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L16 automatic transmission to l20b need help!


scumie510

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Hi I noticed when trying to bolt the l16 auto trans to my l20b that the flex plates are different. L16 was a 5 bolt and the l20b was a 6 bolt. So my question is what flex plate do I need to make this work? Do I need a certain one? Or can I just pick one up at o'reillys for a 280z automatic? I was told to get one from a 280z from a few people so I assume that's right. Well hoping! Thank you

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For a '69 510 that might be a problem as they are not Nissan (JATCO) made, but Borg Warner units. The April '71 and on 510 use the JATCO 3N71B. Later 6 bolt crank L20Bs used them also and possibly an L20B flex plate could be used.

 

The earliest 240z used a 3N71A and 3N71B automatic

 

The chances of a 6 bolt mount L20B auto flex plate fitting a BorgWarner torque converter is.... (unlikely) You could try it though. You may need to drill four new holes for the torque converter.

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It is also possible that you may need to do some other things to the transmission.  Automatic transmissions get info on shift points, how hard to shift, etcetera, from the vacuum modulator.   The L-20-B puts out more torque than a L-16.   The L-20-B may also operating at a higher vacuum than the L-16 would, to supply the same power.

So the transmission would actually be applying less clamping pressure to the clutch plates, while the L-20-B is making more torque.

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The Z flex-plate will bolt up....but the spacing of the torque converter is critical.

 

And the holes will likely be off as stated for the torque converter.

 

I had a little experience trying to find a replacement flexplate for the Auto in my other wagon.(L16)

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Thank you all! It's actually for my 70 4dr. I just had the trans all rebuilt and and rebuilt the l20b. We want to keep it automatic so I will give the other plates a shot and see what happens. I'm hoping it works. We wanted to get it ready for Manteca meet and then drive it to nc from Cali.

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Be aware!  The early 510s used the British Borg Warner BW-M35 automatic transmission not the later Muncie Indiana BW-T35 automatic transmission!  The British unit uses a mechanical downshift cable tied in to the Hitachi SU carb throttle shift mechanism.  The American Muncie unit uses a vacuum modulator!  They are not bolt on compatible and never will be!  Built in incompatibility.  You cannot "Vaccum shift" a mechanically rigged transmission, nor can you "mechanically" shift a vaccum shift equipped automatic transmission!

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Isn't there a steel ring that slips on the back of the crankshaft that acts as a spacer or locator for the flex plate? It has been so long since I pulled my auto out I can't quite remember. I don't know if the one from an L16 crank will fit on an L20 crank. I suspect it is something that needs to be there.

 

Len

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Might be a good idea to post a picture of the transmission. With 510s being so old, a lot of stuff gets swapped and (with luck) you may have a 3N71B in it which might be easier getting a later 3N71B L20B flex plate to fit.

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The part number for the L16 crankshaft plate (fits on crank ahead of the flex plate) is the same for all L16s with BW and 3N71B automatics.

 

The flex plate is the same for all 510 BW automatics, but different for the later 3N71B JATCO

 

The pilot converter plate that bolts on the rear of the flexplate, sandwiching it to the crank and aligning the torque converter, is unique to the BW and does not match the later 3N71B auto converter.

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"I don't know if the one from an L16 crank will fit on an L20 crank."

L-16, five holes for flywheel or flexplate bolts

L-20-B, six holes for flywheel or flexplate bolts.

I  meant would the spacer/ring around the back of the crank interchange? I suppose when they added the 6thl bolt to the L20 crank the diameter of the rear of the crank was enlarged and the rings don't interchange. I need to head for my parts pile with a calipers just to satisfy my curiosity about the rear crank diameters.

 

Len

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Yeah...... doomed.

 

I would find an L20B auto flex plate... it will fit the L20B crank but you will need the L20B converter pilot and crank spacers that match it.

 

Top and bottom right...

transautodriveplatespacerLarge.jpg

 

The top one is the converter pilot and this aligns the torque converter to the crank center line, then the 4 mounting bolts on the converter are tightened. Just hope the BW converter fits the L20B converter pilot and that the flex plate fits in front of the converter. You can use washers between the converter and the flex plate if needed.

 

 

Sorry the converter pilot fits over the crank, then the flex plate then the spacer. The torque converter nose fits through them all and into the converter pilot at the front.

datsun521019.jpg

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Don't know if I have any to spare, like to keep them with the transmission.

 

Surely there are lots that are closer to you.

The pilot for the converter for the L20B is #12330-E3000 and is common to all L powered Z cars  810 and Maxima gas engines ( L24(E), L26, L28) all L20Bs, Z20, Z22, Z24s that had an automatic.

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