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Datsun 5-speed transmission question (FS5W71B)


frankachino

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I'm not sure if this is normal, so I figured I'd see if anyone else has the same issue. I recently swapped the 4-speed out of my 240 for what I believe is a 5-speed out of a 1977-78 280. I noticed that 1st-4th all seem fine, but when shifting into 5th, the lever will spring back into the center (where 3rd would be). It seems to stay in 5th gear, but my worry is that when trying to shift out of 5th, if I do not manually push it back to the side where 5th is, it will mess something up. I had the transmission apart before I swapped it in to do some cleaning and general checks and didn't see anything "off". When looking at the striking rod itself, the grooves for the return plug would suggest this is normal.

Anyone have any experience with this?

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Yeah.. i think you need to replace those 3 bushings.. 2 on the side and one on the lower end.. you see it when you take it apart.. you cán get the 2 for on the sides in brass but the nylon ones will hold another 30 years.. so..

When the gearbox jumps out of gear (most times 5th) you have to take a look at the springs that are in the main plate in the middle of the gearbox, there are some ballbearings and springs under some big nuts.(on main plate.)

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3 hours ago, Mark Maras said:

 I'd look into the shifter bushing. Worn ones can create a lot of lateral movement.

I had also replaced those side bushings with the brass upgrades and a new bottom bushing as I thought those were the cause of the problem. It took all the slop out of the lever, but it still returns to center for the right most gears (5th and reverse). I have tried driving in 5th and it didn't pop out of gear (I haven't done much testing with that yet though). When I had it apart, I manually moved each fork and the detents were very firm. 

 

Excuse the crude drawing since I couldn't find any pictures online, but this is a cross section of my striking rod guide and what I saw. When it rotates into 1st or 2nd, the detent pin goes up that ridge and holds it there. But with 5th and R, it stays on that ledge and the force of the return spring and pin pushes it back to center. 

Striking Rod Guide.JPG

Striking Rod Guide.JPG

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Are you using the shifter stick from the F4W71B 240Z transmission or the one that came with the FS5W71B transmission?

There are different lengths between the horizontal achor pin (with the two plastic bushes) and the lower cup bush that fits jnto the striking rod. If that distance is too short it can slipe out of the striking rod in 5th and you will experirnce what you are describing.

If you look at the striking rod. The hole for the shifter is machined in a round striking rod. That means on the left and right side of the hole there will be a curved arch. This is where the cup can slipe out. I hope that makes sense.....

This could be your problem.

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28 minutes ago, EuroDat said:

Are you using the shifter stick from the F4W71B 240Z transmission or the one that came with the FS5W71B transmission?

There are different lengths between the horizontal achor pin (with the two plastic bushes) and the lower cup bush that fits jnto the striking rod. If that distance is too short it can slipe out of the striking rod in 5th and you will experirnce what you are describing.

If you look at the striking rod. The hole for the shifter is machined in a round striking rod. That means on the left and right side of the hole there will be a curved arch. This is where the cup can slipe out. I hope that makes sense.....

This could be your problem.

Howdy EruoDat, I'm using the stick that came with the FS5.

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15 hours ago, frankachino said:

when shifting into 5th, the lever will spring back into the center (where 3rd would be). It seems to stay in 5th gear,

Not clear how this could happen considering how the system works.  How does the end of the shift lever get past the 3rd gear rod fitting?  The 3rd/4th rod should be centered and therefore in the way.  I see roll pins.  Maybe something is loose.

image.png

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55 minutes ago, Zed Head said:

Not clear how this could happen considering how the system works.  How does the end of the shift lever get past the 3rd gear rod fitting?  The 3rd/4th rod should be centered and therefore in the way.  I see roll pins.  Maybe something is loose.

image.png

It confused me as well. It's impossible to see how it is moving while the tail housing is installed. I did notice the fork where the striking lever engages 5th/R is much larger than the 1st/2nd and 3rd/4th 

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51 minutes ago, Zed Head said:

Where did you get it?  What do you know about it?  Does it shows signs of being apart in the past?  

I got it from a previous project 280 I had about a year ago. The 280 had an L28et swap and it did look like the sealant on the midplate was not factory so I'm assuming when they swapped the motor, they took apart the transmission. I do know for sure its a wide ratio FS5W71B. The car that it was in had been sitting for quite a while outside in a field. It was attached to 

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