Speedo / Tach / Gauges: 700R Speedo Cable For OEM Stude Speedo

[JoeHall]

The speedo stopped working in less than 100 miles, in the GT with the recent 700R install. When I disconnected the cable at the tranny to see why it had stopped turning, I discovered the square end of the cable fit very sloppily in the square hole in the end of the plastic pinion. I figured it had somehow wallowed out, so ordered another pinion. When it arrived I compared the new pinion's square hole to the end of the cable, and to the end of a spare Stude cable. Turns out the end of the Stude cable and the one that came with the kit is .104" square, and the hole in the pinion is .150" square. So it appeared there was another learning curve to climb.

I then did some reading on speedo cable core/end sizes, and discovered there are three, and each is used for different applications: The .104" is for passenger cars, light trucks and vans; the .150" is for heavier trucks and vans, and a .187" is for big rigs. I then double checked several 700R pinion catalogs' listings, and found no reference to square hole size, only to number of teeth.

Looking closer at the square hole in the pinion, I discovered it is 1 & 3/8" deep, and the first 1/2" is .150" square; afterward, it quickly tapers to .104" for the remaining 3/4" or so. So, it appears this was GM's way of making the same pinion fit both the .104" & .150" applications.

My problem is, the cable I bought only sinks the tip of the cable about 3/4" into the pinion. Looks like the fix is gonna be to install a universal core, and cut it about 3/4" longer so it will bottom out in the pinion.

Has anyone else ever encountered this ?

Thanks,

[PackardV8]

Yes, Joe, I discovered the same situation when I installed the 700R4 in my Avanti. It's a much easier and less expensive fix than those trannies with only electronic output.

jack vines

[JoeHall]

Jack,
I agree the cable setup is a lot cheaper than the electric setup. This cable fiasco is just one more "notable" about swapping a GM tranny into a Stude. The mod is still worth it to me, but the first one was a learning experience. I would not care to do another one, but if I ever did, it would probably go cheaper and easier.

I went ahead and ordered a LoKar universal cable, that can be cut to length. At $70 it is pricey, but the one that came with the kit (for $30 extra) was way too long, at 84" instead of 69". This way I can get rid of the extra loop in the lower left of the engine bay.
Thanks

[nibbs53]

Check these out.

http://www.bing.com/images/search?q=gps+speedometers+for+street+rods&qpvt=gps+speedometers+for+street+rods&FORM=IGRE

Patrick.

[JoeHall]

Check these out.

http://www.bing.com/images/search?q=gps+speedometers+for+street+rods&qpvt=gps+speedometers+for+street+rods&FORM=IGRE

Patrick.

Patrick,
I had noticed those, but at $370 and up, they were too rich for my blood. I also want to keep this car semi-stock in appearance. I may put an era correct Sun tach on it though, since this GT did not come with a tach.

[wittsend]

I used a cable from a late 70's Mopar truck (on my '64 Daytona). Seems like a lot of cables would have worked, but I just liked the outer sheathing thickness, the connectors and the general appropriate length. I think it was about $6 at U Pick Parts.

Just a word of warning regarding the 700R4 speedometer gears. There were two housings. I can't recall the exact numbers but it was something like 37 teeth and down took one housing and 38 teeth and up took another housing. So, if anyone needs to adjust for correct readings make sure the housing matches the gears