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Author Topic: Turbohydromatic 70R4 vs. 700R4 tranny  (Read 7591 times)

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AAMD80ORD

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Turbohydromatic 70R4 vs. 700R4 tranny
« on: August 10, 2007, 08:35:59 AM »
What is the difference between a Turbohydromatic 70R4 vs. a 700R4 transmission? 

Chuck

Todd Stahr

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Re: Turbohydromatic 70R4 vs. 700R4 tranny
« Reply #1 on: August 19, 2007, 01:16:03 PM »
Have never heard of a 70R4, Turbohydramatic is GM's name for the automatic transmissions in general. Usually just shortened to THM or TH, like TH400, TH350, TH700R4, TH2004R, etc. The later cars have a different designation, as in 4L60, 4L60E, which are both derivatives of the 700R4, with the E denoting electronic controls. To break down the new system, 4 is how many gears forward it has, L is longitudinal or not a transverse setup like a front driver and the 60 or 80 is code for how much torque capacity the trans has.

There are minor differences between the 700R4 and the 4L60, most internal parts will interchange like a good number of seals, friction and steels, bands etc. The front pumps will bolt in as they use the same housing, and the early pumps had 6 vanes, later pumps were 10 or 13 vanes. You can upgrade to the later 13 vane pump if you have a 6 or 10 now. The main difference with the 4L60E is simply the valve body, it does not have the TV (throttle valve) cable like the earlier 4 speed autos do, its line pressure, shift points and other operations are controlled by the ECM that also monitors the engine. There are other differences, but for the most part its the valve body that is the big change.

The 4L60E that came with LS1 cars has a separate bell housing, whereas the 700, 4L60, 400/350 and all the way back to the Powerglide and Super Turbine 300 2 speed that came in our 60s Pontiacs had an integral bell housing, it was part of the case. The reason for that is ease in assembly and only one trans part number for different applications and engines, the bell housing is much cheaper to make than an entirely different transmission case.

A short shaft 350, short shaft 400, and the 2004R are all the same length, needing a different yoke for the 400 trans. So other than the TV cable, yoke, and the crossmember move, the 2004R is a direct replacement for the 400. it wont take the abuse a 400 will, but they stand up to sensible driving pretty well. You get the bonus of overdrive and a lock up converter, provided you connect the lock up feature. If you dont work that out, the trans wont live more than a couple thousand miles at best. The TV cable being misadjusted will make your trans junk in a matter of minutes.

700R4/4L60 use a chevy bolt pattern for the bell housing, they wont bolt to a traditional Pontiac, like the 455 or 428 without an adapter. They will work well for an OD in any classic Pontiac though, with the same attention paid to TV and converter lock up as the 2004R, and the addition of the adapter plate. If you have a 3rd gen then you probably have a chevy engine, and a 700 is a bolt in swap for the cars that didnt have the OD originally.
Performance and general repair tech. Traditional Pontiac V8 is my specialty, as well as automatic transmission repair/diagonossis. 2nd gen speciality, and with the addition of the 98 Formula 4th gen LS1 I am getting to know them real well. Holley and Qjet advice as well.

Chalk mark restoration and date codes arent my thing. W.O.T. is my thing..

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Re: Turbohydromatic 70R4 vs. 700R4 tranny
« Reply #1 on: August 19, 2007, 01:16:03 PM »


 

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