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1962 Buick Skylark / 700R4 transmission


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  I have replaced the Dual Path transmission in a 1962 Buick Skylark with a 700R4 from a V6, 1982 Firebird.  The connection between the Dual Path and speedometer was mechanical.   The 700R4 transmission, however, has an electronic output to the '82 speedometer.  I'd appreciate any suggestions on creating an interface between the 700R4 and the mechanical 1962 speedometer. 

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  • 2 weeks later...

It's quite simple.  You remove the tailshaft housing of the trans.  On the output shaft you'll find the "tone wheel" which the speed sensor gets its signal from.  This wheel is held onto the shaft by a clip.  Remove the clip and slide the tone wheel off of the output shaft.  Then install the speedometer drive gear (with the correct number of teeth for the tire size/rear axle ratio on your car AND with the teeth aimed in the correct direction) and you can use the same clip (if you didn't break it).  Then, you'll need the appropriate cable connection plug for the transmission and the gear teeth ratio.  Along with the appropriate cable driven gear.  With it all swapped out, the tailshaft housing back where it came from, attach the cable, and drive the car.  A local trans shop should have the speedo gears and maybe the plug the driven gear slides into, with the appropriate seal.

 

Years ago, we had to do this in order to use a THM700 that was configured for the speed sensor on a vehicle that used the gears, but the older trans was a THM700 so all of the parts were there to do the deal.

 

Enjoy!

NTX5467

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  • 3 weeks later...

FIRST thing is to find a trans case to fit the back of your engine.  Then fabricate cooling lines.  The rear mount interface (and placement thereof), then the swap of the speedometer gears and such.  Ought to "wake things up".

 

Enjoy!

NTX5467

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Posted (edited)

    Replacing the dual-path with a 700R4 is not too difficult.  I used a transmission from a V6 Pontiac Firebird (1982).  It has to be from a smaller engine.  You need an adapter plate purchased from aluminumv8.com (D&D Fabrications).  The fellow there can give you details about which tranny to use.  One thing that I found out is that when regular hex-head bolts are used to attach the upper part of the tranny to the plate, the bolt heads do not clear the firewall.  I used flat-head bolts from Harley-Davidson to get the heads flush with the plate.  These bolts can probably be found elsewhere, too.  You also need to countersink the upper holes in the tranny to accept the tapered flat-heads.

    I had to make a new rear transmission support to replace the original one.  You also need to make a transmission close out plate or purchase one (from D&D).  The D&D plate is fiberglass and needs to insulated because the exhaust pipe runs close to the plate.  I got some adhesive, aluminum-faced insulation from Design Engineering (designengineering.com).  Alternately, the exhaust pipe could be insulated.

     The 700R4 is larger than the dual-path, so you need to enlarge the transmission tunnel.  I basically cut around the current tunnel at the floor and moved the remaining top up high enough to clear the tranny and then filled in the gap with sheet metal.   A downside is that the tunnel gets to be a little large.  There may be another way to make a new tunnel, but this one worked. 

      I also decided to replace the two-piece driveshaft with a single-piece one.  Because the rear of the transmission is now higher, I had to cut out the floor along the driveshaft and make a new section of floor to clear the driveshaft.  This change in the floor is not too noticeable.

      The transmission that I used has an electronic output for the speedometer, which doesn't work with the original speedo.  Some suggestions for resolving this problem are in the responses to my original question.  There may be a 700R4 with a mechanical output that could be used, but I don't know.  The fellow at D&D may have a suggestion.  

Edited by Blue_Sky_62 (see edit history)
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    Another change to make is the addition of a transmission fluid cooler, since the dual-path is air-cooled.  I got a plate-type one from B&E (?) and mounted it to the two pieces of cross-bracing in front of the radiator.  It works very well.  You need to run lines from the tranny to the cooler.

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