4WD Swap How To - Transfer Case VSS Speed Sensor Options

When swapping the PreRunner to 4WD, you know the Speed Sensor will need to be extended.
On the PreRunner, the speed sensor is in the tail section of the A340E. With the A340F, the speed sensor is located in the transfer case. I'm not going to go into detail on that but its a simple thing - snip the connector and extend it out by 6 inches or so. Suggest using 16 AWG GXL.

On older J shift transfer cases, the VSS is mechanical. The PreRunner uses an electronic speed sensor. To make this easy, Mechanical to Electronic adapters are sold. They are typically made of plastic and for the most part, cheaply made. As an example,

Low Range Offroad sells one such adapter for roughly $45 bucks.
https://lowrangeoffroad.com/speedometer-adapter-mechanical-to-electrical-vss.html




Marlin Crawler also offers up one they say is designed in-house and is a few dollars more - $49.00. With Marlin's adapter, the "pin" does not fall out when tipped at an angle (like the TrailGear adapter). Overall, it is a much better build.
https://www.marlincrawler.com/transfer-case/parts-upgrade/misc-hardware/vehicle-speed-sensor-mci

Marlin's adapter pictured with the mechanical sensor attached.


One problem exists with these plastic adapters, they're cheap. I had initially went with Low Range OR/Trail Gear's sensor when I swapped to 4WD. It was fine for a day and then suddenly my speedo just up and quit. Cross checked everything, wiring - all of it. Turned out the little pin that the mechanical gear attaches to in the housing of the speed sensor is a weak point. Whatever it plugs into on the adapter is made of plastic and can fail apparently.

I had ordered the Marlin Crawler adapter after reading positive results here on TW. It arrived and I swapped it in without issue and speed was again being reported.

One thing was still bugging me. These plastic adapters sit so close to the CAT, they're made of plastic and I know first hand that they can fail. I started thinking about other options and remembered a writeup that Dan (@turbodb) did on replacing his speedo gear - he was trying to correct MPH and compensating for aftermarket tire sizes. That sensor, it looked exactly like the mechanical sensor but had the same electrical connector as these adapters.

So why not swap over to the same sensor that is in the 1997-2012 4WD Taco? I looked it up. Part#8318112020. It is crazy expensive ($330 locally! $230 at partsdeal)! I turned to partsouq. I've ordered from them during the swap countless times and they are legit. Great prices and even though they're overseas, shipping is reasonable and lightning quick. They of course had it and their price - $129. So the way I see it, these plastic adapter cost nearly 50 bucks and fail. I had no issue with putting out the $129 and waiting a few days. Toyota quality and no more plastic.

One problem though... the speedo gear that is in the mechanical VSSs... it's too long for the electronic housing. It will need to be replaced. I looked it up and yep, you guessed it - partsouq had it for $13. Half of what PartsDeal had it listed for. I ordered the 30-tooth gear (Part# 3340339365) since I'm on 255/85/16s and 4.10. Speedo is still slightly off but I'll look at that again later.



Mechanical with Adapter on the left, Electronic on the right


The bolt that secures the VSS to the transfer case will also need to be replaced. The mechanical VSS bolt is too short. The correct bolt is Part# 9161160828. You can probably walk into Ace Hardware/Lowes/Home Depot and find an alternative but I just called up my local parts counter and had them order it. Will pick it up tomorrow.

The bolt for the transfer case's little skid also fits but is still a tad too short.

So there you go... Another alternative to working out the VSS on the 4WD swap.

Again, here are the parts you'll need.
SENSOR, SPEEDOMETER 8318112020 | Toyota Parts | PartSouq
GEAR SUB-ASSY, SPEEDOMETER DRIVEN (ATM) 3340339365 | Toyota Parts | PartSouq (There is a 31-tooth gear as well, see Dan's linked write up above for that info)
BOLT (FOR TRANSFER CASE) 9161160828 | Toyota Parts | PartSouq

NOTE: When installing, give the o-ring a slight coat of ATF and the bolt has a torque spec of 12 ft lbs.



EDIT: Zane @Speedytech7 mentioned the LandCruiser VSS would work as well. If you have easy access to one, give it a try. As Zane mentioned, Toyota has been using this forever so there are definitely multiple ways of doing this without the use of some plastic adapter

In fact, here is the list of the vehicles which use this speed sensor.



Next Step - Wire up your 4WD indicator light on the instrument cluster
https://www.tacomaworld.com/threads...dicator-light-and-a-t-p-neutral-light.783875/

 

Thank You Sir!

 

Another great reference for the 4x4 swap archive. Strong work!

 

Thank you for the write up on this!

So I just picked up a 98 4Runner J shift case for my 2003 prerunner conversion, and given the 4Runner seemingly got their speed reading from ABS, there is a plug over the normal VSS port on the t case. Looking inside, I can see the worm gear on the shaft inside the case, so I'm assuming this write up will still work for what I need even though there was never a sensor in that particular port. Regarding the 30-tooth gear you went with (Part# 3340339365), was there any rhyme or reason you chose that one for your setup? I'm just running stock size 265/70R16 with 4.10 gears so curious if that one would also apply for me.

 

When I was doing my research here on the forum and after reading @turbodb posts (https://adventuretaco.com/replacing-the-speedo-gear/) on his speedo gear swaps, I think I just stuck with what he went with since we were both on the same tire size/gear ratio (at the time of course).


Can you take a pic of that 'plug' where the VSS should be?

 

Ok cool that makes sense, thanks for linking that! I suppose the obvious thing I can do here is pop my current speedo out of my tail housing and see what's going on there if there's anything to learn.

And yes, attached a couple of pics showing what I was referring to!

 

If you pull yours, I'm nearly positive the difference is going to be the diameter of the gear. The A340E is smaller than the 340F. I could be wrong though. I used a transfer case from a 95 taco so I didn't run into the issue with a plug. @Cattywampus might be able to shed some light on the whole plug thing.

 

Yep that makes sense, I also just looked up the part number for the A340E and the gear is clearly much smaller in diameter than the one you got (which makes sense given it's receiving the speed rating from a different worm drive in the tail housing vs. transfer vase as you mentioned), but what I also did was cross check the stock part number for the 4x4 version of my truck and it gave me the exact 30 tooth gear you had listed, so I think it's safe to assume that is the correct one for me too. It does look like the 4Runner case will simply just accept the sensor into the existing plug slot, but @Cattywampus if you have any insight lmk!