Maiden Voyage / Speedo Error

[Merle Coggins]

What a fun morning. I cleared some things out of the way in the shop and drove the truck out into the sunlite for the first time since the final assembly and painting of the front. After a couple of loops around the yard, I headed off to the corner gas station to add a bit of go juice. Bad news here, the gas gauge isn't working, even with the new sender.

Other than a stumble upon acceleration (accelerator pump needs work) it ran great and drove down the road nicely. However, I noticed that the speedo seemed to be reading quite high. When I got back to the shop I took the GPS out of my other truck and went for another drive. When the GPS is indicating 55 MPH, the speedo is indicating 70 MPH. Up to around 25 - 30 MPH it is fairly close. Then it really starts to climb. Does it just need lube? Or is something else wrong with it. Could it be off because I had the needle and face off to have it redone?

Beside the couple of glitches, it was a fun ride. I've been waiting for that for over 2 years now.

Now I have more room to work on the bed panels. 4 more weeks until the WPC meet in PA. I hope I can make it.

Merle

[wallytoo]

bet that was a satisfying ride, merle. great.

sometimes, the gps units read a little slow, too, so if the speedo reads a little high, you could end up with a sizeable gap, especially at higher speeds (where i've found more error with gps units).

it probably wouldn't hurt to lubricate the unit, though.

wally

[TodFitch]

With the selective availability turned off by the military and the fact that almost all recent GPS units have multiple receivers, the GPS should be pretty accurate as long as it has a reasonably good view of the sky.

Speedometers reading high are usually due to a change in gear ratios somewhere. How about the odometer? Is it accurate or not? If there was a gear change (rear end/tire size/speedometer take off gear) then both the speedometer and odometer should be off by the same amount.

If the odometer is correct then you likely have a weak return spring on the speedometer needle. Not much else to go wrong with them that would make them read high. (More things for reading low. . .)

[wallytoo]

With the selective availability turned off by the military and the fact that almost all recent GPS units have multiple receivers, the GPS should be pretty accurate as long as it has a reasonably good view of the sky.

+/- 18 feet is what i usually get, generally with at least 10 sats. locked in. still, with the constantly changing 3D position of a vehicle moving at 60 mph, there's going to be inaccuracy, selective avail. or not. nevermind that a pilothouse cab does NOT offer a 360 degree "view" for the receiver. my experience has shown that they (gps units) list a speed that is slower than actual speed. yrmv.

[Byronb3b]

Congrats Merle, I just knew you could do it, hope to see you in pa. Byron

[Merle Coggins]

Thanks, Tod, for reminding me to check the Odometer. I should have thought of that too. I expect it to be off some though. I have changed diff gears from 4.10's to 3.73's (Thanks Normspeed, they work great). But that gear change should have made it read slow, not fast. I'll double check the Odometer. Is there any way to add tension to the spring in the speedo to make it more accurate?

Wally,

I feel pretty comfortable with the accuracy of the speed reading on my GPS. I've checked it against highway mile markers when I was calibrating the speedo on my motorcycle. (For the bike I used a "Yellow Box" electronic recalibrator, since it is electronic.) The GPS does read slightly slower than the speedo in my company truck, but it's also quite common for speedos to read slightly high. I've never seen a vehicle with a perfectly accurate speedo.

Norm,

I have a ground wire attached to the sender going a the trans cover bolt. Since the battery Pos. cable is also attached to a trans cover bolt it should be grounding the sender pretty well. It's a new sender from Robert's. I'll just have to get in and double check my wiring and the gauge.

Byron,

I'll be in PA, with or without the truck. But hopefully with, even if I have to trailer it out there. See ya there.

Merle

[Merle Coggins]

Well, I compared the odo with my GPS. 5.0 miles registered on the odometer = 5.2 miles on the GPS. Actually not too bad considering the gear change from 4.10 to 3.73. By my calculations it's off about 4%.

During that test the speedo wasn't too far off. It was actually farily accurate until I got over 50, then it climbed fast. Then this morning, on my way into work, it was pegging the gauge at around 45. Is it temperature related, or does it just need a good cleaning and lube?

Merle

[woodscavenger]

Maybe it just needs coffee!

My truck has the same 3.73. How does yours feel at 50mph? Does it have much more to give?

Can I get and aftermarket speedo for mine since my truck came without any guages?

[Merle Coggins]

At 55 it actually felt comfortable. I haven't pushed it up past that yet, but it felt as though I could without difficulty.

Also, this morning I had the windows up while I drove it, and I noticed a whirring noise that I didn't hear before. (I always had the windows down before) I'm thinking it's noise from the speedo cable or from the speedo itself. What type of lube should I use for each?

Merle

[MBF]

Merle-I've pulled the core out of the housing and used both Vaseline or a graphite liquid with good results, but I think first you should wipe down the inner cable and then maybe flush some penetrant through the outer jacket, and then chase that with some compressed air. There is also a screw type fitting that holds an oiled wick on the back of the speedo-I'd hit that with a little light oil too. Mike

[greg g]

Merle, tell us about the Chrysler affair in PA, Where and when??? Are you talking about Chryslers at Carlisle??

[46mopar.]

That first couple of rides are always the best. Congrats

Now lets see that tire smoking burn-out picture oh I forgot where I was for a second.

[Merle Coggins]

Greg,

I'm refering to the WPC Club national meet in Farmington, PA the week of July 13th - 17th.

See http://www.chryslerclub.org/Annual_Meet_2008.html

[Bouncy B]

Because my speedo isn't hooked up yet, I used WPS on my first run. WPS is Wife Positioning System. She was positioned in the car behind me and we were on our cell phones. Works on cloudy days as well.