Still looking for why

[vacavillebob]

I posted this about 2 years ago but still have not figured out why it does what it does, of how to fix it. I took out a power glide trans in my 70 monte and installed a 200r4. The speedometer does not register anything, UNLESS I am coasting in neutral. Then the speedometer reads the same as the GPS speed.

 

I am open to any suggestions. Thank you, Bob

[monte70car]

Take a look at the speedo cable. Make sure its plugged into the back of the cluster all the way. It sounds like the cable is not keeping a good connection.

[Sam (Bones)]

you can use a drill on the speedo cable to try to determine if it's the cable/speedo or in the trans

[vacavillebob]

I have checked the cable it is fine. I have checked both ends to make sure it is connecting as it should. But like I said it works fine as long as I am in neutral coasting and it reads the same MPH as the GPS. But thank you.

[montefrazer]

If the cable and connections are good, all that's left is the drive gear on the output shaft and the driven gear it runs. Maybe misaligned or teeth worn? Had a problem with the drive gear on a turbo 350 once. Wouldn't stay in place on the output shaft. Repositioning it several times before putting in a new one. That fixed it.

[footballubet]

Sounds like time to yank that gear out and check the teeth and make sure the drive gear doesn't turn on the output shaft.

[wallaby]

That's a good one. The drive gears are on the output shaft and rotate whenever the car is in motion, regardless of what gear it's in. I can't figure why it only registers on the dash when the selector is in the neutral position.

Is it possible that the linkage or column rotation is somehow disrupting the input in other gear positions?

 

Maybe the trick is to disconnect the cable from the trans and drive it with a drill as mentioned....then try moving the gear selector to different positions (all with the engine off). At least this way you can figure if the problem is inside the trans or not.

[vacavillebob]

Well I pulled the gear out and it is in great condition. But next time I have the car up on my friends rack I will try your recommendation Mark. Maybe that will tell me more. Thank you, Bob

[stangeba]

Is everything else stock like dash speedometer and no speed control and a one piece speedometer cable? No fancy electronic speedometer.

I once cut my inner speedometer cable too long and had to leave the cable loose, at the speed control unit, or the speedometer wouldn't work.

Bruce

[vacavillebob]

Hi Bruce: Yes everything is stock accept the transmission. The cable is one piece and was used on the old transmission. I have seen on the internet that a lot of other people have had this problem. But not one has ever posted how they cured the problem.

[amsterdam84]

You can try testing by disconnecting the cable at the trans and using a drill spinning the cable. With the car off try different gears. If it still does it its in the speedo.

[wallaby]

You can try testing by disconnecting the cable at the trans and using a drill spinning the cable. With the car off try different gears. If it still does it its in the speedo.

 

Originally Posted By: wallaby

Maybe the trick is to disconnect the cable from the trans and drive it with a drill as mentioned....then try moving the gear selector to different positions (all with the engine off). At least this way you can figure if the problem is inside the trans or not.

 

There's a great idea.

[amsterdam84]

Hah how did I miss that you said the same thing? That's what I get for typing that out on my phone while walking the dog.