Replacing Speedometer Gear

[FordF-SuperDuty]

I've been thinking about putting bigger tires on my Bronco and I want to keep the speedometer accurate, has anybody ever changer one? What is involved and is there a write up you could point me to?

 

[countryboytn]

If you aren't going alot bigger, I wouldnt worry with it... some aren't even close from the factory. Given, our Lumina is a Chevy... but it is off by about 4mph. according to our GPS.

Aslong as it's within 5ish, you shouldnt have to worry... just run the speedlimit.

 

[FordF-SuperDuty]

If you aren't going alot bigger, I wouldnt worry with it... some aren't even close from the factory. Given, our Lumina is a Chevy... but it is off by about 4mph. according to our GPS.

Aslong as it's within 5ish, you shouldnt have to worry... just run the speedlimit.

Speedometers are always off, and technically GPS is off, very slightly. It came with 235s stock and it has 255s on it currently so I don't know if it was changed out when the tire sized was increased.

 

[O'Rattlecan]

Taylor, I'm not entirely sure yours has a gear. In 1988 I'd have to look in my book but I think your speed sensor is on the side of the transmission and it is electronic.... Maybe not for AOD.

Ryan

 

[countryboytn]

Speedometers are always off, and technically GPS is off, very slightly. It came with 235s stock and it has 255s on it currently so I don't know if it was changed out when the tire sized was increased.

I realize, they are always off... but +/- 4mph, seems like alot to me..

and GPS's are probably pretty close (within a couple MPH, I would think) but they don't updated real time... It always says 4mph under though... speedo says 40, gps says 35... speedo says 65, GPS says 60...ect.

 

[Skandocious]

Ryan I'm pretty sure all gen 8's use a gear.

Taylor I tend to agree that it might be kind of pointless to change the gear but if you want the procedure then I'm sure we can dig it up somewhere-- I've never done one but I imagine it's not that hard.

 

[FordF-SuperDuty]

Taylor, I'm not entirely sure yours has a gear. In 1988 I'd have to look in my book but I think your speed sensor is on the side of the transmission and it is electronic.... Maybe not for AOD.

Ryan

I'm pretty sure that both automatic transmissions for 88 were non-electronic. If it is the case would the sensor auto-calibrate?

 

[FordF-SuperDuty]

Oh, if I were going to change tire size it would be 32".

 

[countryboytn]

Oh, if I were going to change tire size it would be 32".

I personally wouldnt worry with it then... if you was going 35's+ it may need it, but I don't think 32's will.

 

[Blue Goose]

There's nothing to it, Taylor. I used to take the gear off of your Grandpa's Bronco II when they'd "dingy tow" it behind the motor home every winter going to Florida. I would do that so the mileage didn't rack up on the Bronco II and run it out of warranty.

 

[conanski]

Since the truck came with 235's that's going to be a rather large step up in tire size and both the speedo and odometer will be way off which means your milage is going to appear to go down quite a bit. Changing the speedo drive gear is simple you just have to choose the right gear, but you're also going to find those tires make the truck pretty doggy, a gear change to 4.10's would put everything back to the stock overall drive ratio and elminate the need for a speedo recalibration.

 

[FordF-SuperDuty]

Since the truck came with 235's that's going to be a rather large step up in tire size and both the speedo and odometer will be way off which means your milage is going to appear to go down quite a bit. Changing the speedo drive gear is simple you just have to choose the right gear, but you're also going to find those tires make the truck pretty doggy, a gear change to 4.10's would put everything back to the stock overall drive ratio and elminate the need for a speedo recalibration.

It would be nice to have 4.10s, but I can't afford a a regear but 3.55s and 32"s should make it that doggy.

 

[FordF-SuperDuty]

Where is the gear located I'm guessing it's either in the dash, tranny, or rearend?

 

[Blue Goose]

None of the above......It's in the tail shaft of the transfer case.

 

[FordF-SuperDuty]

Would I need a new odo gear too or would the speedo gear take care of that/

 

[Blue Goose]

Just the nylon gear that goes on the end of the cable.