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+--- Thread: Speedometer Conversion (/showthread.php?tid=1529)
Speedometer Conversion - DrewGerhan - 07-26-2010
I just recently swapped a manual transmission into my 300SD and am putting the finishing touches on the swap. My question is, does anyone know of a way to adapt the stock electrical speedometer to the mechanical manual transmission?
Are the tailshafts swapable between the old auto and new manual trans or would some magnets and a magnetic pick up on the driveshaft work better?
RE: Speedometer Conversion - aaa - 07-26-2010
I doubt the tailshafts are swappable. The stock electric setup appears to be picking up 4 pulses or whatever per rotation, from the appearance of the speedo "gear" inside.
RE: Speedometer Conversion - GREASY_BEAST - 07-26-2010
(07-26-2010, 07:59 PM)aaa I doubt the tailshafts are swappable. The stock electric setup appears to be picking up 4 pulses or whatever per rotation, from the appearance of the speedo "gear" inside.
You could probably just use a hall effect sensor and position it so the balancing weights or the flex disc bolts or some such thing actuate it. In any case, unless it has the same properties as the stock electronic speedo pickup, you will need some sort of circuitry to convert the signal...
RE: Speedometer Conversion - SurfRodder - 07-26-2010
yes, you can swap the tailshafts... I pulled an auto out of a 300SD and swapped the tailshafts to make it work in my 300D...so you should be able to do the same/opposite.
you need a special socket to get the nut off the yoke though, Snapon sells them, its a 30mm deep 12pt socket, might be able to procure it elsewhere tho.
if you were closer, I'd let you borrow mine.
RE: Speedometer Conversion - willbhere4u - 07-26-2010
can you really swap tail shafts from auto to manual? witch trans did you put in 4spd?
RE: Speedometer Conversion - SurfRodder - 07-27-2010
totally missed the manual part.... thought he was replacing an auto with the opposite one... I dont think it can be done either, but prove me wrong!
RE: Speedometer Conversion - ForcedInduction - 07-27-2010
Find the tailhousing from a 280SE with a manual, they're out there. Probably makes a 5-speed 300D look common though.
The world EPC probably has the part number and year range.
RE: Speedometer Conversion - JB3 - 07-27-2010
(07-26-2010, 07:59 PM)aaa I doubt the tailshafts are swappable. The stock electric setup appears to be picking up 4 pulses or whatever per rotation, from the appearance of the speedo "gear" inside.
x2. Can you put the mechanical speedo in the 300SD? Might be easier to adapt a mechanical speedo out of a 300D if possible instead of trying to create and convert a signal to work with the SD stock speedo.
RE: Speedometer Conversion - Biohazard - 07-27-2010
(07-27-2010, 06:58 AM)dropnosky(07-26-2010, 07:59 PM)aaa I doubt the tailshafts are swappable. The stock electric setup appears to be picking up 4 pulses or whatever per rotation, from the appearance of the speedo "gear" inside.
x2. Can you put the mechanical speedo in the 300SD? Might be easier to adapt a mechanical speedo out of a 300D if possible instead of trying to create and convert a signal to work with the SD stock speedo.
I have a speedo from a W116, it's mechanical. I agree with Dropnosky, it may be easier to adapt a mechanical speedo with a cable than try to adapt a different tailshaft housing. Plus, with swapping to a mechanical speedo, you can change the ratio with an inline adapter for much cheaper.
RE: Speedometer Conversion - DeliveryValve - 07-27-2010
There is a guy in PeachParts who had stated his mechanic weld supposedly welded on some magnets to the driveshaft and used a modified pickup from the SD autotrans. He says it works beautifully. I've asked him for some pics in the past, but never got a response.
I think this is the way to go for the w126.
.
RE: Speedometer Conversion - willbhere4u - 07-27-2010
I've seen magnets electrical taped on to a drive shaft for just this purpose
I would not recommend doing it that way permanently!
I would think the magnets out of a couple sets of headphone would work! As I remember they are rare earth magnets???
RE: Speedometer Conversion - DrewGerhan - 07-27-2010
I was planning on dealing with it either later today or tomorrow. I guess my plan will be to take apart the tailshaft on the auto first and see what the workings of the speed sensor are like and go from there.
RE: Speedometer Conversion - ForcedInduction - 07-28-2010
The problem with adding magnets is that will significantly impact driveshaft balance and pick up road debris over time.
Quote:I guess my plan will be to take apart the tailshaft on the auto first and see what the workings of the speed sensor are like and go from there.
This is the difference for the auto, the tailhousings are interchangeable.
You could put the tone ring in place of the worm drive, cut and weld the cable portion out and weld a bung in place for the electric pickup.
RE: Speedometer Conversion - DrewGerhan - 07-29-2010
I assume the rotating pieces (from the first picture) are the same physical size and spline size?
RE: Speedometer Conversion - ForcedInduction - 07-30-2010
Yes. Its just the perspective of the picture that makes them look different.
RE: Speedometer Conversion - DrewGerhan - 07-30-2010
Got into both transmissions tonight. Nothing is similar between the two. My next plan is either to buy a gps and call it done or to get a speedo and cable that is from a 240 or 300D.
RE: Speedometer Conversion - willbhere4u - 07-30-2010
or w116