FJ40 Speedometer Calibration (1 Viewer)

[CBS045]

I own a 77 FJ40 with H55f 5-Speed transmission & 3.7 rear end.
Running BFG ATs on stock rims. When traveling 60 mph measured via GPS, the stock FJ40 speedometer displays 50 mph.

I'm looking for any advise or experiences in modification, adjustment or calibration of this speedometer to make it read more accurate.

 

[Chamba]

Since you obviously have the split case to accommodate the h55, get the Speedo gear from a US spec FJ60. This will raise your 50 mph higher. You don't mention your tire size (brand will not alter speed) if they are stock this will make your Speedo read correctly.

 

[CBS045]

Since you obviously have the split case to accommodate the h55, get the Speedo gear from a US spec FJ60. This will raise your 50 mph higher. You don't mention your tire size (brand will not alter speed) if they are stock this will make your Speedo read correctly.

The tires are 33 inch.
Please excuse my ignorance, but is the FJ60 gear part of the transfer case or the speedometer?
The speedometers for these two vehicles seem to be compleatly different designs,
so I'm trying to visualize where the gear you mentioned is located so I can research it further.

Thanks for your input.

 

[Fast Eddy]

There are a couple different sizes available, but not enough to make up for 20% difference.

http://www.sor.com/catproducts.sor?from=070&part.number=070-01&tabpage=TAB1

There's a guy around here who makes overlays for the speedometer face that would be a much easier solution in any case. It doesn't seem like it would be too hard to do that yourself.

 

[duffontap]

I think the biggest speedo gearing change is about +13%, which would just cover the difference made by your 33" tires, or your 3.7 gears, but not both. I have the same problem and I'm thinking about marking key speeds (35-45-55-65) with a bright dot of paint right on the outside of the glass speedo bezel for quick reference. Easy to do, easy to undo.

 

[Chamba]

The tires are 33 inch.
Please excuse my ignorance, but is the FJ60 gear part of the transfer case or the speedometer?
The speedometers for these two vehicles seem to be compleatly different designs,
so I'm trying to visualize where the gear you mentioned is located so I can research it further.

Thanks for your input.

The gear is on your transfer case where your Speedo cable comes out. As mentioned though, it will make up for the gearing but your tyres will still make it read a bit low. You'll read about 55 when going 60

 

[CBS045]

There are a couple different sizes available, but not enough to make up for 20% difference.

http://www.sor.com/catproducts.sor?from=070&part.number=070-01&tabpage=TAB1

There's a guy around here who makes overlays for the speedometer face that would be a much easier solution in any case. It doesn't seem like it would be too hard to do that yourself.

Thank You for your suggestion and I did follow-up research with the vendor at Spector-Off-Road.
They confirmed what I had suspected and that's that 16 tooth gear I have, needs to stay that way. Changing the gear may work for a while but eventually the nylon will wear down and create a different problem. In my case I would need to go from a 16 tooth gear to a 19 tooth gear in order to achieve a 19.2% correction. This would be a great correction if I could find the part and the mis-match wasn't so great that the gear would probably get destroyed quickly. Your idea could work for a one gear tooth correction for some, but in my case not the logical choice. The overlay idea may be the way to go. I'll create a post and see if anyone can direct me to that alternative source.

 

[CBS045]

I think the biggest speedo gearing change is about +13%, which would just cover the difference made by your 33" tires, or your 3.7 gears, but not both. I have the same problem and I'm thinking about marking key speeds (35-45-55-65) with a bright dot of paint right on the outside of the glass speedo bezel for quick reference. Easy to do, easy to undo.

I know there are repair & calibration shops that work on automotive speedometers. Police cars have "Certified" calibrated speedos even in the older style mechanical days. I know it can be done, just don't know if anyone has tried it with a FJ40 speedo and if so, if it's cost prohibitive. I like the overlay idea because it's clean and neat. I also wanted the calibration idea to work because this vehicle is going to Costa Rica where kilometers per hour is used and I've seen the Tico Police using hand held radar there. My relative got pulled over there and the cops attempted to shake him down for $600 cash. With my Cruiser set up the way it is, it's fast! Highly suseptable to exceeding the national speed limit of 80KPH.

 

[Canarias]

there are knobs on the back of the instrument cluster that look like variable potentiometers. I always assumed these were adjusters for the speedo & tacho - but that was just an assumption. Anyone know what these are for?

 

[bj40green]

- You can change the plastic speedo gear but that will be eaten up by the metal 16 tooth speedo driven gear. You have to replace both gears.

- There is a MUD member here that makes decals for the speedo face plate that you can order to your spec.

- You can pull the speedo needle and replace it at the 10 mark instead of 0.

there are knobs on the back of the instrument cluster that look like variable potentiometers. I always assumed these were adjusters for the speedo & tacho - but that was just an assumption. Anyone know what these are for?

There are no adjustment possibilities on the back of a 40 series cluster. Maybe you're confused by the 5 bulb holders?

Rudi

 

[igniter3]

I have 33 size tires on mine, my speedo read 60mph, I actually traveling at 70mph. If my speedo read 63mph, I actually traveling at 75mph.
I don't think there is such a way to fix this problem.

 

[Canarias]

There are no adjustment possibilities on the back of a 40 series cluster. Maybe you're confused by the 5 bulb holders?

Rudi

I was looking at my 40 speedo a few weeks ago when I noticed this. It´s back in the car now but I have a 45 with the tub off so will have a look at that one and see if it´s the same.

 

[CBS045]

Yesterday I pulled the instrument cluster for general maintenance and cleaning. Upon inspection of the speedometer assembly I noticed a few items of note. There is one minor adjustment part that is designed to center the indicator needle on the zero mark. There is printed on the indicator bezel a calibration specification which says 60 MPH equals 1063 RPM (of the speedometer cable). This clearly indicates there is no adjustment that can be made to the speedometer mechanism as mentioned by Rudi. I also agree with Rudi that the only way to adjust or calibrate the speedometer is by changing both drive gears.

I found that there have been manufactured four different drive gears; 16, 17, 18 and 19 tooth nylon drive gears, and I expect the respective steel worm gear to match. My vehicle currently is using the 16 tooth gear and I've calculated the 19 tooth gear would correct my speedometer variance to within .8%

The next question would be, On what model vehicles were the 17, 18 & 19 tooth parts used?
Then there would be the availability issue of tracking down the used parts.

I'd like to investigate the overlay idea. If anyone can direct me to the individual that makes these, I'd appreciate that information.

If I can't find the overlays, one poster suggested marking the glass. That's always another option.

Thanks to everyone for your suggestions and support.

 

[jbee]

The guy sells the overlays on ebay, you can contact him there. Search 'fj40 gauges'

 

[bj40green]

His MUD name is Biscuit and he's in the vendor section -►https://forum.ih8mud.com/merchandis...edometer-upgrade-non-stock-tires-diffs-4.html

Rudi

 

[Fast Eddy]

- You can pull the speedo needle and replace it at the 10 mark instead of 0.

Then it would be right at exactly one speed. It's not off by x mph, it's off by a percentage.

 

[CBS045]

I checked out the site for the guy that makes the speedometer overlays. His web site says he has a temporary stop in production while he moves into a new location. His products are very interesting and he has a version that is adjusted for 33 inch tires. This would probably get me close to accurate except I also have a different rear end gear ratio. The product is also in MPH where I need KPH, having both would be ideal. I'll contact this manufacturer and see if he'll make a custom overlay for me with specific measurements I prescribe.

I also found out more information on the different speedometer cable drive gears. My calculations indicate that the 6X19 gear would produce an accurate enough indication for my needs, but the 19 tooth gear definitely will not fit the stock worm gear. It's larger in diameter due to the extra teeth.
The Toyota OEM part number for the 19 tooth gear is 33403-69026.

Does anyone know anymore about if there even exist a matching worm gear for the 19 tooth drive gear in the FJ40 transfer case?

 

[Biscuit]

I checked out the site for the guy that makes the speedometer overlays. His web site says he has a temporary stop in production while he moves into a new location. His products are very interesting and he has a version that is adjusted for 33 inch tires. This would probably get me close to accurate except I also have a different rear end gear ratio. The product is also in MPH where I need KPH, having both would be ideal. I'll contact this manufacturer and see if he'll make a custom overlay for me with specific measurements I prescribe.

That's me. I should be back up and running with the vinyl cutter around Oct 1. (Moving to a 25% smaller house caused some interesting issues getting space to get the project bench setup, but the vinyl cutter does not have a permanent home next to my desk).

 

[BallVice]

Hey all - is there a post out here on replacing the gear?

Do you have to drain all the oil from the xfer case when doing it?

TIA!

Frank