Autometer Speedometer Issue

[bigal0043]

I’ve been fine-tuning my Cobra now that spring is here, sorting out minor bugs and tweaks. One frustrating issue I’ve noticed is with my speedometer. I managed to calibrate it, but when I'm under 20 MPH, the gauge goes haywire—jumping between 0 and 60, sometimes holding at 60 before suddenly dropping back to 0. Once I hit 20 MPH or higher, it functions correctly again. Any ideas on what could be causing this?

[michael everson]

Is it electric and using the counter on the tail shaft of the transmission? If so pull that out and have a look at it. Maybe its defective or gear is damaged.
Mike

[bigal0043]

I’m sorry I forgot to add that part, it’s a T5 with the plastic gear. Didn’t even think to pull that and check it, only have around 180 miles thus far.

[Blitzboy54]

Once you pull it you can spin the sender with a drill. If the speedo works normally it’s probably the gear in the tail shaft. If it’s still acting the way it is I would assume it’s the sender or the gauge. Sender is a cheep part. I have a couple spares your welcome to one of them. Test a new sender. If that doesn’t do it it’s likely the gauge is bad or you have some sort of funky wiring but I don’t see how that could be speed dependent.

[Malibu46pt]

I had the same issue. I contacted Speed Hut and they sent me a filter that goes in line with speedometer. Problem solved.

[bigal0043]

I had the same issue. I contacted Speed Hut and they sent me a filter that goes in line with speedometer. Problem solved.

Interesting, any idea what the part number was or what exactly they sent you?

[Malibu46pt]

I do not recall. I just called them and explained the issue. They were well aware of the problem and sent me the filter at no charge.

[bigal0043]

I contacted auto meter, they brought up an interesting question/thought. What sensor gear did I put in. I guess if it’s not sized correctly it will work at higher speeds but won’t generate voltage correctly at low speeds.

Looking at my packing lists. I just used what came in the kit which was a 3.73 gear and if I remember correctly I have a 2.73 (on my winter list to change to 4.55). Going to order a much lower tooth count speed gear.

[phileas_fogg]

Interesting. When I built my car 10 years ago, I called Speed Hut to find out of the gear in my sensor matched my differential. They said the gear didn't matter, because the gauge calibration could accommodate whatever gear was in the sensor.


John

EDIT: Somehow I missed that you're using an Autometer gauge (even though it's right there in the subject!), so my Speedhut anecdote isn't particularly helpful with your problem. But perhaps a Speedhut guy will find this information useful.

[Dgc333]

FWIW, I have Autometer speedos in both my 33 hot rod and my 68 Barracuda. Over the 2 mile calibration loop my hot rod counts somewhat over 12000 pulses, the Barracuda on the same loop counts around 6700 pulses. The speedos both work fine reading about 1 mph low below 45 miles per hour and up at 60 miles per hour they read about 1 mph high when compared to a GPS speedo in my phone. The hot rod has a T5 with a new replacement sensor and what ever gear Ford supplied in a 92 Mustang. The Barracuda is using an Autometer sensor that screws onto the speedo cable connection on the tranny. The gear is the best fit Mopar has for a 3.55 gear with 28" tall tires, it was always read about 4 mph low.

[bigal0043]

Updated - swapped to a white gear I think it was 17 tooth, redid the calibration and works perfect now. I'll keep the one that came with the kit for when i swap the rear end gears out over winter.