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Speedhut Electric Speedometer!

johntennyson

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I'm feeling pretty chuffed right now as I've been able to make an electric speedo work in my Sprite. When I re-restored it ten years ago, I went to the Rivergate 5-speed conversion which uses a Nissan 210 gearbox. I didn't like the option to use the mechanical conversion for the stock gauge, so I went without a speedometer--or a fuel gauge-- for a long time, which led to episodes like this...


...when I ran it out of gas on the Pacific Grove funky old car tour. After a good experience with an electric speedo in another project car, I ordered a speedometer from Speedhut and their sending unit for GM transmissions. It looked like I might be able to somehow make it work, if not directly in the Nissan trans, then from the end of the speedometer cable. Maybe.

It turned out that the thread spec of the receptacle on the Nissan trans is the same as the GM or Chrysler. Thank you, SAE or whoever!

The only problem is that the rotating core of the GM sender is a 3mm square-section bit and the rotating end of the Nissan cable is ~4mm round with a tab swaged into it to fit into a slot in the receptacle.


Even Palo Alto Speedometer wasn't sure what to do. I wound up making a mandrill to duplicate the core of the GM sender by filing a 3mm nail into a square section and taking a 3/4" long section of 1/4" brass tubing and squeezing it around the mandrill with pliers to get a square section with a tab. It fit both the sender and the trans and engaged the slot in the trans receptacle.



I later made one out of stainless steel and stuck the works in the car. In the picture, the brass one is on the right, the stainless one is installed in the sending unit.

It works! The biggest problem I had was with the gauge mounting ring. The gauge itself is remarkably shallow and is held in place by a large plastic ring which threads onto the gauge body. On my gauge's mounting ring, the threads weren't cut all the way to the end of the ring and it jammed a few mm short of secure and it was a shouting obscenities PITA to get back off. I cleaned up the threads by hand and when they were still really tight, loosened them up enough by running a scouring pad over them. If you use one of their gauges, make sure the mounting ring will screw all the way down cleanly BEFORE sticking it in the dash. Other than that, it works and looks great. The great thing about Speedhut is that all their gauges are custom jobs, with a lot of appearance, size and function options. You can even upload graphics to their site and they'll put them on the gauge, which is how I got the Austin-Healey script on mine. Maybe I should have sent them the "British Leyland Special Tuning" emblem... Hmmmm...



The only problem now is that I have no excuse for running out of gas again!
 
I too John will be running the 210 gearbox and knew that I would be using different ratios differentials at times. I still wanted to have an accurate speed and trip-meter and knew that changing differentials and tire diameters would interfere with its accuracy. So, instead of fooling around with cables and transducers I chose to have Speedhut build a GPS in the likeness of the original with a few exceptions. It’s great to know that the GM sender will adapt if I ever have to go to cable. Great job on the conversion!! Nice looking car too!!


View attachment 28463
 
Excellent solution. I already had an angle adapter from Rivergate, so I just installed my GM sender onto it for my electronic speedo. Next time I have the engine out I may look into eliminating the angle adapter.
 
Max! Those look great! Did you send Speedhut a picture of the original gauges?

Yeah, I guess the GPS unit is probably the ultimate solution, but I just still have a hard time believing they'll work as well as more 'traditional' gauges. I seem to remember Jimmy Vasser testing a race car with the throttle controlled by GPS (!) and it worked well. I guess I just want other folks to try it first!

Trevor: Even though everything seemed to bolt up perfectly when I installed the transmission, when I look in the tunnel at the shifter opening, it looks like the tail of the transmission is closer to the left side of the tunnel, leaving a lot of space on the right side of the transmission where the sending unit screws in. I cut another access port in the area (same size as the original trans oil filler openings) and the sending unit is a close fit, even with the transmission mounted off to the left. I'll take and post a photo in the next week or so.
 
Thanks guys.
 
I had a mechanical speedo on the datsun transmission originally. So when I installed an electronic speedo I just installed the sender onto the angle adapter. It works, so I should probably leave well enough alone.
 
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