SPEEDO CHANGE after gear swap

[nawlins-tim]

After buying this 1980 El camino body and later realizing some already swapped the rear to a 8.5 10 bolt out of an 87 t-type.What I want to know is how do you get the speed-o-meter but to factory settings. I think I could deal with the tire size difference, but the 3.42 is throwing of the speed big time. Can a rookie handle the trans work?

 

[Bonnewagon]

Where the speedo cable hooks to the trans is where the gear is. You figure what gear will work by using the gear calculator and just swap it in. With automatics you may need to change the gear carrier too, it only fits certain ranges of gears. I have a link or two. http://www.wallaceracing.com/speedo-calculator.phpand this http://www.novaresource.org/speedo.htm and this http://www.tciauto.com/Products/TechInfo/speedo_gears.asp TCI sells the gears too.

 

[megaladon6]

is it a th350 or a 200-4r

 

[nawlins-tim]

It's a Th350 ,and just yesterday I noticed a leak at the speed- o cable. Tried to tighten it , and it got tight but seems the the "Bullet"(is that what U call it)is still loose. I guess I need to check the o-ring or make a gasket . Or buy a whole new Bullet assembly with the new driven gear.
When I am trying to come up with the Drive+Driven gear combination how do I tell which drive gear I have. Will I be able to actually count the grooves on the gear when it is still in the car? Or can I go by the color code? I found a couple places with the parts I need.

 

[Kiko]

I'm just in the process of making the same change. I had a very small leak in my 700R4 where the speedo cable connects to the housing. The reason for the small leak was the plastic speedometer gear housing. When the speedo cable is tightened hard onto the gear housing, it deforms the plastic and over time the threads get worn or chipped. I would suggest getting a new aluminum housing with a new "O"-ring seal.

When you remove the housing, you'll see the shaft and gear. At that point you can actually take the gear out and count the teeth. The gears are also colour coded. Here's a good reference: http://www.transmissioncenter.net/speedometer_calibration_______va.htm

It's not a hard change and things become quite obvious once you remove the speedometer gear housing.

Good luck and let us know how things work out!
Andry