Angle drive shaft appears to be too long

[Shep]

No just don't run Drills AT ALL! Drills are not a suitable diagnostic tool. Please don't make my mistake, I have learned this from experience the hard way. Here's why:

Drills have next to zero inertia nor momentum compared to a DeLorean at speed, the speedo has been designed to work around the stopping forces of a two thousand pound vehicle, not a ten pound rotary device. 88 MPH to zero in a second and a half -- I don't even know if a Bugatti Veyron is capable of that kind of speed changing. It's certainly not designed to. There is no amount of carefulness in the world that can overcome the problem a drill imposes.

If you absolutely must diagnose issues, leave everything connected and dyno the left front wheel. Use the dyno to change speeds, that's what it's there for (by the way, these are the same powered dynos that often are used by shops to diagnose wheel balancing issues to, so they're out there).

[Josh]

No just don't run Drills AT ALL! Drills are not a suitable diagnostic tool. Please don't make my mistake, I have learned this from experience the hard way. Here's why:

Drills have next to zero inertia nor momentum compared to a DeLorean at speed, the speedo has been designed to work around the stopping forces of a two thousand pound vehicle, not a ten pound rotary device. 88 MPH to zero in a second and a half -- I don't even know if a Bugatti Veyron is capable of that kind of speed changing. It's certainly not designed to. There is no amount of carefulness in the world that can overcome the problem a drill imposes.

If you absolutely must diagnose issues, leave everything connected and dyno the left front wheel. Use the dyno to change speeds, that's what it's there for (by the way, these are the same powered dynos that often are used by shops to diagnose wheel balancing issues to, so they're out there).

20729092_1785947904752048_6462161560983490284_o.jpg

My speedometer still functions fine, and I have done this a handful of times.

[Shep]

Which is effectively dynoing the left front wheel -- the brake caliper provides the inertia necessary to avoid damage to the speedometer.

That is the correct way to do what I say is wrong in a manner that is right also

(If that's confusing, drill on bare speedo cables will cause damage. Drill on wheel or brake rotor is basically a makeshift dyno and won't hurt at all)

[Nicholas R]

What? I'm not sure I understand what inertia has to do with the speedometer functionality. As far as I know, rotating the cable just creates a magnetic field that moves the needle. The torque on the speedo cable is irrelevant; all that matters is the speed of rotation.

[David T]

Yes, the speedometer only measures the rotational speed of the cable. 1,000 RPM's = 60 MPH.

[iflights]

Calling Bill Richardson...watched your video on Farrar's angle drive. Exactly how long is the shaft from end to end that you fashioned?

[iflights]

Calling Bill Richardson...watched your video on Farrar's angle drive. Exactly how long is the shaft from end to end that you fashioned?

My mistake, Bill Robertson. Bill Richardson is my neighbor, and he doesn't own a DeLorean.

[Nicholas R]

Which is effectively dynoing the left front wheel -- the brake caliper provides the inertia necessary to avoid damage to the speedometer.

That is the correct way to do what I say is wrong in a manner that is right also

(If that's confusing, drill on bare speedo cables will cause damage. Drill on wheel or brake rotor is basically a makeshift dyno and won't hurt at all)

Just a point of note, the photo shown doesn't show the drill turning the brake rotor; it shows the drill connected directly to the angle drive shaft. The only way to spin the angle drive via the brake rotor is if you rotate the rotor by hand, and have the angle drive cap in place (thereby linking the rotor and angle drive).

[Shep]

Exactly how long is the shaft from end to end that you fashioned?

Lay out old next to new, leave Lambda counter connected, use the total as reference. If it fits now, match it. Simple

What? I'm not sure I understand what inertia has to do with the speedometer functionality. As far as I know, rotating the cable just creates a magnetic field that moves the needle. The torque on the speedo cable is irrelevant; all that matters is the speed of rotation.

Okay, I'm learning a bit as I go here, this was my understanding, correct any mistakes:

In the scenario where you take the end of a speedo cable, which is connected to a speedo, and attach it directly to the drill like this:

Drill --> Cable --> Speedo

With nothing in between, it's not hard at all to simply pull the drill to full speed immediately and have the speedo jump from 0 to 100 MPH in a quarter of a second. It's this very action I am cautioning against. A brake rotor or some other type of flywheel will slow the acceleration enough to not to not be an issue. As far as what those issues, are, well, this was how it was explained to me:

There is a peg on the speedo that prevents the needle moving past about 90 MPH stock. If the needle is forced against this quickly, it can become offset, so everything reads a certain amount "off". I want to say this one corrects, I don't have a speedo handy to look at currently, but I believe there was a peg on the backside that cuts off at 0 MPH to prevent reversing from showing on the speedo. Which honestly was another angle I couldn't figure out as the same guy said reversing lowers your mileage. He really knows his stuff, but this sounded a bit to me.

The second part is that it "wears out" quicker. Given that it's a magnetometer, I would assume that means it demagnetizes itself, I thought it was some kind of gearing and it added "tooth play" when I addressed this earlier (which, by the way, is the problem angle drives tend to have. Tooth play + time = failure).

The other components however are still prone to failure. The cables can unwind, the lambda counter can snap, but generally they don't do much more than add a little bit of flex into a system that could use a slight bit more anyways. Downstream of the angle drive, of course, there's really no easy way to replace it and bypass all the shenanigans. Some guys have, but again, no "easy" way exists.

Just a point of note, the photo shown doesn't show the drill turning the brake rotor; it shows the drill connected directly to the angle drive shaft. The only way to spin the angle drive via the brake rotor is if you rotate the rotor by hand, and have the angle drive cap in place (thereby linking the rotor and angle drive).

Oh god good catch, yeah I need to redact that earlier statement that using a drill as pictured was correct, that will prematurely kill the angle drive if it wasn't dead already. Baby steps on that spot, the gears in the angle drives are hypersensitive!!! Slow and steady wins the race, don't overdo it!

[Nicholas R]

There is a peg on the speedo that prevents the needle moving past about 90 MPH stock. If the needle is forced against this quickly, it can become offset, so everything reads a certain amount "off". I want to say this one corrects, I don't have a speedo handy to look at currently, but I believe there was a peg on the backside that cuts off at 0 MPH to prevent reversing from showing on the speedo. Which honestly was another angle I couldn't figure out as the same guy said reversing lowers your mileage. He really knows his stuff, but this sounded a bit to me.

When you replace the trip reset shaft, I believe one of the steps is to remove the needle from the center stud. I remember doing this when I installed my 140mph speedo. It's definitely important that the needle goes back at the right angle otherwise you will indeed always read incorrectly. I'm not sure if driving the needle into the stop while driving could cause it to slip, but I suppose if you were to rotate the speedo cable at the equivalent speed of say, 200mph on an 85mph speedometer, you could feasibly create enough torque on the shaft to slip the needle; especially if the needle was slightly loose on the shaft to begin with.