Speedo question/problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

glock35ipsc · 11-17-2004, 10:21 AM

I have been driving my 70 4x4 this week. Been doing alot of work to her to get her ready for my wife to drive to work when the weather turns bad.

I noticed that the spedo is off exactly 5mph compared to my GPS. Nothing surprising there. But I have noticed that every once in awhile, it will just drop about 5mph, then go back up. The needle doesn't really bounce, just out of the blue it will drop for 5 seconds to a minute, then pop back up.

I am sure the 5mph off thing is in the calibration, but is the up and down thing a bad speedo? The odometer quit working years and years ago, so I wouldn't feel bad about throwing another one in there.

Thanks for any suggestions. Also, anyone know the weight of a complete disc brake front crossmember?

JimKshortstep4x4 · 11-17-2004, 10:32 AM

Sounds like the speedo is bad. I would try replacing it first. If it were a cable or gear problem the needle would bounce.

Jim

Project1970 · 11-17-2004, 10:42 AM

5mph off at ALL speeds? That's not a calibration error (or at least, not as far as speedo gears in the transmission are concerned). The gap should widen as speeds increase.

glock35ipsc · 11-17-2004, 10:47 AM

Yeah, it is off by 5 at all speeds. If it says 25 the GPS says 30, if it says 55, the GPS says 60. The GPS is dead-nuts on compared to the speedo in my 03' Silverado, so I trust it. I have an extra speedo in the attic, I guess I'll put it in this weekend and see what happens.

Thanks guys!

68w/sbc406 · 11-17-2004, 12:02 PM

the speedo should be off by a % not a constant 5. as for the complete crossmember thing, they are heavy. it was all me and a friend could do to get it off of the ground to put it on jack stands

ale8oneboy · 11-17-2004, 12:24 PM

Would a different tire size affect this?

Fred T · 11-17-2004, 12:27 PM

It could be a zero error. The odometer issue is probably a plastic shaft inside the housing. I just had my speedo gone through at Bowtie Bits. Cleaned, calibrated, replaced the odometer shaft and painted the needle for $45. He has the work done in his shop.

68w/sbc406 · 11-17-2004, 12:43 PM

Quote:

Originally Posted by ale8oneboy

Would a different tire size affect this?

tire size, and gearing can effect this.

glock35ipsc · 11-17-2004, 12:48 PM

The truck has stock heigth tires and original gears. I think I will replace it with another speedo I have and go from there. I am not too concerned about fixing this one since the odometer quite working about 40,000 miles ago

Thanks all!

Project1970 · 11-17-2004, 01:23 PM

So does it actually read zero when stopped? It sounds like it should read 5mph then.

Yeah, the gauge itself is most likely broken.

glock35ipsc · 11-17-2004, 02:21 PM

Yup, it reads zero. It seems to be off right from the start though.

11-17-2004, 10:21 AM	#1
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,684	Speedo question/problem I have been driving my 70 4x4 this week. Been doing alot of work to her to get her ready for my wife to drive to work when the weather turns bad. I noticed that the spedo is off exactly 5mph compared to my GPS. Nothing surprising there. But I have noticed that every once in awhile, it will just drop about 5mph, then go back up. The needle doesn't really bounce, just out of the blue it will drop for 5 seconds to a minute, then pop back up. I am sure the 5mph off thing is in the calibration, but is the up and down thing a bad speedo? The odometer quit working years and years ago, so I wouldn't feel bad about throwing another one in there. Thanks for any suggestions. Also, anyone know the weight of a complete disc brake front crossmember? __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE

11-17-2004, 10:42 AM	#3
Project1970 14.1 @ 96MPH Join Date: Jul 2001 Location: Mesa, AZ Posts: 2,811	5mph off at ALL speeds? That's not a calibration error (or at least, not as far as speedo gears in the transmission are concerned). The gap should widen as speeds increase. __________________ Project1970 - LS1 Swap Complete!

11-17-2004, 10:47 AM	#4
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,684	Yeah, it is off by 5 at all speeds. If it says 25 the GPS says 30, if it says 55, the GPS says 60. The GPS is dead-nuts on compared to the speedo in my 03' Silverado, so I trust it. I have an extra speedo in the attic, I guess I'll put it in this weekend and see what happens. Thanks guys! __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE

11-17-2004, 12:02 PM	#5
68w/sbc406 Got Light Emitting Diode? Join Date: Apr 2004 Location: Newberg, OR Posts: 2,485	the speedo should be off by a % not a constant 5. as for the complete crossmember thing, they are heavy. it was all me and a friend could do to get it off of the ground to put it on jack stands __________________ 1968 1/2 ton 2wd lwb 6 lug disc and bags up front. Next c notch and rear bags '02 Chevy Silverado LT ext cab short bed 2WD 5/7 drop on 22's(the family car) 1993 Cherokee work ride/weekend wheeler

11-17-2004, 12:24 PM	#6
ale8oneboy Registered User Join Date: Jun 2003 Location: Pike County, KY Posts: 89	Would a different tire size affect this? __________________ MEMBER OF THE BUCKET SEAT CLUB (REAL BUCKETS) "Color Me Gone" - Two Lanes of Blacktop

11-17-2004, 10:32 AM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Sounds like the speedo is bad. I would try replacing it first. If it were a cable or gear problem the needle would bounce. Jim

11-17-2004, 12:27 PM	#7
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	It could be a zero error. The odometer issue is probably a plastic shaft inside the housing. I just had my speedo gone through at Bowtie Bits. Cleaned, calibrated, replaced the odometer shaft and painted the needle for $45. He has the work done in his shop. __________________ Fred There is no such thing as too much cam...just not enough engine.

11-17-2004, 12:48 PM	#9
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,684	The truck has stock heigth tires and original gears. I think I will replace it with another speedo I have and go from there. I am not too concerned about fixing this one since the odometer quite working about 40,000 miles ago Thanks all! __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE

11-17-2004, 01:23 PM	#10
Project1970 14.1 @ 96MPH Join Date: Jul 2001 Location: Mesa, AZ Posts: 2,811	So does it actually read zero when stopped? It sounds like it should read 5mph then. Yeah, the gauge itself is most likely broken. __________________ Project1970 - LS1 Swap Complete!

11-17-2004, 02:21 PM	#11
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,684	Yup, it reads zero. It seems to be off right from the start though. __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE

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