Trying to figure out which speedometer gear I need with bigger tires
Been searching the forums and can't seem to figure this out correctly....my stock setup is 195/75/15 with a 3.55 gear ratio with a 19 tooth gear. Trying to figure out which speedometer gear will correct my speedometer with 275/45/20's on the truck? Any help would be much appreciated
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What is the OD of the tires? I could figure it myself, just don't have the time.
What transmission do you have? With these 2 items, I can assist in finding the right tooth count gear and part number to get the speedo close. The speedo unit itself has a fine adjustment that may need tweaked to finish the correction. You mention 3.55 gears, so I'm guessing it's an 83-86 with an 8.8 rear axle. |
Didn't I answer this question in another post here?
There are gear calculators out there that will get you into the ballpark for your setup. Here is one I've used before: Speedometer Gear Calculator |
Originally Posted by Rogue_Wulff
(Post 11839417)
What is the OD of the tires? I could figure it myself, just don't have the time.
What transmission do you have? With these 2 items, I can assist in finding the right tooth count gear and part number to get the speedo close. The speedo unit itself has a fine adjustment that may need tweaked to finish the correction. You mention 3.55 gears, so I'm guessing it's an 83-86 with an 8.8 rear axle. |
Wow. Really? Is it that you don't want to work to get the answer your looking for and want RW to do all of it for you or that you are just intentionally ignoring me to be a jerk.
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Originally Posted by lavatan
(Post 11839507)
Wow. Really? Is it that you don't want to work to get the answer your looking for and want RW to do all of it for you or that you are just intentionally ignoring me to be a jerk.
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Sorry. It just seemed like you ignored both posts where I put the link and you wanted the information given to you. I have a problem with someone not willing to put in the research or work when the answer is given to them. Now, if you had questions about how to fill out the calculator I would understand that.
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Originally Posted by GotFord83
(Post 11839503)
OD of the tires in 30.4 and the transmission is AOD yes it's a 83 with a 8.8
With this info, perhaps one of our members who has access to the Master parts catalog (or your local ford dealer) could look up what the factory calls for with this combo. If you have a 2wd, you may still have to try adding or subtracting a tooth from the factory spec gear for the 235/75-15, since I don't think a 31" tire was offered for a 2wd AOD/3.55 combo, if so, it would have likely been in an F250 and I don't know what the equivilent 16"/16.5" tire would be. If it's 4wd, then whatever gear the chart shows for a 31x10.50-15 should be well within the adjustment range of the speedo head. |
Originally Posted by lavatan
(Post 11839567)
Sorry. It just seemed like you ignored both posts where I put the link and you wanted the information given to you. I have a problem with someone not willing to put in the research or work when the answer is given to them. Now, if you had questions about how to fill out the calculator I would understand that.
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What information is it looking for that you don't know?
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Originally Posted by lavatan
(Post 11839599)
What information is it looking for that you don't know?
Especially since I knew there was a chart in the MPC that listed speedo gears by application (trans/tire size/axle ratio). Of course, it's dependant upon a factory standard spec. |
I figured the OP had counted the teeth when he had the truck tore apart. He had the transmission and engine out. That would be real easy to count the teeth then.
From the old post: Hey guys in the middle of swapping the old 5.0 motor for a rebuilt one and putting in a new transmission, now the motor and teams are already out of the truck at this point.....I went from the stock 15's to 20's with a 275/45/20....with having the motor and trans out is there a way to correct my speedometer or do I need to wait until the truck is back up and running? |
It's a two wheel drive....I'm in the process of swapping the motor and trans.....not to mention the older cars is all new ground for me.....so needless to say I'm doing a lot of searching on here and learning a lot....sometimes using the net on the phone isn't the best way...when I try to get the calculator to submit it doesn't do anything for me I think it's not responding on my phone
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I don't know if I said it wrong or maybe I got a little lost in this, but if we are talking about the speedometer gear going into the trans it is a 19 tooth, it's in the first post, I should have separated it better
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OK. Assuming that you have a 7 tooth drive gear and the speedo needs 1000RPMs to get to 60mph the number of teeth on the driven gear is 16.5. I would probably go to a 16. That way you'll be running a bit fast but you won't get a speeding ticket.
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