Bouncing MPH?

[Pomorza]

Hello all

Ok so this past weekend I took my Z out for a nice ride. As I live in Tucson and only really drive to school and back on week days I rarely ever really get it going over 35. Well yesterday I had it going a "bit" faster. While cruising back home I noticed that my speedometer bounces at 45mph. Most of my drive was on some nice long and twisty mountain roads so I wasn't really pay attention to the speedometer as much as the road and thus I didn't notice if was occurring at higher speed.

Has anyone had this problem? I run REDLINE MT-90 in the transmission and RL 75w90 in the rear.

Any help would be great

Jan

[Inf]

I would probably oil your speedometer cable. You can search for it, and there are threads about how to do it

[Pop's Z]

What he said. I had the dreaded speedo bounce and solved it by buying a graphite tube at NAPA. I emptied the whole thing into the cable at the speedo end. Accessing that particular part is not fun. I had my dash off at the time so it was easy. Once done, the speedo is steady at all speeds. Good luck getting your hands back there. Do yourself a favor and take off the steering wheel and take the seat out. More room for under-dash contortions. Wear eye protection, too. You will get some on your face.

Cheers, Mike

[Z train]

In Tucson,you really need to step up to the 75/140 weight oil.As for the speedo.Take the cable out and douche out the cable housing with brake cleaner then let it dry.Merles sells a speedo cable lubricant.

[Pomorza]

I couldn't find the post you guys are talking about. Could someone give me a link. Secondly, why would I use such heavy oil? 140 is a bit up there is it not? Is it just because of the heat or is there other reasons?

Jan

[Inf]

http://www.classiczcars.com/forums/showthread.php?t=7941&highlight=bouncing+speedo

I searched for "bouncing speedo" and there you have it...

The search button is in the blue bar at the top, 3rd link from the right. I don't know how you can even navigate the site in a practical way without it

Edited November 9, 2009 by Inf

[moritz55]

In one of my earlier 73 240z's , the nylon speedo gear in the pinion had several teeth missing or chewed up. It must have been removed and replaced incorrectly at some point causing the gear to wear. While you have your Speedo cable out - remove the speedo pinion and check the teeth on the nylon gear. Nissan can order them they just need to know the # of teeth and gear color.

Here is the link .. look at post #3. It has the Nissan PN's for the various speedo gears in the pinion - you can match your's up with. Looks like Courtesy Nissan also sells the pinion gears.

http://www.classiczcars.com/forums/showthread.php?t=6997&highlight=speedometer+pinion

One additonal point - I use 75W90 Valvoline in my tranny & rear end. When you change or drain your transmission oil, try to save it and measure how much you removed. Your oil may be low and thus the Speedo gear may not be getting lubricated properly, especially it's chewed up or damaged. I recented changed my tranny oil and it was actually overfilled by 12oz by the prior owner which caused it to leak out the rear at the shift selector, so make sure your car is level when refilling the tranny oil up to the fill hole.

Good luck and keep us posted ...

Edited November 9, 2009 by moritz55

[jalexquijano]

I recently installed a Brand new speedometer cable to my 1972 240z with a 280z 5 speed transmission and it is bouncing between o to 40 mph. I dont think a Brand new cable needs any kind of oil? Could i be missing some part at either of the ends of the cable? Or is this an issue because of the 5 speed tranny?

[S30Driver]

Was it doing it prior to the new speedo cable?

 

If so, its probably the 43 year old  speedo head itself that needs an overhaul, or replacement.

[Zed Head]

Could be that one of the ends is not seated correctly, probably the transmission end.  I've found that there's enough play in the sheath to get the fitting partially tightened and have that happen.  Take the transmission fitting off, pull the cable out partway, and insert it into the transmission.  Then slowly tighten the fitting while rotating the propeller shaft.  That way you'll know the trans. end is in, and the odds are good that the speedo end will slip in like it should.

[jalexquijano]

Could be that one of the ends is not seated correctly, probably the transmission end.  I've found that there's enough play in the sheath to get the fitting partially tightened and have that happen.  Take the transmission fitting off, pull the cable out partway, and insert it into the transmission.  Then slowly tighten the fitting while rotating the propeller shaft.  That way you'll know the trans. end is in, and the odds are good that the speedo end will slip in like it should.

Before replacing the cable it bounced when it reached 60 mph. Now it is the other way around it bounces from 0 to 40 mph. My mechanic is asking me for the relation of the differential/ Final Drive Ratio? Its a 1972 240z with a 280z transmission with center forcé clutch. Anyone???

[grannyknot]

1972 rear end should be 3.34:1 I think.