have a reverse manual valvebody & a big fat aluminum cooler mounted behind the front grill.

    Keep in mind i dont need a killer th-350 with transbrake or anything. I just want to upgrade so it will last. Oh & I need it cheap too lol! Just kidding, but lets try and keep me from shattering the wallet. This buildup was expensive enough!

    Thanks in advance

    ------------------
    '81 Viper Blue Z-28
    383 Stroker
    AFR210cc
    Comp XR288HR
    Victor Jr
    750 Holley
    4:10 Rear End
    TH-350 10" 3500 stall

    N.O.S. Cheater 150-250 :D

    New Web Site With Pics & Buildup!
     
  2. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

    8,856
    0
    Dec 8, 2000
    Republic of Texas
    I'd say get rid of that reverse manual VB first.
    Then add some good clutches (Borg Warner for mild app, reds for street/ strip), a new roller sprag and hardened race.
    Set up the clutches with ~.040 on the direct and use a waved plate, forward with .020-.025 and no waved, intermediate with a waved.
    Possibly add a clutch to the intermediate and direct.
    Use 4L60-E low/reverse steels.
    Be sure all the bushings are good, replace pump, rear, stator, direct drum bushings anyways.
    Use a TransGo Stage 3 shift kit, adjustable modulator.
    A new red lined band.
    Be sure pump gears are in good shape and not too deep in pump.
     
  3. BlownBigBlock

    BlownBigBlock Veteran Member Lifetime Gold Member

    3,884
    0
    Mar 2, 2000
    Carlisle PA
    Your going to need an intermediate sprag unit. Your looking at about $300 for one.

    When I was building mine, I talked to 4 tranny companies... TCI, B&M, Coan, and ATI.
    They all said the same thing, the weak link of the TH350 is the intermediate sprag assembly.
     
  4. Lowend

    Lowend Administrator Staff Member Lifetime Gold Member

    13,687
    86
    Mar 25, 1999
    San Jose, CA, USA
  5. Turbo T/A

    Turbo T/A Veteran Member Lifetime Gold Member

    Well here's the word of the day. After talking to many builders in my area, its come to this.

    A TH-350 is going to be more expensive to build than a th-400...

    Now with this said, what kind of modification do i have to do to fit my car with a 400. My builder actually does transmissions as well including the manufacturing of his own valvebodies ect.... It's going to come with all the trimmings & a reverse manual valvebody.

    I think the yoke has to be changed...how bout the driveshaft? Will the headers fit the same? Starter? Flywheel?

    Sorry I've always been around th-350's & dont know much about anything else.

    ------------------
    '81 Viper Blue Z-28
    383 Stroker
    AFR210cc
    Comp XR288HR
    Victor Jr
    750 Holley
    4:10 Rear End
    TH-350 10" 3500 stall

    N.O.S. Cheater 150-250 :D

    New Web Site With Pics & Buildup!
     
  6. EdgarR

    EdgarR Veteran Member

    324
    0
    Jun 27, 2002
    aurora, il us
    I have always found that it is more $ to beef up a 350 than just buying a 400 or not that much more. But keep in mind that the 400 does rob a little more power than the 350 but for street/strip not enough to make or break you. You do have to change the yoke, drive shaft and cross member. I know there is a way of using the 350 cross member but not sure how.
     
  7. Turbo T/A

    Turbo T/A Veteran Member Lifetime Gold Member

    More info on this would be greatly appreciated.

    I did have a 700R4 in my car for a while last yr & i had to move the crossmember back a bit. Will the TH-400 bolt up to these locations or will i need to make even more holes?

    HMM i thought the two driveshafts were the same length but with different yokes?
     
  8. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

    8,856
    0
    Dec 8, 2000
    Republic of Texas
    Stroked,
    OK,
    First of all you don't HAVE to have the aftermarket sprag IF you use a VB kit that gives PROPER shift timing. Most aftermarket kits and manual VB's don't take this into consideration and cause the sprag to take a big hit because the clutch locks first, then the sprag and it isn't designed to take that kinda hit. Even the heavy duty, high dollar, high capacity element type sprags will break if your shift timing is wrong. it will take longer but it is still going to happen.
    EVEN on a TH400. Believe me. I broke one.
    The Th400 stock intermediate roller clutch is not much beefier than a Th350, the old style 16 element sprag type clutch isn't much better either. I broke one of these recently because I was being hard headed and on a budget.
    SO that said you can get away fine with using the Th350 if you use the right VB kit. That PROBABLY means you need to get rid of the manual VB BUT if it uses the modulator and doesn't totally bypass the 1-2 accumulator it may be OK.
    Next the TH400 IS beefier and is my trans of preference becuase I've built them up to hold 1500 hp and it really doesn't take much other than stock stuff with some HD clutches and bands.
    SOMETIMES you can use the same driveshaft with a different yoke. I have done it in a '71 Camaro.
    The best way to do the crossmember is to cut the mount off the frount and weld it to the back of the crossmember, usually also have to slightly drop it to retain proper driveline angles.
    This keeps it in the stock holes.
    There is 6 3/8" difference in the mounting pad location of a short shaft 350 vs 400.
    All the other harware is the same, except maybe the dipstick and dust cover. Modulator line needs to be rebent or modded.
    TH350 and 400's can use the same converter.
    Last,
    Not sure where you are at but I have a Th400 with all the bada$$ parts I'll build to your specs if you want. I don't need it as I will soon be pulling my TH400 out and replacing with an overdrive.
    So will already have a spare.
    It is complete with HD sprag, TransGo VB kit for whatever setup you want, full manual, manual/auto, race, street, whatever.
    It would be $550 exchange or $650 outright. I would build it and meet you somewhere if within a reasonable driving distance. 200 miles or so.
    It has a deep pan, red clutches, HD band, HD sprag, all clearances blueprinted, all new seals, etc.. Ready to go. 800hp no problem.
    email me at jakeshoe@hotmail.com if you need more info or are interested. I'm in north TX.
    Also I can modify your crossmember if you bring it to me.
    Anyway , enough of the sales pitch.
    The TH350 is a good trans and just depends on what you plan to do in the future.
    I'm building a Th350 for Old School this weekend for his 10-second 2nd Gen.
     
  9. craggar

    craggar Veteran Member

    5,769
    0
    Jul 28, 1999
    edmonton
    If you want to go TH400 you really don't need to do much to it, as little as a shift kit.It should be plenty strong enough as long as everything is in good shape.
    I haven't done the swap but know that the d/s needs to be shortened,the tranny yoke is different and you can turn your TH350 crossmember around and should be able to reuse 2 of the original holes then drill 2 more.Somebody else on here had to drill all 4 but my friend reused 2.Maybe 2 maybe 4.
    IMO the TH400 is more than adequate in stock form for most street cars and alot of race cars.They do weigh more and take more power run which is why some of us run the th350 instead, but if I don't get mine to stop breaking this year I'll be using a th400 soon. [​IMG]
     
  10. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

    8,856
    0
    Dec 8, 2000
    Republic of Texas
    craggar,
    Just out of curiousity, what is breaking in your trans?
    What valve body/kit are you using?
     

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