1980 Automatic Transmission

Hello again all.

I have a 1980 Plymouth Arrow 2.6 Sport. Automatic. OK.

How do I determine which automatic came in it? I think there are two different types or is there just the one?
Because of the 3:55 rear end I put in it my speedo is reading a little slow. Probably 5-7 miles slow at highway speeds. It's not too
bad in the city.

Anyone know the stock pinion number of teeth it came with before I take it off?

Thank you.

Obviously the stock rear end was a 3:909 or a 3:91.

There is a chart in the 1980 manual that gives all the speedo gear teeth for all tranny / rear axle ratios. You have the Aisin / Warner "baby " 904 3 speed automatic. It may be hard to find the right speedo gear, as they were dealer only, and I don't think the 3.55 and auto combo was popular, if even offered. There is another chart that was in the John Baker catalog that showed the gear ratios and tire size that could be used to fool the speedo close to stock, or there are speedo adaptors that go between the tranny and speedo to correct for the difference - I will try to find the info, or look on street roDDER FORUMS, AS THEY HAVE TO DO THIS ALL THE TIME. Sorry for the caps.

Quote:

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Originally Posted by pennyman1

There is a chart in the 1980 manual that gives all the speedo gear teeth for all tranny / rear axle ratios. You have the Aisin / Warner "baby " 904 3 speed automatic. It may be hard to find the right speedo gear, as they were dealer only, and I don't think the 3.55 and auto combo was popular, if even offered. There is another chart that was in the John Baker catalog that showed the gear ratios and tire size that could be used to fool the speedo close to stock, or there are speedo adaptors that go between the tranny and speedo to correct for the difference - I will try to find the info, or look on street roDDER FORUMS, AS THEY HAVE TO DO THIS ALL THE TIME. Sorry for the caps.

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Thanks. It's appreciated.

I found this but not the right size. Would I have to look for more or less teeth?

http://www.ebay.com/itm/Mopar-Speedo...Pz7Lgw&vxp=mtr

Excellent condition, used factory Chrysler speedo pinion part number 2538931 has 31 teeth, fits 1966 through 1976 Torqueflite 727 & 904, A833 4-speed and A903 & A745 3-speed manual transmissions. Applications are: 3.55 ratio with 30“ OD tire, 3.23 ratio with 28” OD tire and 2.93 ratio with 25” OD tire. Pinion seal and adapter O-ring also available as well as the metal speedo pinion adapter which the speedo cable attaches to. Shipping $ 7.55 via Priority Mail; we ship purchases twice weekly, Wednesdays and Saturdays. For a copy of our enhanced speedo pinion selection chart or technical information contact us. Most Torqueflite 727 & 904

I have a 3:55 with a 25" OD wheel.