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5th gear lockout.
Posted: Sun May 29, 2022 8:38 pm
by gtrbg
Anyone run into a good way to do a reverse lockout on a roadster 5 speed. My Austin sprite 4 speed is easy with just a bar that I can fix in place so cannot go into reverse which is a dogleg off to the right with no 5th gear above. Other thing is the springs seem a bit weak on the 5 to 4 shift and I need to do very slow. I assume I need to tear the transmission apart to replace the spring.
Re: 5th gear lockout.
Posted: Mon May 30, 2022 2:36 pm
by jhayden
Disassembly is not required. The shifter springs can be removed easily from the bottom of the box after unscrewing the two hex bolts (a 15/16†six point socket works fine). Note that the two springs are different. Yes, the Car Parts Manual shows the same part nr., but the Rallye Parts Catalog (pp. 163-164) and The Roadster Store (now defunct) catalog (pp. 69-70) correctly show them as different, with the stronger spring for the 5-R plane.
Could your springs have been switched at some time? There really shouldn’t be a need to alter the FS5C71A (arguably the best box that ever found its way into a production car) to prevent missed shifts, as the springs cause the shift lever to default to the 3-4 shift plane. Try moving the shift lever to the left (1-2 plane) and then to the right (5-R plane). You should notice a stronger resistance to the right than the left.
If you do remove the springs, you can compare their lengths to those shown. These are used springs, but the box when removed showed no signs of spring fatigue.
Hope this helps. Please let us know what you find out.
Jon
Re: 5th gear lockout.
Posted: Mon May 30, 2022 5:29 pm
by GeoffM
jhayden wrote: ↑Mon May 30, 2022 2:36 pm
Disassembly is not required. The shifter springs can be removed easily from the bottom of the box after unscrewing the two hex bolts (a 15/16†six point socket works fine). Note that the two springs are different. Yes, the Car Parts Manual shows the same part nr., but the Rallye Parts Catalog (pp. 163-164) and The Roadster Store (now defunct) catalog (pp. 69-70) correctly show them as different, with the stronger spring for the 5-R plane.
Could your springs have been switched at some time? There really shouldn’t be a need to alter the FS5C71A (arguably the best box that ever found its way into a production car) to prevent missed shifts, as the springs cause the shift lever to default to the 3-4 shift plane. Try moving the shift lever to the left (1-2 plane) and then to the right (5-R plane). You should notice a stronger resistance to the right than the left.
If you do remove the springs, you can compare their lengths to those shown. These are used springs, but the box when removed showed no signs of spring fatigue.
Hope this helps. Please let us know what you find out.
Jon
Hey Jon, Does the 4-speed have the same spring arrangement?
Re: 5th gear lockout.
Posted: Mon May 30, 2022 6:40 pm
by Solex68
Great info Jon.
David Premo explained it to me on a drive at Solvang 2022 but I couldn't take notes at the time. You could also shim it if you needed a little adjustment.
Re: 5th gear lockout.
Posted: Tue May 31, 2022 4:26 pm
by jhayden
GeoffM wrote: ↑Mon May 30, 2022 5:29 pm
Hey Jon, Does the 4-speed have the same spring arrangement?
[/quote]
Geoff, regrettably (and to the disdain of the U.S. automotive press at the introduction of the 240Z) the spring-loaded 5 speed was only installed in the 2000 roadsters. When everything is working correctly, you get the feeling that you could shift almost as precisely and quickly whilst wearing a catcher's mitt or boxing gloves -- leave it to the springs to prevent missed shifts.
Solex68 wrote: ↑Mon May 30, 2022 6:40 pm
Great info Jon.
David Premo explained it to me on a drive at Solvang 2022 but I couldn't take notes at the time. You could also shim it if you needed a little adjustment.
Greg, thank you for posting and the adjusting suggestion, b/c last time I checked nos springs were nla. Who on this forum would not have watched and listened to a YouTube video of that drive with the two of you?
Re: 5th gear lockout.
Posted: Tue May 31, 2022 7:47 pm
by Solex68
Jon.
I too have tried to get the springs and I could not locate them in USA or Japan. Thank you for all the detailed information on how to test the trans springs and showing what the springs actually look like. I always thought they'd be bigger.
Re: 5th gear lockout.
Posted: Tue May 31, 2022 8:25 pm
by redroadster
I've found that s flat top shifter knob with thumb on top vs the ball knob helps in the 5th to 4th downshift .
Especially the pistol grip style some of the way back shifter arms are terrible about this 5 to 4 & R
If your down shifting to 4th likely your going 60+
Not a good time to slam the shifts anyway
Re: 5th gear lockout.
Posted: Wed Jun 01, 2022 12:32 pm
by mraitch
In a review of the roadster way back when, Stirling Moss himself commented about the roadster gearbox - "It''ll shift as fast as you can!"
Re: 5th gear lockout.
Posted: Wed Jun 01, 2022 3:59 pm
by iloveredmeat
Remember that time y'all said there are no stupid questions???
I'm going to hold you to that... sooo... What exactly is "5th gear lockout"?
Thank you,
Peter
Re: 5th gear lockout.
Posted: Wed Jun 01, 2022 5:21 pm
by rwmann
It’s not rocket science. Neither is the Fifth to Reverse likely. Especially with a shorter shifter and aluminum or Delrin bushings.
Re: 5th gear lockout.
Posted: Wed Jun 01, 2022 6:00 pm
by notoptoy
iloveredmeat wrote: ↑Wed Jun 01, 2022 3:59 pm
Remember that time y'all said there are no stupid questions???
I'm going to hold you to that... sooo... What exactly is "5th gear lockout"?
Thank you,
Peter
It's a mechanical or other method to prevent shifting from 5th to Reverse accidentally, particularly while moving forward at a high rate of speed.
Re: 5th gear lockout.
Posted: Wed Jun 01, 2022 8:32 pm
by unklpat
Jon, it's not the length, but the stiffness of the springs. I had a heated debate with a well known roadster transmission guy, and proved that the stiffer spring was in a certain place. 5th and reverse. right side, I think. If you want pictures, I can provide them. I don't have any info on replacements. Pat
Re: 5th gear lockout.
Posted: Thu Jun 02, 2022 8:13 am
by jhayden
That is correct: the photos show the stronger spring placed on the right side corresponding to the 5-R plane, and the explanation for that is to prevent accidental shifting to that plane. Greg is correct, though, that shorter spring length due to age may be compensated for with shims, since the oem springs are nla from Nissan.
Re: 5th gear lockout.
Posted: Thu Jun 02, 2022 9:54 am
by Mike Unger
I have one race prepared transmission that someone modified with a cable lockout for reverse. I never used it. It uses a hardened pin and a cable mount on the outside of case with a drilled hole and seal, The pin when engaged stopped movement of the shift rod into reverse unless you pulled the cable release with the other hand. If you're really interested in doing that much work I will try to dig it out and get you more info. I never liked the idea of having to use two hands to find reverse in case I "went agricultural" and needed to move quickly...I've also found that my downshifts were almost never 5th to 4th at the tracks I race, so I learned to ease the lever out of 5th to find center neutral and then up into 3rd. Let me know if you want more info.
Mike
Re: 5th gear lockout.
Posted: Thu Jun 02, 2022 1:22 pm
by iloveredmeat
notoptoy wrote: ↑Wed Jun 01, 2022 6:00 pm
iloveredmeat wrote: ↑Wed Jun 01, 2022 3:59 pm
Remember that time y'all said there are no stupid questions???
I'm going to hold you to that... sooo... What exactly is "5th gear lockout"?
Thank you,
Peter
It's a mechanical or other method to prevent shifting from 5th to Reverse accidentally, particularly while moving forward at a high rate of speed.
Thanks Tom... and I think we can all be happy that I won't ask why that might be a problem. I'm actually learning!
Thanks again, cool info.