Manual Transmission speed sensor

I wanted to know how many pulses from the speed sensor per revolution of the drive shaft I should see on my 08 Tacoma base model, manual transmission, 2.7 Ltr 4 cyl truck.

I could swear someone said it was 4 per revolution. I was anticipating 180 pulses per second at 60 MPH but was surprised to get 68. NOT what I was expecting at all.

I crawled under and marked the shaft with tape, marker and a pointer, then rotated the shaft. I got a very odd number. Seemed at one revolution I would get two pulses. So I double checked and got only one. This was odd. Is this correct? Three pulses per every TWO revolutions?

I'm still grappling with my speedometer issue. I know I can just get a Dakota Digital signal modifier and install it, but that's over $90. Yeah, I know that's not much. But when you're not working and on a very small fixed income, yes, it is kind of big.

So when armed with solid information (tests seem to suggest I want to convert down to 11/12ths. An odd number, so a simple pulse divider network isn't going to get me there. I need to convert frequency to voltage then back again. While at the voltage stage I can easily modify the voltage with a simple voltage divider network. Easy to dial in and get a correct speedo.

BTW: My odometer adds an extra mile every 28. Go 28, read 29. And I have the right tires and gears on the truck. Very exasperating problem. I hear lots of Tacoma's have this issue. No wonder Toyotas go further than other cars. They only APPEAR to go further.

Dirty trick if you ask me.

Back to the original question: How many pulses per revolution from the speed sensor is correct?

Thanks.

 

you're speedo stock will read 65 but be going 60. I checked this on mine with GPS. The ODOMETER will read correct though.

If you are getting a 3% error on the odometer, you could go 1 tooth higher.. to a point.

Looking at the pattern through the hole where the gear goes, I see multiple spirals, could be 2 per revolution,but on that part of the system, I just don't know.

pull your speedo gear out, if its 29, you can fit a 30T, for like $20 iirc

 

I hear a lot of people say something similar about the speed. However, part of what is bothering me is the mileage. I have an extended warranty. But it will expire faster than what I paid for. 3 1/2% bothers me. (odometer) 8.3% speed error also bugs me.

I'm fairly retentive when it comes to accurate data. Been an engineer (electrical / electronics engineer for NASA) 30 years. Automotive doesn't usually stump me but this is my first go around with Toyota and with the Tacoma.

My wife drove an 89 Celica ST until she wrecked it. She loved it. I hated it. I was under the hood more than behind the dash. But she loved it so I kept it running. Never had any issues with the speedometer or odometer on it, so this is new territory to me.

Oh, and thanks for the picture. I'll check with the Toyota dealer to see if I can get one. Do you know of a better source?

 

Drive on the freeway where you can get 5-10 miles in . Reset tripmeter and see if 10=10 or if 10 odometer = something else. If they match close you're good. The speedometer reads high so Toyota doesn't need to deal with false claims of innacurate speeds vs speeding tickets.

GPS will help confirm data as a 2nd or 3rd source.

 

One quick question, you have 4wd? or 2wd? I jst realized if you don't have the transfer case like I do, 2wd will be different.

 

Actually I did forget to mention it's 4wd.

And driving on the freeway, reset my trip meter at mile marker 300, going north. By marker #328 my odometer tripped to 29 miles almost exactly at the marker. I tried to set my trip meter to zero as close as possible, but because of a slight delay it's difficult to be that accurate. I'm confident that, and I watched as each few markers resulted in an additional tenth of a mile. Between 2 and 3 markers, closer to three. But by the 328th marker the odometer tripped to 29 just about the same distance as when I reset the zero at marker 300. So 29/28ths is just about as accurate as I can get without getting a really really long tape measure.

But come Monday I will be talking to the service department about the gear in the transmission and find out if that IS changeable. I'm confident it is - I see a picture of exactly what I imagined was in there, so - - -.

Oh, and regarding the gear in the picture, do you know of a good source for that part?

Anyway, thanks. Sorry I didn't get back sooner, had a barbecue to go to. And who doesn't love barbecued pizza?!

 

No problem. Reasearch it a tad to confirm. Pull off your gear holder and check the teeth. Its held on by a single bolt and pulls off easy. you have 3 maybe 4 choices that can fit into it 27?, 28, 29, and 30. 31 is too big. You Likely 29, maybe 28. you have about 3% high and adding 1 tooth would fix that almost spot on.

link below is boring stuff, but gets you a part number. To swap, its easier than an oil change .
http://www.toyotapartsoverstock.com...&ukey_driveLine=6724&searchString=speedometer gear

 

Yup! Got an N-29. Just ordered the N-30. I sure hope you're right about this fitting. The numbers work nicely but I'm just worried that I'll have to modify something just to make this fit.

You say you did this? Was there any problems?

 

zero problems, 30T went in fine, but a 32T would not press in.

make sure of the following though:

Try to tilt the truck with the gear up a bit, some oil comes out, but not a lot.

keep parts on clean bag or such as they will be oily

the end has 2 prongs, make sure they seat by turning the gear

make sure the clip seats in the deep groove that holds it in place

place in the training pin

pull gear to make sure its seated

Then just press in the gear assembly and rebolt down. Once you do it you will find that its really easy, its just the detail missed that can mess you up.

 

Thanks. It was a pleasure pulling the sensor and gear assembly out with the removal of a single 12mm bolt. Unsnapped the clip and removed the gear and shaft to get a look at how it goes together. Had an oil pan under the truck to catch anything that came out. Got about a half cup of oil, no more than that. Reassembly was as easy as disassembly.

Now I have to wait till the new gear gets here. Once I put it in I'll do another set of tests for mileage AND speed. There's still a chance that if I want the speedometer to be accurate I may have to install one of those "Dakota Digital" signal processors (SGI-5 C). But if it's close enough and the error slope is manageable I may just reposition the pointer on the speedo.

My biggest concern is the mileage. Once that's corrected changing the position of the speedometer needle is stupidly easy. As easy (almost) as swapping the sensor gear.

Anyway, thanks tons for all your assistance. If you were close by I'd have you over for beer and pizza. Ever barbecue pizza? Entirely different experience from oven baking. Try it first with a 'Papa Murphy' pizza. You WILL need a pizza stone for the grill and you will have to close the cover. Otherwise you'll burn the bottom and the top will still be raw.

Here on Tacoma world. Where else can you learn such things?

'av'a g'day mate.

Thanks again.

Tony.

 

No problem. Grilled pizza sounds damn good too.

 

Once you get the gear on the speed sensor taken care of the speedometer will follow suit. It bases it's output on the signal from the speed sensor.

 

Thanks for the reply. The speed gear will result in a 3.48% correction. My speedometer is off by more than 7%.

One thing I have noticed is the slope of the error (I do a lot of charting). I'm hoping the change (and I will probably try running the numbers to see) but I'm hoping the change will flatten it out. That way a simple repositioning of the needle may be all I need to bring it into full accuracy.

I'm a stickler for accuracy. Always have been. Many people I've worked with have hated that about me. Good enough was never good enough. It had to be right. In my mind, right is right and wrong isn't. I can live with a single MPH or two, not FIVE at 65.

But yes, I know you're right about swinging the accuracy in the right direction. What may be left is just a simple needle correction. They're stupidly easy to change.

Thanks again. And thanks ALL for the help.