700R4 Speedometer drive gear - The 1947 - Present Chevrolet & GMC Truck Message Board Network

blackBAMAsilverado · 10-16-2013, 03:09 PM

Fluid is leaking where the speedometer cable is connected to the transmission. It's a 1983 C10 with 305 V8 and 700R4 transmission. Mechanic said he thinks the drive gear has a worn spot since a new seal didn't help. Does anyone know what number of teeth, or what color this gear would be? Also where can I order one?

Keith Seymore · 10-16-2013, 03:45 PM

I don't know offhand, but if it is a non-electronic trans it doesn't seem like it would take much to pop it out of there and take a look...

K

kalbert · 10-16-2013, 09:58 PM

Quote:

Originally Posted by Keith Seymore

I don't know offhand, but if it is a non-electronic trans it doesn't seem like it would take much to pop it out of there and take a look...

K

+1 Just take it off and count the teeth.

bnoon · 10-16-2013, 04:29 PM

Wondering how either the drive or driven gear would cause a leak... If the outer O-ring seal didn't fix the leak, perhaps the adapter housing itself is leaking. The gear just slips onto the inside part and doesn't stick out through the housing.

EDIT: I guess it kinda comes close to the inner edge of the housing and would seal on the shaft part of the driven gear... that might cause a leak. It is one bolt to pull it out and take a look though, after you unscrew the cable. At worst you have a few drips of fluid, but just point the truck nose first down hill and you should be good.

gchemist · 10-16-2013, 05:03 PM

What is your rearend gear ratio? Go here to find the part number: http://www.73-87.com/7387garage/drivetrain/speedo.htm

To know for sure, you have to pull out the driven tooth housing and check.

geezer#99 · 10-16-2013, 10:55 PM

Not sure if it applies to a 700 but if you put in a new speedo housing, the inner oring that seals the drive gear isn't pushed down inside the housing and it will leak. My t350 was like that. The maker of the housing expects the mechanic to know that and seat it correctly. Mine hadn't been done by the po and it had a groove in the gear by the incorrectly seated oring and we had to replace the gear and housing.
Your mechanic nailed the cause of the leak.

Rascal_one2001 · 10-17-2013, 09:56 PM

The easiest fix is spend the $120 and get the brand new speedo gear set and housing there is a guy my shop deals with on eBay he will need to know your tire diameter and rear end gear ratio and sends the correct tooth count for your speedo to be accurate

10-16-2013, 03:09 PM	#1
blackBAMAsilverado Registered User Join Date: Aug 2013 Location: Albertville, AL Posts: 4	700R4 Speedometer drive gear Fluid is leaking where the speedometer cable is connected to the transmission. It's a 1983 C10 with 305 V8 and 700R4 transmission. Mechanic said he thinks the drive gear has a worn spot since a new seal didn't help. Does anyone know what number of teeth, or what color this gear would be? Also where can I order one?

10-16-2013, 03:45 PM	#2
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,226	Re: 700R4 Speedometer drive gear I don't know offhand, but if it is a non-electronic trans it doesn't seem like it would take much to pop it out of there and take a look... K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/

10-16-2013, 04:29 PM	#4
bnoon Registered User Join Date: Jul 2012 Location: Des Moines IA Posts: 1,250	Re: 700R4 Speedometer drive gear Wondering how either the drive or driven gear would cause a leak... If the outer O-ring seal didn't fix the leak, perhaps the adapter housing itself is leaking. The gear just slips onto the inside part and doesn't stick out through the housing. EDIT: I guess it kinda comes close to the inner edge of the housing and would seal on the shaft part of the driven gear... that might cause a leak. It is one bolt to pull it out and take a look though, after you unscrew the cable. At worst you have a few drips of fluid, but just point the truck nose first down hill and you should be good. __________________ - 1981 Sierra 454, NV4500 swap - 2006 Z06, 25k miles - 1973 Nova - Project CarNova Virus on Youtube Last edited by bnoon; 10-16-2013 at 04:40 PM.

10-16-2013, 05:03 PM	#5
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: 700R4 Speedometer drive gear What is your rearend gear ratio? Go here to find the part number: http://www.73-87.com/7387garage/drivetrain/speedo.htm To know for sure, you have to pull out the driven tooth housing and check. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

10-16-2013, 10:55 PM	#6
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,731	Re: 700R4 Speedometer drive gear Not sure if it applies to a 700 but if you put in a new speedo housing, the inner oring that seals the drive gear isn't pushed down inside the housing and it will leak. My t350 was like that. The maker of the housing expects the mechanic to know that and seat it correctly. Mine hadn't been done by the po and it had a groove in the gear by the incorrectly seated oring and we had to replace the gear and housing. Your mechanic nailed the cause of the leak.

10-17-2013, 09:56 PM	#7
Rascal_one2001 Registered User Join Date: Dec 2006 Location: North Carolina Posts: 308	Re: 700R4 Speedometer drive gear The easiest fix is spend the $120 and get the brand new speedo gear set and housing there is a guy my shop deals with on eBay he will need to know your tire diameter and rear end gear ratio and sends the correct tooth count for your speedo to be accurate __________________ 1985 1500 454, 4l80e, 12 bolt, 5/6 drop, 20s



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