ARE THERE ANY TECHS HERE???
Thread Starter
Instructor
Joined: Oct 2002
Posts: 123
Likes: 0
From: So CA
ARE THERE ANY TECHS HERE???
car is 89 6-speed,
speedo sometime does not work or jumps up and down, mostly at slower speeds and more often in cooler weather,
is this the sending unit in the trans?
any ways to test?
thanks!
bill
email replies are ok too: billwineberg
speedo sometime does not work or jumps up and down, mostly at slower speeds and more often in cooler weather,
is this the sending unit in the trans?
any ways to test?
thanks!
bill
email replies are ok too: billwineberg
Burning Brakes
Joined: Dec 2003
Posts: 770
Likes: 0
From: Madison Mississippi
Re: ARE THERE ANY TECHS HERE??? (billwineberg)
Bill, I am not a tech but, I have seen this problem before. My problem was identical to yours. It was my speedo cable....I believe yours is lacking lubricant and if you take it out, you need to change it. I recall it was under twenty dollars and not too terribly difficult. It would be a good time to purchase the Service manual to remove and re-install without damaging anything. good luck, I hope I get a second on this diagnosis
Mike :auto:
Mike :auto:
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Re: ARE THERE ANY TECHS HERE??? (RUBYREDVETTECARD)
Uh... cable??? Doubt it, check the connector at the sending unit at the tail shaft of the trans. No cable on my '90, only wires to send the signal.
Thought I saw a post a week or so ago about someone having the plastic gears in the sending unit get stripped?
Thought I saw a post a week or so ago about someone having the plastic gears in the sending unit get stripped?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: ARE THERE ANY TECHS HERE??? (Trog)
Uh... cable??? Doubt it... No cable on my '90, only wires to send the signal.
RACE ON!!!
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
Re: ARE THERE ANY TECHS HERE??? (CFI-EFI)
*lol* okay... somehow I expected the earlier version w/ digital dash etc. all had sending units like mine.
assumption = butt-u-mption
(doah - darn swear editor.)
[Modified by Trog, 4:03 PM 3/2/2004]
assumption = butt-u-mption
(doah - darn swear editor.)
[Modified by Trog, 4:03 PM 3/2/2004]
Thread Starter
Instructor
Joined: Oct 2002
Posts: 123
Likes: 0
From: So CA
Re: ARE THERE ANY TECHS HERE??? (CFI-EFI)
fairly positive it has NO cable, I was under there in the summer changing the u-joints and I'm a maintenace freak and changed the gear oil too, so I would have lubed a speedo cable if it had one, while at it i even smoothed and polished the driveshaft!
and I know my '88 GTA Trans-Am L98 5.7 TPI, 700R4 trans had an electrical sender where the old speedo cable would go... pretty sure the '89 C4 is the same setup...
thanks guys!
hopefully someone will be able to help me diagnose this problem.
Burning Brakes
Joined: Dec 2003
Posts: 770
Likes: 0
From: Madison Mississippi
Re: ARE THERE ANY TECHS HERE??? (billwineberg)
Not trying to beat a dead horse here....the reason I suggested cable is, the problem you are describing acts mechanical not electrical. Your symptoms would be consistant at all times if it were electrical; not effected by speed or temperature. My 2 cents :)
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Thread Starter
Instructor
Joined: Oct 2002
Posts: 123
Likes: 0
From: So CA
Re: ARE THERE ANY TECHS HERE??? (RUBYREDVETTECARD)
just looked definitely it IS electrical!
the VSS (vehicle speed sensor) has spinning magnets or something inside to send a signal to the VSSB (vehicle speed sensor buffer) so i can see it being effected by speed and temp, the VSSB I doubt would be erratic.
I was hoping there was someone here with info on how to diagnose the speedo system and test the VSS.
or someone who had a similar problem on a C4 and would report what worked for them.
Drifting
Joined: Oct 1999
Posts: 1,722
Likes: 0
From: Gloucester Va
Re: ARE THERE ANY TECHS HERE??? (billwineberg)
WOW a cable???? LOL
it is a VSS. It beats at 4000 pulses per mile at 60 MPH. This signal is sent to the dash where it is halfed into 2000 pulses per min at 60 MPH. ON an auto car it is normally sent to the ECM so it knows when to lock the converter up. However you don't have a auto, but it is still sent to the ECM.
It is indeed magnets that spin inside the speed sensor. If you have jumping chances are the signal is being lost then brought back really quick, the gears as mentioned are messed up in the tranny causing it to slip maybe and then catch making your speed jump.
Check you wires first make sure non are bad, then replace the speed sensor.
it is a VSS. It beats at 4000 pulses per mile at 60 MPH. This signal is sent to the dash where it is halfed into 2000 pulses per min at 60 MPH. ON an auto car it is normally sent to the ECM so it knows when to lock the converter up. However you don't have a auto, but it is still sent to the ECM.
It is indeed magnets that spin inside the speed sensor. If you have jumping chances are the signal is being lost then brought back really quick, the gears as mentioned are messed up in the tranny causing it to slip maybe and then catch making your speed jump.
Check you wires first make sure non are bad, then replace the speed sensor.
