Tachometer, RPM's and larger rear tires and speedo
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More Turbo
Joined: Sep 2015
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Tachometer, RPM's and larger rear tires and speedo
My speedometer reads 5 MPH low at all speeds. I believe we discerned I have a 2.75 rear axle ratio on a previous post.
I have a 3.25 posi to install later. I plan on putting tall mud tires on the rear to compensate for the low gear ratio some. I do not
believe I have seen any 16" 5 lug wheels for the large Ford pattern. I hate not knowing the engine RPM's. Anyone
have an electronic tach they'd recommend? (cheap) My current tire size is 235 75 15
Does this 3 speed top loader have a replaceable gear on the speedo shaft to correct the speedo?
I have a 3.25 posi to install later. I plan on putting tall mud tires on the rear to compensate for the low gear ratio some. I do not
believe I have seen any 16" 5 lug wheels for the large Ford pattern. I hate not knowing the engine RPM's. Anyone
have an electronic tach they'd recommend? (cheap) My current tire size is 235 75 15
Does this 3 speed top loader have a replaceable gear on the speedo shaft to correct the speedo?
Moderator
Joined: Jan 2001
Posts: 56,997
Likes: 2,742
From: Virginia
Have you driven this truck yet? I would not consider 3.25 to be unusually low. I have driven several trucks over the years with 3.50 gears in the back, and they did fine for overall use. Revving a little high on the interstate if you want to go 70mph, but if you are going to be mostly driving 55 mph they are perfectly fine. 3.25 would do even better on the highway at speed. 2.75 would be like driving a modern truck with overdrive, though you would be in overdrive all the time (lesser towing ability).
Any cheap tach from Amazon should work, as long as it's convertible from 4, 6 or 8 cylinder engines. Most have a switch on them.
Any cheap tach from Amazon should work, as long as it's convertible from 4, 6 or 8 cylinder engines. Most have a switch on them.
FTE Legend
Joined: Nov 2015
Posts: 30,938
Likes: 4,124
From: Angier, NC
I can tell you a 2.75 gear is not that great and I have a granny 4 speed.
If pulling a heavy load or trailer and you have the 3 sped you would be looking at early clutch replacememnt
Even empty and starting off in 2nd gear is not great but the 300 has a lot of pull down low and I can let the clutch out at almost idle when taking off.
As for your speedo gear question I dont have a answer but I can tell you the manual T18 & NP435 both use the same gear on the end (driven) and also inside the transmission (drive) as I had to swap them from the T18, I replaced them to get the speedo to work. And when the NP435 went in I found the speedo not working again and the drive gear in the transmission was bad so I just swapped them.
With that I would say they may all be the same for the manuals but you will have to check to make sure.
Gary has the speedo gear info. on his site with part numbers and the gear colors IIRC. I got my replacement off Ebay and at the time seen you could buy assortment of like 3 gears if you did not know what one you need.
Dave ----
If pulling a heavy load or trailer and you have the 3 sped you would be looking at early clutch replacememnt
Even empty and starting off in 2nd gear is not great but the 300 has a lot of pull down low and I can let the clutch out at almost idle when taking off.
As for your speedo gear question I dont have a answer but I can tell you the manual T18 & NP435 both use the same gear on the end (driven) and also inside the transmission (drive) as I had to swap them from the T18, I replaced them to get the speedo to work. And when the NP435 went in I found the speedo not working again and the drive gear in the transmission was bad so I just swapped them.
With that I would say they may all be the same for the manuals but you will have to check to make sure.
Gary has the speedo gear info. on his site with part numbers and the gear colors IIRC. I got my replacement off Ebay and at the time seen you could buy assortment of like 3 gears if you did not know what one you need.
Dave ----
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