speedo & AOD

[marton]

Hi,

I bought a renovated AOD for my 92 Mustang 5.0 LX from don@transmissioncenter.net, now installed and works fine. I have the standard diff, wheels and tires. But when my speedo is showing 65mph my GPS is showing 80mph.

I do not see what could have changed to effect the speed reading, anybody got an idea?
I sent an email to don@transmissioncenter.net today, but am also interested in your views.

I did some searches here and somebody mentioned the 90 -93 Mustang need a gear reduction box to have an accurate speedo. I could not find any details of this in my Haynes, or Chilton or on this site. Somebody gave a link to year one
http://www.yearone.com/serverfiles/f...GO.x=7&GO.y=13 but I do not see anything called a gear reduction box....

Regards,

Marton

[Jeff Chambers]

Yep, depends on what vehicle and what year the rebuild AOD orignally came from. The drive gear is actually machined onto the output shaft of the AOD so its not possible to change it without tearing the tranny down and replacing the output shaft. Now if you can figure out what output shaft is in the trans, you can match the driven gear for a correct reading. Driven gears are cheap, so you just might buy one in each direction of where you're at now and give them a try. It only takes a few minutes to change out a driven gear.

See here http://www.crt-performance.com/speedometers.htm for more information.

[marton]

Hi Jeff,

Many thanks, excellent link - good idea to try driven gears each side of the one that I have.

Looks easy to change

Thanks again

Marton

[~The Jester~]

I saw the title of this post in the list, and I was already thinking Jeff's link before I even clicked on it.

GOOD info on that whole site. Browse around in there sometime ya get a minute.

[marton]

Happy ending

Thanks guys, you were all correct.
don@transmissioncenter.net who supplied the gearbox sent me free of charge a blue speedo gear and that fixed the problem.
I had the official Swiss Government 3 year vehicle test today and it passed the speedo check. Surprised me because according to my GPS it is still 5% slow.

Just to be safe and to be sure I got the part before the official Swiss Government 3 year vehicle test, I also ordered a blue gear from http://www.crt-performance.com/speedometers.htm. They were very helpful and it also arrived in time.

So I guess I will be laying some speedo gears into ebay today.....

Marton