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New thread on Yellowbullet about TH400 switch pitch
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Thread: New thread on Yellowbullet about TH400 switch pitch

  1. #1
    Thank you from BT Jedi gear head
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    New thread on Yellowbullet about TH400 switch pitch

    Well been driving the Jeep now for 4 years road/off road, hill climbs and I'm finding that more and more I'm missing the gear ratio in the CJ7 that the Grand Cherokee SRT8 has on the highway. 3 speed verses 5 controlled electronically really seems "too Old School" now having a 0-60 MPH time of 3.5 seconds and a top speed of 175 MPH on the SRT8 really makes the CJ doggy by comparison,
    I've been thinking and doing some research about options..

    1. A gear vendors type of overdrive would be the end all... however it won't work with the Quadra Trac or any transfer case so thats out.

    2. Stepping up to a 4L80 GM transmission is an option but not "Period Correct" for my Mid 1970's build. It may be an option someday...

    3. Started looking at "New" options of a retrofitted lock up converter for the Turbo Hydro 400 transmission supposedly being released in the future but real expensive and I don't really want to be the Guinea pig on the prototypes.

    4. Go full balls out with a GM 6L80 and maybe a full Hummer 242 full time transfer case .....maybe someday...

    5. Resurrect the old 1965-1967 GM TH400 switch pitch transmission...

    Yep I'm picking number 5 for now, I created a build thread on Yellowbullet to try to gather some info that has been lost over the years..

    http://www.yellowbullet.com/forum/sh...d.php?t=594064

    Several companies during the 1970's thru late 1980's offered a switch pitch modification, Kenne Bell, ATI, Rossi transmissions but alas due to cost and somewhat lukewarm interest all the above companies stopped their offerings in kit form.
    A couple custom shops will do the swap but throw in shipping a full TH400 across the country along with cost plus quotes... the cost of this mod starts looking way to expensive for the average guy.

    So if you've got any experience or comments post them here or there..

    I like the ability of having two different stall speeds, the low stall I have now is great now for cruise my only other problem is I run out of gear at 135 MPH.. wish I had more..... a overdrive transmission would get me more but.......

    So for now I'll try this modification.... it seems economical for now.

    1979 Jeep CJ-7 401 AMC, GMC 6-71 Blower 10% overdrive, Bugcatcher with electronic fuel injection and a little N2O for fun, all self built. (this supercharger stuff is easy)

  2. #2
    Thank you from BT ULTIMUS MAXIMUS STATUS tufcj's Avatar
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    Don't know what kind of HP they'll stand up to, but I'm around 425 in my AMX. I'm going to try a swap to a AW4 this winter. Got an AW4 out of a 2001 2WD Grand Cherokee (4.0 L). I've seen a couple of write ups that they're holding up well behind moderately built 360s, I may be the 1st behind a 390. If it doesn't work, I'll go to a 727 and re-gear.

    Bob
    tufcj
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    1967 Rambler Rogue

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  3. #3
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    Quote Originally Posted by tufcj View Post
    Don't know what kind of HP they'll stand up to, but I'm around 425 in my AMX. I'm going to try a swap to a AW4 this winter. Got an AW4 out of a 2001 2WD Grand Cherokee (4.0 L). I've seen a couple of write ups that they're holding up well behind moderately built 360s, I may be the 1st behind a 390. If it doesn't work, I'll go to a 727 and re-gear.

    Bob
    tufcj
    Well some of the stuff I've read said pretty much about the same torque input can be inputted into the switch pitch TH400...the internals of the s/p TH400 are the same as the non s/p version .. it's just the torque converter has moveable vanes to change the stall speed, not as good a loose converter with 3000 RPM stall with full lock up like a 4L80 and the new electronic controlled transmissions like the Mercedes designed 722.6 offshoot i have in the SRT ..but better than just a TH400 one RPM stall limit either favoring either dead stop performance or highway cruise but not both at the same time.

    The Ron Sessions TH400 transmission book describes the amount of engineering that GM did during the TH400 development all the way from moving the 2 and 3 ton Big Cadillac's, Oldsmobile's, Buick's and Rolls Royce's right thru the medium duty rated GMC trucks, buses and big motor homes.
    The only real difference in the OEM car TH400 and the real OEM TH400 heavy duty GM stuff is 16 element sprag clutches verses 8 element roller clutches and straight cut planetary gears verses helical cut.. all of which is a literal slide in upgrade in any TH400, just send the credit card number and install.... no further work is necessary. The cases need no upgrade and the only differences are the bell housings and tail shaft options.

    Now other upgrades are nice... like a billet forward drum to keep everything in the transmission if the stock Cast Iron drum decides to grenade during extreme abuse, or a 4130 input shaft if you have 2000 HP to keep the splines straight, but given that the aftermarket is pretty much mature at this point there really are no surprises that can't be upgraded.
    .
    If anyone cares to understand the lineage and design history of the General Motors 4L80, most parts are interchangeable between the TH400 and the 4L80.
    It's just the 4L80 was designed to replace the TH400 in the 1980's to meet new fuel economy standards and one of the first ways GM chose to do that was by adding overdrive internally to the TH400.

    Another bit of useless information is that the TH400 was also known technically as a 3L80 in the GM world.

    Now the 727 is another good choice for a old school unit too. The newer smaller Jeep stuff from the 1980's and 90's I'm not familar with.
    Last edited by Blown7; 08-18-2013 at 03:32 AM.
    1979 Jeep CJ-7 401 AMC, GMC 6-71 Blower 10% overdrive, Bugcatcher with electronic fuel injection and a little N2O for fun, all self built. (this supercharger stuff is easy)

  4. #4
    Thank you from BT Jedi gear head
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    On another note I'm now reading some of the full out drag guys are running the "new" 2 speed TH400's .. I guess it has all the speed of the 2 speed Power glides shifting but with the torque capacity of the full on TH400.

    http://www.bteracing.com/BTE-TH400-G...l#.UhD43n9GSho

    Then we have all the hoopla about the new Reid TH400 cases that are making alot of people take notice

    http://www.reidracing.biz/transmissi...cases/sh400off
    Last edited by Blown7; 08-18-2013 at 03:38 AM.
    1979 Jeep CJ-7 401 AMC, GMC 6-71 Blower 10% overdrive, Bugcatcher with electronic fuel injection and a little N2O for fun, all self built. (this supercharger stuff is easy)

  5. #5
    Thank you from BT Jedi gear head
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    And the build up on Pirate for Jason

    http://www.pirate4x4.com/forum/gener...smissions.html

    I'm thinking that the Old is New again and that people really want a bulletproof transmission that is simple.
    1979 Jeep CJ-7 401 AMC, GMC 6-71 Blower 10% overdrive, Bugcatcher with electronic fuel injection and a little N2O for fun, all self built. (this supercharger stuff is easy)

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