Swapped Rears.....speedo Way Off...help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

nejeff · 07-05-2003, 01:49 PM

Just completed swapping rears from a 72 Custom 10 (307, 3 speed) into my 72 Super Cheyenne(350, auto) and the speedo is now running fast, unsure yet of how much but looks like about 10 mph at least.

Also I seemed to have bumped things up enough that the center support bearing thing( unsure what you call it) is whining real bad. Took a look and can move it all around with my hands easy. What is the name of the piece so I can call Oreilly's

Thanks guys for your help

flyinbass · 07-06-2003, 05:28 AM

nejeff,
I have a 1970 Longhorn fleetside with a 350/350 and a 1-ton rearend. I replaced the third member (was a limited-slip) for a possi-track rearend. The engine ran fast, the transmission shifted quickly and I was going about 25 mph. The speedometer read about 75mph. The third-member was from a truck with a manual transmission and is geared lower than one out of an automatic (in my case anyway). I think the "center support bearing thing" you refer to is the 'Carrier' bearing for the two piece driveshaft in longbed trucks.

Regards,
Gary R70

nejeff · 07-06-2003, 05:29 PM

Thanks alot Fly! Found the carrier bearing at Oreilly's.

rodnok1 · 07-07-2003, 01:25 PM

the easiest fix is to take your truck out on the expressway and go mile marker to mile marker and check your speedo read out. i.e. actual mileage 1 mile, speedo reads 1 mile 3 tenths. Take this info and your old gears and holder(as it may change) to a good trans or speedo shop. They should be able to give you correct gears based of your info. Good luck

**COBALT** · 07-08-2003, 04:41 PM

Yeah, you need a different speedo gear in your transmission. if you unscrew the cable you'll see that the plate should come off and allow you to turn the speedometer gear out of the transmission. Its driven by a worm gear off of the output shaft. Knowing what to replace it with may take some doing...

07-05-2003, 01:49 PM	#1
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	Swapped Rears.....speedo Way Off...help Just completed swapping rears from a 72 Custom 10 (307, 3 speed) into my 72 Super Cheyenne(350, auto) and the speedo is now running fast, unsure yet of how much but looks like about 10 mph at least. Also I seemed to have bumped things up enough that the center support bearing thing( unsure what you call it) is whining real bad. Took a look and can move it all around with my hands easy. What is the name of the piece so I can call Oreilly's Thanks guys for your help __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

07-06-2003, 05:28 AM	#2
flyinbass Registered User Join Date: May 2003 Location: Vail, Arizona Posts: 3	nejeff, I have a 1970 Longhorn fleetside with a 350/350 and a 1-ton rearend. I replaced the third member (was a limited-slip) for a possi-track rearend. The engine ran fast, the transmission shifted quickly and I was going about 25 mph. The speedometer read about 75mph. The third-member was from a truck with a manual transmission and is geared lower than one out of an automatic (in my case anyway). I think the "center support bearing thing" you refer to is the 'Carrier' bearing for the two piece driveshaft in longbed trucks. Regards, Gary R70 __________________ Gary R70

07-06-2003, 05:29 PM	#3
nejeff Registered User Join Date: Jun 2003 Location: Nebraska Posts: 63	Thanks Thanks alot Fly! Found the carrier bearing at Oreilly's. __________________ 72' Chevy Super Cheyenne LWB 72' Chevy C-10 (307 Parts Truck)

07-07-2003, 01:25 PM	#4
rodnok1 Registered User Join Date: Jun 2003 Location: Linden, North Carolina Posts: 617	speedo fix the easiest fix is to take your truck out on the expressway and go mile marker to mile marker and check your speedo read out. i.e. actual mileage 1 mile, speedo reads 1 mile 3 tenths. Take this info and your old gears and holder(as it may change) to a good trans or speedo shop. They should be able to give you correct gears based of your info. Good luck

07-08-2003, 04:41 PM	#5
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Yeah, you need a different speedo gear in your transmission. if you unscrew the cable you'll see that the plate should come off and allow you to turn the speedometer gear out of the transmission. Its driven by a worm gear off of the output shaft. Knowing what to replace it with may take some doing... __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.



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