Speedometer way off....

[knac1234]

All,

Drove the SIII to work today.....nice to have it back in regular use!

As always happens, I have a few odds and ends to finish, and noticed a few things also.

So, prior to the work I did, the speedo needle flew all around the gauge, making accurate speed reading impossible. During the work I did, I replaced the speedo cable, thinking it might be bad (turns out it was held in with only 2 of 3 screws also). Anyway, the speedo now works, and the needle holds nice and steady as it should.

However, when using my GPS, it is clear that, as my speed increases, the speedo is WAY off. Up to about 25mph it is pretty accurate, but at "60mph," per the GPS I am doing 40.....at "80 mph" I am doing 55-60.

Do you think this is a result of the tires I have on it (same size as what was on there, but probably not "stock"....30X9.5X15) or something else?

Not overly concerned, as I am leaving my GPS on the dash unless I need it in another car. Not like I will get a speeding ticket based upon the speedo either

Julian

[Terrys]

That great an error isn't likely the tires. My guess is that your speedo's magnet is loosing magnetism. That said I never saw an accurate land rover speedo. Then again, maybe you warped into another dimension, to get your GPS to actually believe you were doing 80.

[knac1234]

Terry,

I am used to seeing in all my old Brit cars some deviation from reality on speed, but this is pretty massive! Will be using the GPS as my guide on speed!

Julian

[siii8873]

sorry slight hijack,
this AM it was cold and I started down the interstate. I was on a flat stretch and was trying to get my truck up to usual flat cruising speed of about 48-50 (no OD). My speedo was reading ~35 and the engine sounded like it was working real hard. I thought I had a problem until I was passed by a car that didn't fly by me. Then I realized that it was the speedo reading low and must have been pushing 60+ in hindsight from sound, ect. Never happened before. BTW for the remainder of the trip drove truck by sound which works great.

[Terrys]

The speedo in my 110 reads a consistant 10% higher than what I'm travelling at, according to the GPS. I don't worry about tickets only because 72ish sounds like 120 anyway. The cold related problem I have is that it howls until the cabin begins to warm up. (a relative term in a Landy of any generation)

[Jeff Aronson]

You might find that your speedometer cable is slipping under higher wheel speeds; check to be certain it is tight at the transmission end. Otherwise, I think you might have the same problem I did of the internal mechanisms requiring refurbishment.

One hint might be that if your odometer readings are generally accurate, but your speedometer reading is off, you would know the cable is turning correctly.

I sent my speedometer to Rovers North, who sent it off to a specialist and it came back working just fine.

Jeff

[knac1234]

Jeff,

Thanks. Yes, the cable is in the tranny end tight. I know this as, again, the old one I found to be held in with 2 screws barely. When replacing it, it was a bit of a fiddly nightmare. With the overdrive in the way, trying to tighten those screws with no room was tough, but they are tight.

Also, I think you are right on a rebuild. My "commute" is only about 10 miles.....which is about exactly what the odometer tracked going home yesterday.

Regards,
Julian

[Terrys]

Julian, As you know, the speed indicating portion of the unit is free to move, and is essentially dragged up by a magnet attached to the rear spinning disc. If the needle shaft is gummed up with any old lubricant, that will act as a friction brake and hold the needle shaft back. A drop of lighter fluid through the bushing, and the rear jewel will help disolve the old lube, then a drop of sewing machine oil, and you will find it may well indicate much more closely to the real speed.

[disco2hse]

If the difference increases with speed, then it is the gearing that is wrong. Do you have the right speedo/gearbox linkage for the vehicle?

[Terrys]

If the difference increases with speed, then it is the gearing that is wrong. Do you have the right speedo/gearbox linkage for the vehicle?

He's reading low, but the odometer is right on, so it's not the gearing.

[ThorH]

After re-reading his OP, it sounds like the speedo is reading high. (don't know if it makes a difference)

[knac1234]

Thanks for the input all!

To clarify:

-The odometer seems to be dead on
-The speedometer reads higher than actual speed (example: speedometer reads 80 mph, GPS states I am doing 55-60 mph)

Terry, if you still think that the oil/lighter fluid idea will work, let me know. I will give it a shot at some point. It's not too critical right now, as my portable GPS unit that usually sits in a drawer at home now has a new home in the center of the dash

Julian

[Terrys]

but at "60mph," per the GPS I am doing 40.....at "80 mph" I am doing 55-60.

I gotta stop reading these threads without my glasses.......... that little comma after the 60mph was hiding, but makes all the difference.
You can do the lube, it won't hurt, but the the issue now is the helical spring is shot. Actually it was your issue all along, "now" that I can read the OP.