Yes, the Marlin Crawler VSS adaptor is needed for an MKIII Supra R154 or an MKIII Supra W58 since both of those use a mechanical cable drive for the speedometer. The Marlin VSS adaptor just screws into place and accepts the SC300's VSS connector.

However, be aware that MKIII Supra W58's are slightly weaker than SC300/MKIV Supra W58's. I'd recommend the latter versions. R154's are a different story.

Yes, if you want to have your speedometer read correctly you'll need either a Yellr YellowBox V4 with their SC/MKIV style harness cable... or you can also get a similar product from Dakota Digital (not sure if they also sell a premade harness for SC/MKIV's). Personally I recommend the Yellowbox.

Also note that any W58 from an SC300 will be calibrated for a 4.083 ratio while a 93.5-96 Supra W58 will be calibrated for a 4.272 ratio (same as your automatic SC). 97 Supra W58's are calibrated for 4.083 ratios.

 

I currently have a 97 sc 300 with R154 swap (was an auto). The motor is still stock but i just changed the auto differential to the sc 430 3.26 gear ratio. Is the yellr yellowbox v4 a good choice to correct my speedometer?

 

Yes the Yellr Yellowbox V4 is an excellent choice to correct your speedometer inaccuracy. When ordering from their website you will be able to specify whether or not you want a Plug-and-Play harness to go with it which I do recommend.

Yellr makes a plug and play harness for the 92-00 SC300/400 and 93-98 Supra MKIV (manual transmission applications using the common W-series, R-series and V-series 3-wire VSS signal). You must specify in the Yellowbox order page the MAKE, MODEL, MODEL YEAR and TRANSMISSION TYPE under the correct harness heading (you will want "PnP harness").

I run one of these myself with a converted MKIII Supra R154. It will be the same for all R154's. Look here for DIY installation instructions for the Yellowbox V4 in your SC with the optional PnP harness. Start from Page 8, Post #123 through Post #130 on that page.

Note the instructions I've outlined for routing the V4 controller cable into the transmission tunnel's interior opening by way of the unused RHD parking brake mounting holes in your trans tunnel. Very convenient. It requires noting the wire locations on the Yellowbox Molex connector, temporarily de-pinning that connector, routing the wires with lead ends through one of the trans tunnel RHD parking brake holes (or the opposite LHD unused holes if anyone reading this uses a V4 on a RHD Soarer), and re-pinning the connector. Just make sure that the control cable goes over the transmission and doesn't have much slack. You don't want to strain the VSS connector wires on the transmission but you also don't want the long part of the V4 harness line to droop onto your driveshaft or transmission tail housing.

https://www.clublexus.com/forums/per...et-swap-9.html

Calibration is very easy with dip switches. Use the calculators in the thread to guesstimate your correction percentage based on your transmission gears and final drive ratio. You will want the numbers on the dial to very closely match what a portable GPS is telling your your car's actual speed is. It takes a little finesse.

Note: You MUST turn the car's ignition off before initiating each calibration change to the Yellow Box. It doesn't know how to understand dip switch changes on the fly while the electrical system is on. It should not take many tries to get it spot on at all speeds 1st-5th.

 

Thanks Kahn for the info man. Im gonna order it pretty soon. I checked out the site and i think there's a v5 version now. Been doing alot of reading on 1jzgte non vvti swaps (gonna try and do the wire harness myself) and i somehow ended up on that post so i popped the question. My speedometer is way off especially in 5th at about 60 im really doing 80 and in lower gears 30 is 40. Thanks again for the info i really appreciate it.

 

No problem! Good luck!

I was not aware that a V5 version had been released. I don't know whether it's a shoo-in update that is compatible or not. Best to email Yellr and ask them. Also, ask if the V5 is compatible with the 93-98 Supra & 92-97 SC300 PnP harness that was tested on the V4 versions.