8052JZ

iTrader: (13)

As I'm going through with my th400 swap, one thing on my mind is getting the speed sensor to work with the cluster. Just like swapping in an r154, one would get the Marlin Crawler VSS adapter to convert the mechanical cable driven speed sensor to a digital signal. I find the same solution for the GM trans but not sure if it will work with our clusters? Rather than messing with a Dikotal Digital box can this be used instead? Anybody have any thoughts on this?

http://www.dakotadigital.com/index.c...916/prd916.htm

Instruction for it
http://www.dakotadigital.com/pdf/sen-01-128.pdf

And the Specs on the Toyota speed sensor..
http://wilbo666.pbworks.com/w/page/5...peed%20Sensors

SCereal

iTrader: (4)

The hang up I see is the frequency. That mech adapter you linked puts out 40 pulses/rev and toyota looking for 4. If it accepted the input, your speedo would read 10x as fast.

Other ideas and I don't know if its even possible is to route it through the ECU and maybe have it scale it and feed the speedo?

SP uses the dakota digital boxes in their GM auto swap kits and that's what I'm planning to use when I finally get to my 4l80e swap.

8052JZ

iTrader: (13)

Yea that's what my concern was as well. I also saw on ebay that they have one that is a 8 pulse generator for around $20. I might just pick it up and see if I can take it apart. If its an 8 pulse generator, I would assume it has an 8 tooth gear in it?

I do have the dikota digital box on hand but just seeing if there is a better and easier option than that.

http://www.ebay.com/itm/Speedometer-sender-GM-type-transimssion-8-pulse-rev-generator-Hall-effect-/261144001352?hash=item3ccd653b48&vxp=mtr

SCereal

iTrader: (4)

That 8 pulse unit I think you could work with. Then you just need a frequency divider circuit to cut it in half.

http://www.gadgetronicx.com/frequenc...-ic555-ic4013/

something like that should get you started.

Otherwise like you said, maybe you can pull that apart and fill in half the gaps or something. I don't know that I'd trust any of this to feed the ECU for shift control but i assume you're going to a manual valve body and this is solely to run the speedo.

8052JZ

iTrader: (13)

yes you are correct. I am running a manual valve body and just want the speedo to work.

Also, I did notice you can change out the driven speedo gears. I wonder if you can get a different gear to compensate for the 8 pulse sensor to read slower and make it read the correct speed.

Ali SC3

iTrader: (10)

if you want to divide pulses, you don't need to do it mechanically, you can do it electronically.
obviously it does sound like removing 4 fins off the GM sensor would get it close if the GM has similar gear ratios.
you may want to look into how the ratios might affect the speed I know alot of GM trans have different ratios with different rear end ratios to match those than our cars which might throw off hte calculation some, but I am sure lots of people have swapped th400 with speed sensor working but I bet almost all of them use a dakota box.

see this speed cut circuit here
http://alltrac.net/phpBB2/files/spee...t_defender.png

basically the ouput pin divides the pulses on the input pin by a certain amount.
this circuit can divide by 1/2, and a bunch of other types of division etc... depending on which output pin you use.
here is the part number for hte op amp that does the magic "74LS93"
If you look at the data sheet for the op amp, it tells you which pins are divide by 2 etc..
http://www.futurlec.com/74LS/74LS93.shtml
people use this on manual trans cars cause it still gives some speed signal to the ecu (so it knows when you are stopped and when you are moving) and since you divide the pulses by 1/2, you can go to 300km/h instead of 150km/h on the jdm ecu.

if yo use this on an auto car though on the signal going to the ecu with a toyota sensor, it will mess up all the shifting when dividing the proper signal by 2 so don't try that to eliminate speed cut on a stock auto toyota, only can eliminate speed cut on manual trans.
If you do use it to divide the GM signal so that it perfectly matches the toyota signal somehow, then I dont see why it wouldn't work to the ecu and cluster and control the trans properly, again it would have to be a pretty good match and that might be difficult.



you can see how this would work for dividing 8 pulses into 4, and the unused output pins Qb, Qc and Qd are other numbers you can divide the input by.
I'll let you guys piece together the rest of the bits =)

8052JZ

iTrader: (13)

Ali thanks for the info.. Seems to be the dakota box will be easier lol

On a side note! I did find an interesting read on yellowbullet. Apparently the AEM can be calibrated to read the gm speed sensor without the DD box? If the AEM can do this, does that mean the Speedo will read the same?

http://www.yellowbullet.com/forum/sh...d.php?t=569888

Ali SC3

iTrader: (10)

I just assumed you were talking about a stock ecu. the aem can read most speed sensors, just have to set it up in the software.
you might have to set up an output pin to have run the stock speedo for the cluster and re-wire it as normally that comes from the transmission, but the aem should be able to output a different speedo signal than is input, in theory.

8052JZ

iTrader: (13)

So I did some more digging and my Trans builder sent me to this company that's makes a 4 pulse square wave vss that screws onto the factory th400 mechanical vss, just like the MC piece for the r154. The only thing is, its a 2 wire sensor. Ground and output.

So I'm assuming I can take the 3 wire plug and use the ground and output pins and wire them into the new sensor. Than tape of the 3rd wire, which i believe would be the power wire. In theory, this should work?

Now for getting the correct MPH. The th400 uses plastic gears. One on the tail shaft (driven gear) and one the mechanical speedo (drive gear). To determine what gears you need. you will need to know the rear tire height and rear end gear ratio. You can email American Hot Rod Solutions and tell them these specs and they will tell you which gears you need. Does this sound plausible? I may just give it a try when my th400 actually comes in.

Speed sensor company. It is not listed on there site but they do carry the correct one.
http://www.jagsthatrun.com/Pages/Spe...eedometer.html

Ali SC3

iTrader: (10)

that sounds very plausible but guessing at the number of teeth would take a while. testing out a few would probably home in on the right one faster.

8052JZ

iTrader: (13)

Small update got all the speedo gears along with speedo cable to 4 pulse generator all installed on the Th400. I think I can give this a test buy clamping it down onto a hand held Drill to drive the shaft and see if the speedo will work. Going to try it out tonight.




Gear on the output shaft installed

speedo housing is in.

And the Converter screwed on

8052JZ

iTrader: (13)

Ran the test last night and to my skeptical amazement, it all works! This just might be a new method of getting the speedo to work with the th400 other than using the dikota digital box. This is a lot simpler than wiring in the box in my opinion and I'm very happy. BUT we have yet to test how accurate it will be. If the MPH is off all you have to do is swap out the plastic gears to more or less teeth to get the correct reading.

I temperarly connected the sensor to the excisting speed sensor plug. One wire to sensor ground and one wire to signal wire.




And here you can see my hand held drill hit 40mph at half throttle lol

Ali SC3

iTrader: (10)

good work and very impressive, had a feeling something would show up doing it that way. now just need to dial it in but you have all the hard stuff done
half throttle... lol

8052JZ

iTrader: (13)

Happy I did my homework and asked around. Diffidently paid off.

In the the next week or so I should have the th400 in the car and driving. I will post results on how accurate the MPH is.

8052JZ

iTrader: (13)

END result:

Everything is working as it should with this VSS adapter wired to the factory harness. Speed is dead on from the OEM Speedo VS a GPS. I think this is much easier to do than using a Dikota Digital box and hoping that it will work.

Cheers!