Speedo/Transmission
Thread Starter
Intermediate
Joined: Jun 2005
Posts: 48
Likes: 0
From: Queen Creek AZ
Speedo/Transmission
Hey Guys and Gals
I am sure this has been asked before but here we go again.
I am working a a 1978 C3 with Automatic Transmission with criuse control and the speedo is not working.
I replaced the lower cable which was burnt but still no luck.
This caused me to investigate further the cable from the crusie control box to the speedo is fine and when i spin it the needle on the speedo moves, the cruise control box turns when i spin either cable and the 'external' drive piece on the transmission works too.
From what i can tell and see there is an 'Orange' drive piece in the transmission that may be broken (its hard to see), the question is/are......
Is it possible to remove this piece without removing the transmission and if so how ?
Plus any other suggestions would be gratefully recieved.
Gary
I am sure this has been asked before but here we go again.
I am working a a 1978 C3 with Automatic Transmission with criuse control and the speedo is not working.
I replaced the lower cable which was burnt but still no luck.
This caused me to investigate further the cable from the crusie control box to the speedo is fine and when i spin it the needle on the speedo moves, the cruise control box turns when i spin either cable and the 'external' drive piece on the transmission works too.
From what i can tell and see there is an 'Orange' drive piece in the transmission that may be broken (its hard to see), the question is/are......
Is it possible to remove this piece without removing the transmission and if so how ?
Plus any other suggestions would be gratefully recieved.
Gary
Last edited by jagvette; Jan 12, 2013 at 07:14 PM.
Melting Slicks
Joined: Aug 2012
Posts: 2,548
Likes: 379
From: Woodinville WA
You didn't mention which automatic transmission.... but at least there's only two choices of housings:
this (turbo 400)
and this (turbo 350)
both come apart the same way -
Unscrew the cable housing from the transmission (channel locks work good for this)
there's a 3/8 headed bolt with a clip attached to the transmission
take that bolt out
put the clip off to the side (preferably in a place you will find it later)
put a small drip pan on the ground under the housing
GENTLY, using channel locks or similar, work the speedometer gear housing out of the transmission case (it's held in the case with pressure and a rubber o-ring).
once removed, some fluid will leak out (aren't you glad you put something to catch it?)
most of the gears fail where the cable goes into the plastic gear housing (relatively easy to tell, the hole is now round instead of square like the cable)
now, should you have it apart and nothing looks wrong - it's possible that you simply didn't get the cable into the plastic gear when you reassembled - it's possible to put it together where the cable is actually riding against the plastic gear.... don't ask me how I know this as the words I'd use would injure a sailor's ears.
do post pictures
this (turbo 400)
and this (turbo 350)
both come apart the same way -
Unscrew the cable housing from the transmission (channel locks work good for this)
there's a 3/8 headed bolt with a clip attached to the transmission
take that bolt out
put the clip off to the side (preferably in a place you will find it later)
put a small drip pan on the ground under the housing
GENTLY, using channel locks or similar, work the speedometer gear housing out of the transmission case (it's held in the case with pressure and a rubber o-ring).
once removed, some fluid will leak out (aren't you glad you put something to catch it?)
most of the gears fail where the cable goes into the plastic gear housing (relatively easy to tell, the hole is now round instead of square like the cable)
now, should you have it apart and nothing looks wrong - it's possible that you simply didn't get the cable into the plastic gear when you reassembled - it's possible to put it together where the cable is actually riding against the plastic gear.... don't ask me how I know this as the words I'd use would injure a sailor's ears.
do post pictures
Burning Brakes
Joined: Oct 2010
Posts: 1,192
Likes: 7
From: Wentzville MO
I am in the process of removing my factory cruise but when my speedo didn't work it was 2 things. 1 the speedo itself and 2nd the Transducer 
.
I tested the transducer using my cordless drill and slowly turning the cable that connects to the trans. With the cable removed from the back of the speedo it should turn. Make a tap flag so you can see the cable turning.
.I tested the transducer using my cordless drill and slowly turning the cable that connects to the trans. With the cable removed from the back of the speedo it should turn. Make a tap flag so you can see the cable turning.
