so how do i make my speedometer work?

[chromedRAT]

just a pre-emptive question, although i hope to be at this point in my project very soon. i took out the old hydromatic and straight 8 in my 50 pontiac in favor of a 327/TH350 combo. how does everybody go about hooking up a working speedometer? do i just splice my speedo and the tranny together, and just figure out how much off it is and mentally correct to follow the right speed, or what? often wondered about this, any ideas, fellas?

[Pist-n-Broke]

Most major town have spedo repair shops. Making cables is a common part of there job. They can put any end on you need. There is a gear drive adapter that goes on at the tranny end to correct it at 50 or 55 mph. The other thing they can do is change the magnatasim in the head if necessary. I use a place called I.S.S. or Insterment sales and service in Portland Oregon, it's the closest one to me. Prices will very but about $50.00
The Wizzard

[MercMan1951]

Yeah, speaking of which, how do I make a 1951 Merc speedo work with a 1987 Town car trans/speedo cable? I really hate to cut up the Merc dash...there is a speedo shop called Specmo on Woodward not too far from me, they do recalibrations and such, but the physical mounting of the new cable to the old speedo isn't anywhere near the way they did it back in '51...anybody have ideas? By the way, I DON'T have to original speedo cable anymore, either. http://www.jalopyjournal.com/ubbthreads/images/graemlins/crazy.gif

[Crosley]

speed-O cable works well to hook the tranny to the speed-O.

then calibrate with speed-O gears inside the trannny

[Deuce Roadster]

Once you get the speedometer hooked up.....

You can correct it by using the info from this site....

http://www.tciauto.com/tech_info/speedo_gears.htm

BTW....... Many older Fords speedometer cables hook directly to the Turbo 350, Turbo 400 and PGs. 1940 Fords will, so will 56 F100s. Then just adjust the driver/driven gears inside.

.

[Smokin Joe]

The TH350 has 2 gears for the speedo. One on the end of the cable that meshes with another in the tailshaft. Drive the car between mile markers on the freeway with the speedo reading exactly 60mph. Record exactly how many seconds it takes. It should take 60 seconds. Do this untill you're sure you have a good reading. Don't use mile markers that are near an on ramp, they may have been moved because of the ramp. Compare your reading to 60 seconds to figure out the percentage you are off. The gears are color coded and if the tranny shop knows what gears you're using and the percentage off they can get you the correct gears to make it read right. Any tranny shop should have a chart. You may have to replace one or both gears. You can do this at 75mph too, but I forget what the exact time is. It's something like 48 seconds. If you have a speedo check area on the freeway near you, go read the sign to get the right time. Mine is now 10% off in the Chevelle, so if the speedo says 70 I'm actually doing 77. At 30 I'm doing 33. As you can see, the faster you go, the farther off it is. That was the closest set of gears the shop had on hand when I did this. I'm not going to fix it till I swap the rear end. When I first got the Chevelle it was passing people on the freeway at an indicated 50mph on the speedo. I pegged the speedo at over 120 once when it was reading that way! God only knows how fast I was really going, but if you figure 50 on the speedo was actually 80mph and do the math for it reading 120, I think you could say the damned thing hauls ass! It's supposedly got 2.73 gears in it now, but I have the origional 3.31 12bolt to put in it when I get around to it. Still had some pedal left too, but I figured pegging it was fast enough. Wish I could have run the black line on the salt back in August to see what it would really do. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[MercMan1951]

I know about under driven speedos and such, and you guys have hit the nail on the head for most guys who are swapping old stuff to a chevy TH350 or TH400, but for me, the damn cable (from a 1987 Town Car) does not physically connect to the 1951 speedometer. So now what?

[Smokin Joe]

Does United Speedometer Service handle this kind of thing?
I think that's the name. Look for the add in the mags.

[chromedRAT]

god i love this place.

[Flat Ernie]

[ QUOTE ]
Drive the car between mile markers on the freeway with the speedo reading exactly 60mph. Record exactly how many seconds it takes. It should take 60 seconds. Do this untill you're sure you have a good reading. Don't use mile markers that are near an on ramp, they may have been moved because of the ramp.

[/ QUOTE ]

This will get you into the ballpark, but the ones near the ramps aren't the only ones off. I've found quite a bit of variation in freeway mile markers everywhere & unless you're on a known good stretch such as a speedo check area like SJ mentioned, you're probably not going to get perfectin this way.

An alternative method & one I prefer to average them out over a larger distance - at least 10 miles & use the odometer to figure out the percentage difference instead of timing. The pros with this method are it doesn't require you to keep accurate time (the smaller the distance you use, the more accurate the time has to be) nor a perfectly steady speed. The biggest drawback, IMO, is that it requires you to accurately interpret your odometer and it only works well if you have a tenths readout.

One other method I've heard of, but never tried nor confirmed to be true was to get a known good pace car to pace you at, say, 60mph. Check your reading at 60 and write it down. Open your speedo up & locate the needle tension spring. Then get a variable speed reversible drill & spin the cable until you get your speed. Adjust the spring tension until the needle reads 60 and you should be good to go.

Like I said, I just heard about this method from an old-timer and have never verified this to be true or accurate, but thought someone else might be able to shoot holes in it or verify it. It seems to me this might be good for small errors, but maybe not for larger discrepancies. The other thing is, it might only be good for your target speed - I simply don't know.
Anyone?

http://www.jalopyjournal.com/ubbthreads/images/graemlins/cool.gif

[C9]

[ QUOTE ]
Does United Speedometer Service handle this kind of thing?


[/ QUOTE ]

Yes they do.
They made up a speedo cable for my 32.
Nice piece, HD outer etc.

They have a website as well as a catalog.
Nice folks, friendly, easy to deal with, good service.