I have a 78 pinto that started life as a 2300 c3 and the rear tag says 3.08 gears. I have since converted it to the stock 4sp tranny and now the speedo is of by 20%. When the car is doing 60mph the speedo reads 75mph. How can i correct this? The driven gear is a green 17tooth and if I figure correct going to a 18t is only a change of 6%.
I would have though since the rear wasn't changed the speedo gear would have been still correct. Must be the drive gear on the tailshaft is differant?
Any suggestions?
BTW it sure changed the slug into a screemin demon. More like by old 77 was. :fastcar:
Quote from: onefarmer on December 06, 2007, 11:08:55 AM
...I would have though since the rear wasn't changed the speedo gear would have been still correct. Must be the drive gear on the tailshaft is differant?...
The 4spd has a 1 to 1 fourth gear, the same as the C3's 3rd (from what I have found), so I would think there is a difference in the A/T eating some power (maybe).
Bill
Quote from: 77turbopinto on December 06, 2007, 12:23:12 PM
The 4spd has a 1 to 1 fourth gear, the same as the C3's 3rd (from what I have found), so I would think there is a difference in the A/T eating some power (maybe).
Bill
The auto definitely eats power. Way back when I was working on a pinto with an auto. While it was running I added tranny fluid and the rpm's dropped by over 200 and that is just to run the pump
I agree that the 4sp and the a/t have a 1:1 final drive, but with all trannys the speedo is run off the tail shaft, read driveshaft. So the tranny type should not have an effect on the speedo. So it has to be in the speedo gearing. Do I just need to find the correct driven gear and to which one? Or do I need to change the drive gear and to which one?
Glads I put the 'maybe' in there.
The only thing I can think of is the gear IN the tranny.
Bill
OneFarmer, Here check this out
Quotehttp://www.flemworld.com/Hto/rear.html
This info was provided to me from Pintony.
You need a 20 something tooth. My 8" with 3.00 has the Purple one.
High_Horse
Thanks High Horse looks like just what I need. I'll go check it out!
High Horse, According to your chart I put in a 21T speedo gear and it seems to have been the answer. Now I gotta get it out on the freeway and check it against the mile markers.
Hey onefarmer,
Let us know how your results turn out!!!
Quote from: Pintony on December 19, 2007, 06:43:58 AM
Hey onefarmer,
Let us know how your results turn out!!!
I will if I can ever cure the fuel issues! >:(
See more on that over here.
http://www.fordpinto.com/smf/index.php/topic,8611.0.html
I'm sorry, but I saw "Speedo Help" & all I could think of is If you MUST wear a Speedo, baby oil is your friend :)
Quote from: crazyhorse on December 20, 2007, 01:39:39 PM
I'm sorry, but I saw "Speedo Help" & all I could think of is If you MUST wear a Speedo, baby oil is your friend :)
I'm startin to feel an itch :o ;D
Quote from: Pintony on December 19, 2007, 06:43:58 AM
Hey onefarmer,
Let us know how your results turn out!!!
I finally was able to get out on the freeway. I went 10 miles and the odometer went 10.45. So looks like I'm still off by 4.5%.
Using this when my speedo shows 70mph I'm really going 66.85mph. According to the cars passing me that's about what I was doing. I figure I need a 22T driven gear but don't see any of them so, I'm going to need to change out the 8T drive gear for a 7T. Great more work! :rolleye:
What size tires do you have on there? That might be part of it.
I currently have bias ply snow tires. The equivilent of P175/78-13. They have only been on it for 20 years and still like new. I guess I could go up to a 14" but I have some alum slot wheels I want to use. I put them on the front and like the looks. To see the car go here. http://my.voyager.net/~ancestorfarms/pintoinshop1.jpg
WOW! :surprised:
Not too sure I'd trust 20 yr old tires, especially snows. And especially at freeway speeds!!
New snows will come apart at highway speeds.
I think my 79 has tires almost 20 years old on it too. But it sat in a garage for the last 1 of those years. It still needs new ones, tho. 200 will get a new set of tires, not the cheapies but next to the cheapies. (i will NOT buy the cheapies). I use Douglas Xtratrac from walmarts tire & lube express. P175 80 R13.
OneFarmer,
Heck.......If your tires are the stockers then go with the 23 tooth gear....I thought you had bigger tires.
High_Horse
**Update**
I tried the 23T and instead of being 4.5% off it's now 10% off the other way. Can't win :o. I'll just have to wait untill I can pull the trany and change out the drive gear. ::)