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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 84chevysilverado on February 19, 2009, 07:04:16 pm

Title: changing speedo o ring
Post by: 84chevysilverado on February 19, 2009, 07:04:16 pm

so my 700r4  is leaking around where the speedo shaft goes into transmision. I took the speedo cable off and took off the bolt that holds on the little cover covering the speedo gears. but i cant take off the cover, how big is this cover and where does it meet the tranny so i can pry it off? 

Title: Re: changing speedo o ring
Post by: HAULIN IT on February 19, 2009, 08:53:22 pm

It's not really a cover like you may be thinking. It is more of a round slug with a groove around it for an O-ring IN a bore, so from the outside there isn't anything to "pry it off"... it's a "slide it out" deal. Maybe try squirting around it with penetrating fluid & scraping the edge of the bore a bit. Good Luck, Lorne

Title: Re: changing speedo o ring
Post by: Russ130 on February 19, 2009, 11:27:53 pm

Yes be careful with it. That holds the driven gear in mesh with the drive gear for the speedo. I usually try and spin it a bit first then I rock it a little as I'm pulling it out. I never use pliers or anything other than my hands to remove it.

Title: Re: changing speedo o ring
Post by: 69byrd on February 20, 2009, 07:32:32 am

I replaced mine and I rocked it alittle as I pulled and it came out.

Title: Re: changing speedo o ring
Post by: 78 Chevyrado on February 20, 2009, 10:53:36 am

if I remember right, here's how it all goes together:
(http://www.transmissionsone.com/64_38cutawayspeedogear.jpg)

and here's what the part you take out looks like, the threaded part is where the speedo cable goes:
(http://www.transmissionsone.com/700Gear3.jpg)

Title: Re: changing speedo o ring
Post by: HAULIN IT on February 20, 2009, 03:44:01 pm

Nice pic's Kenny!

Title: Re: changing speedo o ring
Post by: VileZambonie on February 20, 2009, 04:10:21 pm

There's a bulletin on the 700R4 for leaks at the speedo. I'll post it here in a sec.

Title: Re: changing speedo o ring
Post by: VileZambonie on February 20, 2009, 04:16:19 pm

Number: 87-138
 
Section: 7A
Date: May, 1987
Subject: FLUID LEAKS FROM THE PLASTIC SPEEDOMETER DRIVEN GEAR/ADAPTOR AREA
 
 ALL LIGHT DUTY TRUCKS WITH MANUAL OR AUTOMATIC TRANSMISSIONS

(http://i6.photobucket.com/albums/y228/Sabaka454/speedo.gif)

Figure No. 1EXTENSION AND ASSOCIATED PARTS
 

BULLETIN COVERS:

Transmission fluid leak at the plastic speedometer driven gear (44, Figure No. 1) can be caused by a hole in the driven gear shaft. In some cases, this condition could be misdiagnosed as a speedo driven gear fitting leak (43, Figure No. 1).

(http://i6.photobucket.com/albums/y228/Sabaka454/speedo1.gif)

Figure No. 2
 
 SERVICE ACTION:

When servicing a vehicle for a fluid leak around the speedometer driven gear fitting or cable, check the speedometer driven gear shaft for a hole through the center of the shaft as follows: (Figure No. 2)

1. Install a hand vacuum pump over the end of the gear (opposite gear teeth).
2. Pump up 10 in.-hg. of vacuum.
3. The gage should stay at 10 in.-hg for at least 30 seconds. -If the gear holds vacuum, inspect the seals in the adaptor. -If the gear does not hold vacuum, replace the gear.*

*Note: Check the new gear from parts stock as outlined before installing in transmission.
SERVICE PARTS:

Refer to the GM Service Parts Operations (GMSPO) Catalog for the current speedometer gear based on transmission model and year.
 
 

Title: Re: changing speedo o ring
Post by: 84chevysilverado on February 20, 2009, 08:00:01 pm

thanks guys ya really helped me out
thanks marc :D