bmwe21.net forums

Hi all,
I'm stuck in a hotel down in Southampton due to work & have spent the last hour reading various build threads. In a few of them they state that once they'd fitted new gearboxes that the speedo no longer worked but they could get spoked readings through satnav.
Does the speedo need to work for the car to obtain an MOT?
I'm still searching & saving for my next E21 but a lot of them seem to be automatic for sale at the moment. So for converting to manual could I use an E30 gearbox & use my TomTom to get speed readings?

My understanding is that satellite based speedo systems are not allowed for MOT.

That was my thought but how did these others get an MOT without a functioning speedo???

It is illegal to drive a vehicle on a public road without a correctly functioning speedometer.

However, speedometer function is not checked as a part of the M.O.T. test, so you can't fail an M.O.T. for it.

instead of trying to cheap out why don't you save a bit more and do the manual conversion properly - it'd probably cost you £100 extra.

I'm not trying to cheap out Nas I'm just considering options, I'm still thinking about an M42 conversion instead of the M52 and as the gearbox that comes with the M42 doesn't have a mechanical speedo pick up on it then just wondered which way to go... Just been looking at the Stack ST700 dash gauge with integrated speed & rev counter, it's electrical so should work with the Getrag box out of the 318ti & won't look out of place in the E21.
But to start with I could get the engine & box in, running & use the satnav while I sort through teething problems.

ah sorry my post may have came over as harsh, what I meant that if you spent a bit more it would save you some headaches.

The newer boxes don't have a speedo sender... The newer bmws pick up speed from the sensor in the diff. So I used a GPS speedo sender. I got mine from Dakota digital its called the 50-1 but its pretty expensive there are now cheaper alternatives. You can use the stack dash but you still need a GPS sender to send the signals to the dash. .

It's ok Nas, I know what you meant.
It looks like in the long run I'd be best off looking for a decent E21 M10 5spd & using that. It should hold up with 170-190bhp shouldn't it?
They're just so hard to find

the m10 box wont mate to the m42, you need the m20 box

There's a guide in the tech section about swapping the bell housings over on the 245 gearboxes (M10 to M40/42) and it states that the gearboxes are the same just with different bell housings.

http://www.bmwe21.net/forum/viewtopic.php?f=61&t=19851

This is the thread I'm talking about Nas.

oh yeah forgot about that

I'm intending to use a speedo sensor that will pick up pulses from the prop shaft or whatever. I'll still need to change the speedo head tho

What engine & box are you using healeyneil?

Mines running an E24 electric speedo in the binnicle with an E30 diff sensor mounted near the driveshaft. I got a 9 tooth chopper wheer laser cut to fit the cv joint bolt pattern.

Just need a live and earth to the speedo
One signal wire to the sensor and one earth wire on the sensor.

Calibration is a bit out. Shows 77mph at 70mph from the satnav.

Mileage over my europe trip was:

Actual mileage - 2395 miles
recorded mileage - 2552 miles

so just 6.55% error, where the regulations are 10% overread for accuracy.

This is running 205/60/15 tyres. It would be more accurate with larger diameter similar to teh E24.

Regards

Ben

Pic of the speedo in the dash:



Ben