Weak return to center spring

[Jarvo2]

I had the complete opposite issue...I wasn't able to move the shifter to the right (4spd into reverse) without totally using two hands to muscle it over. I removed the two springs, cleaned them up and reinserted and now I've got 'normal' spring return to center....not great, but normal for the vintage of the transmission. I found it easiest to remove the shifter boots from the top & access the bolt from there rather than snaking up around the exhaust from below.

[Mikes Z car]

To add info I ordered the return to center spring and the plunger it pushes on for a 5 spd using the part numbers in the dealer fiche, they are both still available (where does Nissan keep this material?). Per the fiche the spring comes in a package of 10 and the plunger in a package of 5 if that is the case I will give away the spare ones for shipping though the price they quoted was so cheap, something like $1.99 for the spring and the plunger is something like $11 that if you want the spring it might actually be cheaper to order it from the dealer!

Return spring P/N 32852-24901

Plunger the spring pushes on P/N 32851-N9000

Edited June 11, 2013 by Mikes Z car

[Captain Obvious]

Mike, If you do in fact end up with baggies of both parts instead of singles, I'd gladly take one of each off your hands and split your cost 50/50. Keep us posted!!

[Mikes Z car]

Captain Obvious,

That is a good idea on splitting the shipment 50/50 if I get baggies of parts. I will post here what I receive, the gentleman at the parts counter said the order will take 4 days to get here. I think I remember their parts counter is open until noon on Saturday. That fiche I got from the store on classiczcars.com helped with this. Sorta makes we wish I could see on Nissan's parts storage shelves to see what Datsun parts are laying around. I'll take one of those, two of those... Maybe an entire Z could be built from them?

Mike

[Mikes Z car]

To update I was told that the spring and plunger have been backordered from Japan and the parts should be here by the end of June. I was told that usually if the part is no longer available it gets canceled immediately.

[Mikes Z car]

Replacing the spring and plunger didn't make any real difference on the weak return to center which might not be surprising I imagine given that the measurements of the old and new springs and plungers are very similar.

Measurements (note length of old spring fully compressed):

Closeup of both old and new springs and plungers:

Plunger view from spring:

Old spring being measured just to validate my caliper reading (38.84MM):

There seems to be a "detent bias" on my car so that the return to center force is much greater pulling out of the 5th/reverse slot and letting go of the shifter as opposed to pulling out of the 1st/2nd slot and letting go. My 5 SPD DD doesn't have that bias, both return to center forces are the same. I don't know if the bias on my Z is indicative of wear on the shift rod. That doesn't seem likely to me, maybe the transmission return to center was like this from the factory due to the shift rod detent being ground differently on one side of center compared to the other?

Captain Obvious does your car have that same return to center bias?

It might be possible to cut the spring in half and then to place a metal cylinder or cut off bolt where the missing half of the spring was to increase the spring rate and thereby the force the spring is putting on the shift rod detent if the length of the cylinder is selected properly. Cutting the spring in half would still allow putting the spring/plunger back in with the fingers as long as the cylinder isn't too long. The stock spring is already fairly compressed so care would be needed to make sure the spring didn't get completely squished so it would run out of "compression travel". Minimum compression travel would be the thickness of the "ridge" on the plunger that contacts the shift rod. Maybe an even stouter spring is needed. Anyone have insights on this?

I only got 1 spring and 1 plunger as opposed to the fiche showing QTY of 10 and 5 respectively though looking at the baggies they came in the plunger baggy was originally marked for a QTY of 5 which someone marked out and replaced with a "1". The white sticker in the plunger baggy picture was on top of the more yellow colored sticker. The spring baggy looks like it is 30 years old but shows a QTY of 1.

Plunger baggy, white sticker was on top of yellow sticker as I received it:

Spring and Plunger baggies:

Plunger baggy large white sticker with QTY 5 marked out with marks a lot:

(Picture taken by backlighting with the sun)

Edited July 6, 2013 by Mikes Z car

[EuroDat]

Good to hear you got it working better Mike.

The reason it returns from 5th/reverse is stronger is because the way the groove in the selector shaft (pos 18 in my post#5 and your post #14) is made.

The groove has a shape angle on one side and the other side is half that. That gives you the strong push out on the 5Th/reverse line.

There is another thread on this: http://www.classiczcars.com/forums/engine-drivetrain-s30/48693-shifter-return-spring.html If you look in post#11 you will see the groove Im talking about and the two differant shoulders which produce the strong or weaker return.

Its doing what it should be doing. 1st/2nd is always softer. To make the detent stronger you could try to shorten the spring and compensate length with washers. There is room in the plunger and nut so you could experiment with the old spring. This will make the 5th/reverse also a lot harder.

Chas

Edited July 6, 2013 by EuroDat

[Mikes Z car]

EuroDat,

Thank you for the information and the thread link. Now that I know the return to center is supposed to be stronger pulling out of 5th I can make the spring stronger.

5th/reverse doesn't have much return to center force now so making it stronger shouldn't hurt anything theoretically.

Mike

[Captain Obvious]

Mike, I've got the bias you described. On my 5 speed, the return force away from 5/R is greater than the return force away from 1/2.

It's not enough to prevent me from clipping reverse, but I do have that bias.