Speedometer gear question

[deanster]

I swapped transmissions from 904 to 727 and now my speedometer is reading fast. Will the gear from the 904 fit in the 727? Thanks...Dean

 

[Duster346]

Yes it will.

Somewhat strange that your speedo would be off, as it more relates to tire size and rear gear ratio.

 

[myasylum]

I went to a /6 904 to a V-8 904 and the speedo is off 10mph.
Is there a gear I should get for that?

(sorry to steal your thread)

 

[yellowdartdave]

It all depends what rear end ratio the transplanted tranny was set up for.

 

[Duster346]

Right.

Post you tire size and rear gear ratio and we can figure out what speedo gear you need. There are some calculators online. I have a pretty good calculator on my computer at work that is within 2 mph.

 

[myasylum]

Ah, I see! Good point! So if I have 3.21 gears, I'd have to look for a 904 gear that matched 3.21 rear end. Do you know where I can find these gears?

(oh, just read above post!)

I have 265/50/15's with a 3.21 rear end.

thanks!

 

[deanster]

My rear end has 2.76 gears. I guess the donor car had 2.42 gears. Thanks for the answers. I'll change it out tomorrow....Dean

 

[dusterforever]

I swapped transmissions from 904 to 727 and now my speedometer is reading fast. Will the gear from the 904 fit in the 727? Thanks...Dean

I used this chart and I am within one mile per hour...hope this works...on
moparts...Dusterforever

http://www.moparts.org/Tech/tech/pages/speedo.html

 

[SwingerDeluxe]

Right.

Post you tire size and rear gear ratio and we can figure out what speedo gear you need. There are some calculators online. I have a pretty good calculator on my computer at work that is within 2 mph.

Duster346, I'm wondering if you could compute the gear I would need? I have replaced the rearend with a 8 3/4 with a 3.23 ratio and have 205/70/14's tires. Thanks for any help! Bill