So, I got around to fixing my speedo driive some time back. Got the correct gear with matching drive. The OEM gear had popped off before I got the transmission. New speedo head. Speedo operated fine and correctly for a little while. Then the needle started pulsing. Then no speedo. Figured the drive gear popped off again. It did. I put the gear back on but this time, left the cable disconnected. Oh, I had put a new cable in some time ago. Chassis Engineering trans cross member. My own bracketry to use the '86 'Vette trans. I have a VSS driven directly off the trans. See pic. That put the cable end and housing in to the cross member a bit. I figured that and the curve to head up front created enough of a bind to make the drive gear pop off. My current fix. I'm waiting for a 90* drive that I'll put on the VSS, then the cable to give the cable a more direct route and, hopefully, take all bottom end bind out. Thoughts?
Looks good to me- - - -cable routing is something some people don't consider, and it can create problems. The cable-drive tachometers we used to use on Mallory dual point distributors had a bad habit of lagging in response time just enough to let the engine run past redline if we weren't very careful about the radius of the loop the cable made from the engine compartment to the dash. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
You may not be interested but we have gone to gps speedometers on nearly all the rods we build and some of the restorations. No cables, gears, or ratios to worry about and you can switch to any tires or or rear gear and they stay dead accurate. They are starting to make some that fit the factory instrument cluster on popular models. There are virtually no "dead spots" for gps units anymore. Just a potential option to consider.
There are virtually no "dead spots" for gps units anymore.
I wondered about this when I went through the Chesapeake Bay Bridge-Tunnel twice this week?
[I was using Apple Maps routing - Verizon Cellular - there was no lost signal.] [I’ll also use a GPS next time - to see if the two devices behave the same.]
Last edited by tclederman; 05/17/20196:37 PM. Reason: Added bracket comments.
MNSmith: back in the early days of the 700R4, like thru 87, the output shaft of that trans had two holes drilled in it to locate the retaining clip for the speedo drive gear. Corvette was the only odd-ball, having a specific extension housing which used the rearward locating hole, meaning the positioning of the driven gear in the extension housing was different also. You said Corvette 1986, but does it really have a Corvette extension housing? Does the output shaft have one or two holes drilled back there for the drive gear? Was the output shaft maybe changed out for one with a single hole? You can mix and match a lot of parts in that tranny, but it doesn’t always work out. Sounds like the drive and driven gear aren’t lined up correctly. Just a few things to consider. Good luck, Dave
I have the Dakota VHX gauges with GPS, cruise, 1/8 and 1/4 mile time. also 0-60 time. It has odometer. The cruise is just the turn signal handle that fits my 57 turn signal switch. I have a Frankland quick change rear end with about 124 gear ratios available from about 212 to 840 so I didn't want to have to mess with calibrating. The speedo also has memory in case you lose signal.
MNSmith: back in the early days of the 700R4, like thru 87, the output shaft of that trans had two holes drilled in it to locate the retaining clip for the speedo drive gear. Corvette was the only odd-ball, having a specific extension housing which used the rearward locating hole, meaning the positioning of the driven gear in the extension housing was different also. You said Corvette 1986, but does it really have a Corvette extension housing? Does the output shaft have one or two holes drilled back there for the drive gear? Was the output shaft maybe changed out for one with a single hole? You can mix and match a lot of parts in that tranny, but it doesn’t always work out. Sounds like the drive and driven gear aren’t lined up correctly. Just a few things to consider. Good luck, Dave
Thanks Dave! My output shaft has two holes. I believe I put the clip in the forward hole.
Better shots of my tail shaft housing. I might have done some mixing and matching? It's been a while.
