Speedo Question

[wheelman21]

I have a 727 mated to a 340 that has allegedly been reprogrammed, and is coupled to a 3.91 gear rear. Any idea how far off my speedo is? And how hard is it if I need to put a new speedo gear in?

 

[fishy68]

No possible way to know because

1. you didn't way what gears your car had or what speedo pinion gear it has now.

2. you didn't say how tall the tires are. That has to be known.

3. the speedometer itself can be way off sometimes so even if you have the correct speedo gear it may not be right.

Easy way to tell is put a GPS in it and see what it says.

Changing the speedo gear is real easy. Especially if you have a rack. Takes me about 20-25 minutes to swap one if I don't have a rack. 15 minutes with a rack.

 

[Tony Fields]

I have a 727 mated to a 340 that has allegedly been reprogrammed, and is coupled to a 3.91 gear rear. Any idea how far off my speedo is? And how hard is it if I need to put a new speedo gear in?

Here's a speedo gear chart...you will need your rear tire diameter

Unhook your speedo cable at the tranny. remove the hex bolt holding the
clamp around the speedo adapter and pull out the adapter. The speedo gear
will come out with it. Check the number of teeth on the gear...should be stamped on the side. With the chart I have included you can see which
gear you need for the 3.91 rear end and your tire size. If you need something
other than what you removed you will need to purchase the correct gear. There
are several members here that sell them. When you install everything make sure
that the number that corresponds to your tooth count is at the 06:00 position
before you tighten the bolt. The reason for this is that the gear center on the adapter is not on center. This is because the gears have different diameters depending on their tooth count. In rotating the adapter to the correct position, the teeth will be in contact with the mating pinion on the
tranny shaft.

One more thing.....you may spill some fluid when you pull the assembly out
of the tranny......be ready just in case.

 

[bOb shingler]

hey tony, could you e-mail that chart to me?

 

[Bad Sport]

Bob all you have to do is right click on the image and save it to your computer. Here is some other info for you in regards to changing the gear.

 

[wheelman21]

Bob all you have to do is right click on the image and save it to your computer. Here is some other info for you in regards to changing the gear.

Thank you for that picture. I realized the last guy who had this transmission had put some type of black silicone sealant in the adapter plate. I'm glad that comes out, so I can pop it out and clean it. I was afraid I was screwed! I'm not going to lose my fluid when I pull that am I?

 

[Tony Fields]

If you lose any fluid, it should be a small amount.....just wanted you to be ready
so you didn't jump and bang your head.:yawinkle:

 

[Bad Sport]

Jack up the left side of the car and place a couple of jack stands under it, you won't lose a whole bunch.