JillsVette

Hey guys I have been busy trying to figure out what's up with the speedo not working. The car has speed control that I am positive does not work because I cannot turn the input or output. So I'm just going to by pass it for now with a longer cable. Although this is a problem it's not the reason for the thread. I discovered the new cable is not turning when connected to the transmission. As I have played with the cable and changing gears for the speedo cable ( have 3.10 rear gears + - just eyeballing it). While the car is on jack stands starting and putting into gear to run the rear axle we have used a 19 tooth gear and a 22 tooth but the real issue is the driven gear does not mesh with the transmission output shaft drive gear. it is out of place by about at least 1/2" forward on the shaft. From what I can see the retainer clip is in there and the drive gear looks like its orange so I think I have the correct parts for my application.

The car had the turbo 350 trans either repaired or replaced before we bought the car as it is very clean compared to the rest of the drive train.
Is it possible the wrong tail housing was used on the transmission or could it be something simple like the speedo drive gear just walked up the shaft? I plan on pulling the tail housing off next weekend to get a better look.

Thanks for the help.

TimAT

The output shaft on a TH 350 has 2 possible locations for the speedo drive gear. It's easy-- and I mean REAL easy to put the gear in the wrong location.. Pull the driven gear adapter out and look in the hole. The drive gear should be centered in there. Next thing to look at is the square drive on the driven gear- (speedo cable end of the gear). Sometimes if the cruise control transducer locks up, and it sounds like your may have from your description, it will round out the end of the driven gear.

JillsVette

Tim,
Based on your description the output shaft gear is in the wrong location. It appears to be at least 1/2 inch forward of the hole to be lined up. I ordered 2 new gears . 1 orange 8 tooth drive gear and 1 19 tooth driven gear and a new retainer clip. Once those parts arrive i will remove the tail housing and change the drive gear location. Happy to hear that it could be that simple to repair. Thank you for your reply..

Matt

TimAT

When you get the tailhousing off, use a small screwdriver to hold the tab on the clip down, then I use a wrench big enough to fit over the tailshaft and use that to drive the gear off. Seems like it takes 4 hands, but 2 will do. Hold that tab down, then use the shaft as a guide for the wrench and tap toward the rear. Sounds bad, but it's really pretty easy.

JillsVette

Wow. This speedo fix has taken me on a wild adventure and cost a grand to fix. I removed the tail housing and found that the Speedo gear had slid up the shaft about a half an inch the clip was broken after removing the housing I found at the rear bushing in the housing was bad so I had that replaced. then when testing the new speedo once it was put back together On jack stands we found that the trailing arm bushings were shot also the passenger side rear wheel bearing was howling so that let us to tear the entire rear suspension apart replace the U-joints in the half shafts and put in two rebuilt trailing arms from Vtech corvette now that the car is all back together the horn doesn't work see another thread for that Adventure

bazza77

Yes indeed , welcome to old corvettes

BTW , you know you shouldn't run the car in drive while its on jack stands , as the hanging half shafts can cause the uni,s to bind up.

JillsVette

That is good to know. It was just a quick drop in gear hear a "bang " from the trailing arms and turned off. lol. Its still on stands until the tires are replaced and I get the horn fixed. My wife is bugging me to get it done so it will be on the ground soon. Thanks for the info