SPF Speedo Error Fix

Lynn Miner · 10-14-07, 09:23 PM

FYI - Dennis Olthoff now has a fix for the SPF GT40 speedo error. The error is caused by the fact that the RBT/ZF does not have the proper drive gear and to date, Mr. Butafoy has been unable or unwilling to deal with that. Be that as it may be, Olthoff has built a gear reduction unit that mounts on the trans and the cable connects to it. No need for any other mods. DO claims .01% accuracy. Cost is $95. For those of you that may not be aware, the RBT/ZF trans causes the speedo to read about 22 mph high.

kgschrader · 10-15-07, 02:48 PM

Dennis says he's shipped my adapter, but I've not seen it yet.

And yes, with my 4:22 gears, it does read way high.

FWIW,
Kirby

Kim Petersen · 10-15-07, 10:13 PM

I wonder if the new ZFQ by Quaife is going to be calibrated to the SPF GT40 right out of the box? This is the tranny that many of us are waiting for in the hopes of completing cars that are otherwise done.

Lynn Miner · 10-15-07, 10:25 PM

Can't say Kim. Your best bet is to contact Chris Melia and ask him. Supposedly RBT is going to fix the problem in future units but when that will happen is anyone's guess. Considering all the other headaches associated with getting an RBT box in hand, I doubt that speedo error is high on their list if things to do.

Ron Earp · 10-15-07, 11:11 PM

There are boxes that correct this type of error available from commercial outlets.

Pegasus sells them as well as other places. You need to know the basics - tire size, gear ratios, teeth on speedo, speedo reduction/overdrive, as well as input/output type. Although it seems like a lot of choices and issues to go through there are not that many options with respect to cables/drives/reductions.