Tach Question? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

6T9GMC · 01-15-2004, 11:25 AM

I GOT THE TACH HOOKED UP ON MY TRUCK AND IT REALLY SUPRISED ME TO SEE HOW MANY RPM'S MY THESE TRUCKS TURN.
IT HAS A 307 ENG AND A THREE SPEED TRANNY, AND ON THE HIWAY IT WAS TURNING BETWEEN 3500-4000. DOES THIS SOUND RIGHT OR COULD THE TACHOMETER BE OFF?

THANKS

Dean · 01-15-2004, 11:33 AM

What rearend gears do you have?

SWEET7T · 01-15-2004, 12:06 PM

well for a comparison, I have 3.08's, and I turn 3000 running ~80mph

6T9GMC · 01-15-2004, 01:01 PM

I'M NOT SURE WHAT GEAR. IT IS A SHORT STEP SIDE PLANE JANE TRUCK
WITH NO A/C OR ANYTHING. WE PUT POWER STEERING ON IT.

JimKshortstep4x4 · 01-15-2004, 01:09 PM

The truck probably has a 3:73 in it, but depending on the speed the tach could be off. The tachs are adjustable and with a reference tach, it is pretty easy to do.

Jim

6T9GMC · 01-15-2004, 01:55 PM

HOW DO YOU ADJUST IT? I'M GONNA PUT A TIMING LIGHT ON IT AND SEE IF IT IS OFF, BUT IF IT IS HOW DO YOU ADJUST IT?

THANKS

Perchjerker · 01-15-2004, 02:01 PM

That sounds right to me. I have the same set up in my all original truck and it screams at 70.

JimKshortstep4x4 · 01-15-2004, 03:06 PM

If you look on the back of the tach there is a small piece of tape covering the adjustment screw. Just hook up a second tach, (known to be accurate and adjust your tach to match).

Jim

6T9GMC · 01-15-2004, 03:15 PM

I didn't know that. That is pretty cool. Thank you for the help!

01-15-2004, 11:25 AM	#1
6T9GMC Registered User Join Date: May 2003 Location: MOORE, OK Posts: 146	Tach Question? I GOT THE TACH HOOKED UP ON MY TRUCK AND IT REALLY SUPRISED ME TO SEE HOW MANY RPM'S MY THESE TRUCKS TURN. IT HAS A 307 ENG AND A THREE SPEED TRANNY, AND ON THE HIWAY IT WAS TURNING BETWEEN 3500-4000. DOES THIS SOUND RIGHT OR COULD THE TACHOMETER BE OFF? THANKS

01-15-2004, 12:06 PM	#3
SWEET7T Try spinnin 4 rear tars Join Date: Sep 2003 Location: Salt Lake City, Utah Posts: 757	well for a comparison, I have 3.08's, and I turn 3000 running ~80mph __________________ SWEET7T 1970 C10, 2wd, LB, 307/TH350/3.08. PS, PB

01-15-2004, 01:01 PM	#4
6T9GMC Registered User Join Date: May 2003 Location: MOORE, OK Posts: 146	GEAR I'M NOT SURE WHAT GEAR. IT IS A SHORT STEP SIDE PLANE JANE TRUCK WITH NO A/C OR ANYTHING. WE PUT POWER STEERING ON IT.

01-15-2004, 01:55 PM	#6
6T9GMC Registered User Join Date: May 2003 Location: MOORE, OK Posts: 146	TACH IS ADJUSTABLE? HOW DO YOU ADJUST IT? I'M GONNA PUT A TIMING LIGHT ON IT AND SEE IF IT IS OFF, BUT IF IT IS HOW DO YOU ADJUST IT? THANKS

01-15-2004, 02:01 PM	#7
Perchjerker Beer Power!!!!!!!!!! Join Date: Nov 2003 Location: Nacogdoches, TX Posts: 280	That sounds right to me. I have the same set up in my all original truck and it screams at 70. __________________ Rather be fishin'

01-15-2004, 11:33 AM	#2
Dean Senior Member Join Date: Jan 2000 Location: Cincinnati, Ohio Posts: 1,492	What rearend gears do you have?

01-15-2004, 01:09 PM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	The truck probably has a 3:73 in it, but depending on the speed the tach could be off. The tachs are adjustable and with a reference tach, it is pretty easy to do. Jim

01-15-2004, 03:06 PM	#8
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	If you look on the back of the tach there is a small piece of tape covering the adjustment screw. Just hook up a second tach, (known to be accurate and adjust your tach to match). Jim

01-15-2004, 03:15 PM	#9
6T9GMC Registered User Join Date: May 2003 Location: MOORE, OK Posts: 146	THANKS! I didn't know that. That is pretty cool. Thank you for the help!



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