Speedometer problem

ox_ford_guy · #1 (**permalink**) 10-05-2006, 09:17 AM

Help...I was recently driving my cobra and the speedometer jumped wildly and then just quit. (It is a Autometer reverse reading unit) The trans is a Tremec T-5

I thought it might be the cable so I removed the old one and replaced it with a new assembly.
Although I am not totally sure how the speedo drive gear on the transmission end should look, I removed the clip and inspected the gear teeth and the square cable drive hole inside and it looked OK. I could see no evidence of damaged gear particles or anything else.

This speedo gear has the drive gear tooth configuation and a pointed round end shaft (on the far end away from the retaining clip) that is all part of the gear. The pointed end goes back into the trans first when reinstalling the cable assembly.

I re-installed the new cable with the original gear and clip as I had taken it out and the speedo still doesn't work.

If I undo the cable at the speedo end and turn the inside drive cable by hand it turns freely in the transmission with no notable resistance. (I would think it should be locked if engaged and working properly) It also does not turn on the speedometer end when driving.

Any ideas on where to look next or who can help would be greatly appreciated ...Thanks

undy · #2 (**permalink**) 10-05-2006, 09:41 AM

It sounds like a stripped drive/driven speedo gear in the tranny..

Still Looking · #3 (**permalink**) 10-05-2006, 10:40 AM

If I may jump in with a question about speedometers. Mine works, but it is never steady. Jumps up and down 10 mph constantly. Thoughts?

JBCOBRA · #4 (**permalink**) 10-05-2006, 11:18 AM

I have a speedometer issue as well. Mine seems to prefer being over 100! LOL
JB

ox_ford_guy · #5 (**permalink**) 10-05-2006, 11:30 AM

Undy..Thanks for the reply.....
Any thoughts on what might cause the drive/driven gear to strip? The trans is almost new, with only a few hundred miles on it

...Thanks

undy · #6 (**permalink**) 10-05-2006, 11:34 AM

Improper or unmatched gears, possibly a speedo cable that's intermittantly hanging up.

Ron61 · #7 (**permalink**) 10-05-2006, 11:38 AM

Still Looking,

If your speedometer jumps around it is normally a sign of two things. The cable has a bind in it somewhere or is about ready to break. It could be the speedometer itself but seldom is. That is easy to check. Just take the cable loose at the transmission and run it with an electric drill and see if it still jumps around. I have cured this in the past by pulling the cable from the sheath and lubercating it well.

Ron

xlr8or · #8 (**permalink**) 10-05-2006, 11:48 AM

You should not be able to turn the cable from the speedo end if the car is not moving. If the gear on the cable does not spin on the cable then it's going to need a new driven gear. If you have a reverser hooked up to your speedo you might want to check that and make sure is spins freely and add some grease.

pmfranke · #9 (**permalink**) 10-05-2006, 12:59 PM

what kind of grease?

RallySnake · #10 (**permalink**) 10-05-2006, 01:17 PM

Frankie,

The Slick 50 grease is great for all purpose use. I often use the black moly slip grease for this stuff, too. But, it's so hard to get off your hands and everything else.

Oxford,

Sounds like you have the wrong speedometer gear. You could do what I did. I went to Pick-a-Part and crawled under a bunch of Mustangs and collected drive gears of all colors. Now I'm ready for correcting the speedometer error. What color do you need? I might have the right one.

Paul

xlr8or · #11 (**permalink**) 10-05-2006, 01:55 PM

Quote:

Originally Posted by pmfranke

what kind of grease?

The same grease you would use for your wheel bearing would work just fine.

jarendall · #12 (**permalink**) 10-05-2006, 03:22 PM

go to www.johnsmustang.com look under late model mustangs and do a search on speedo gears, make sure you have the right gear for the T5

BlueRooster · #13 (**permalink**) 10-05-2006, 05:51 PM

For SPF call any dealership and order a new cable. Problem solved. The cable is the insert that goes inside the outer cable casing. It will take you 10 minutes to replace.

ox_ford_guy · #14 (**permalink**) 10-06-2006, 09:45 AM

Rallysnake/Jarendall/Xlr8or..Thanks for you replies.

I guess a wrong cable gear is possible as I did not install the trans. The previous owner did.

I went to johnsmustang web site and looked at the T-5 speedo gears and the one that is in the trans now is black and looks more like the ones pictured for automatic trans. (The non gear end looks longer than that on the T-5 gears)
I am going to contact Tremec to try to get info on the year of my trans core
so I can try a different speedo cable gear)

However, the configuration that is in there now did work for several hundred miles before something failed. Would this be possible if it is the improper cable gear match?

Also, if the problem is a stripped drive/driven gear in the tranny is it at all fixable without a total tranny removal...

Thanks again to all for the guidance as I am new to the Cobra world....ox_ford_guy

RallySnake · #15 (**permalink**) 10-06-2006, 10:55 AM

Oxford Guy,

The speedometer drive gear on the tailshaft of your transmission is made of very hard steel. The speedometer gear on the end of your cable is plastic. There is very little chance that anything is wrong inside your transmission, other than some broken plastic gear teeth floating around.

My guess would be that your plastic gear was a little too small in diameter and the tips wore off the teeth. There may have been too much drag somewhere in the cable (possibly due to too tight of a bend) that caused the problem. See if you can reinstall the cable with smooth larger radius curves. If not, you may need a longer cable. I actually linked two of them together to make a big loop in my engine compartment to avoid this problem.

I am leaving town for a few days, but I will look for a black gear for you when I return.

Paul

RallySnake · #16 (**permalink**) 10-06-2006, 11:08 AM

Oxford Guy,

If you're in a hurry, you can pick up one of these:

http://cgi.ebay.com/ebaymotors/2-For...spagenameZWDVW

http://cgi.ebay.com/ebaymotors/Ford-...spagenameZWDVW

http://cgi.ebay.com/ebaymotors/5-FOR...spagenameZWDVW

Paul

ox_ford_guy · #17 (**permalink**) 10-06-2006, 05:35 PM

Rallysnake...Thanks again for your advise.

I also was wondering why the internal trans gear would fail first. I was wondering if it was also plastic, but thought that would be a very poor design choice because of assessability and for a heavy duty/racing trans application. (after checking I.D. numbers with Rockland Standard Gear I found that my trans is a Tremec world class T-5)

I will pull the speedo cable again and check the number of teeth, for signs of wear and try to reroute the cable. However, there doesn't seem to be much extra to work with in the length. How did you junction the 2 cables together for the solution you mentioned?...Thanks....ox_ford_guy

ox_ford_guy · #18 (**permalink**) 10-06-2006, 06:11 PM

Rallysnake..I ordered 2 new black 20 tooth gears on E-Bayfor another try. Thanks for the lead...ox_ford_guy

pmfranke · #19 (**permalink**) 10-06-2006, 06:48 PM

thanks ,rally snake. solves another problem!

jarendall · #20 (**permalink**) 10-06-2006, 07:23 PM

the drive gear in my T5 is bronze, you should not have damaged it, go to the following web site to find out what tooth gear you will need for your setup: http://www.sccoa.com/faq/speedgr.html