NewZed Posted January 7, 2012 Share Posted January 7, 2012 I know that many people have done the Z/ZX transmission bell-housing swap on to the C type transmission to allow its use on the L6. How do they compare after a few miles of driving? Are the gear ratios better? It looks like the 1st to 2nd jump is pretty big, bigger than any of the other 5 speeds available. After you get to 2nd it looks about like a ZX 5 speed. How about shifting performance in general, with the dual cone 2nd gear synchro and newer gear box design in general. I have an extra bell-housing and a line on a 300Zx transmission, and the overall cost and effort looks less than a 5 speed rebuild. I'm on the fence but have time to think about it. Any driving impressions appreciated. Thanks. Quote Link to comment Share on other sites More sharing options...
pallnet Posted January 7, 2012 Share Posted January 7, 2012 I run this setup in my L28ET powered S13. It's a smooth shifting transmission if you get one that hasn't been abused by someone with ambitions of an amature race carear. You will need to shorten the driveshaft, relocate the shifter hole in most cases and mod the trans mount. I run the 240mm clutch in mine. Good luck pallnet Quote Link to comment Share on other sites More sharing options...
Nigel Posted January 7, 2012 Share Posted January 7, 2012 relocate the shifter hole in most cases pallnet Can you elaborate on this? Only very early Z's (< '71) may require relocating the shifter hole, and those aren't very common. I have an SX box in my '73, and I didn't have any issues. The shifter is centered in the console: And there's lots of room around the hole in the transmission tunnel... As for the OP's questions, I'm very happy with the SX box in my 240Z. I've no regrets about doing it, and I recommend it to anyone looking for a heavier duty transmission, assuming they get the version with extra wide gears and dual cone synchro on 2nd (not all the C boxes are the same). I wish 1st, 2nd and 5th were a little taller (3.7 rear end), but the shorter gearing is not something that's really obvious. I just have a cheap e-bay short shifter, and it's fantastic. The shifts are so short, but still light and positive. So much better than a ZX box. http://www.motortopi...sion-swap-14041 Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 7, 2012 Author Share Posted January 7, 2012 (edited) Thanks for the feedback! I've seen your comments on the atlanticz site pallnet (one of the first as far as I can tell), and been through your writeup many times Nigel. I almost have the procedure memorized. I went over to 240SXforums.com and downloaded some FSMs and they show the dual cone 2nd gear all the way back to 1989. The first dual cone appears to show up in 1988 in the 300ZX, which opens up the range for improved synchros. Haven't found any information on the wider gears yet. As for the shorter gears, the C transmssion has about the same first gear ratio as the early 77-79 boxes. So my 3.54 gears should work well, I would guess. I'v attached a little Excel plot I put together just to visualize the ratio differences. Still interested in comments or information, from anyone interested. Edited January 7, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 11, 2012 Author Share Posted January 11, 2012 For future reference if anyone comes across this thread - nylon zip ties work great for keeping the rear extension from popping off the adapter plate before the bellhousing, when trying to remove the housing for swapping or modifying. The bellhousing has two bearings holding it in place and the extension will break loose and try to fall off before the bellhousing. Once you get a small gap you can slip a zip tie or three threw some bolt holes and cinch the extension back tight to the adapter plate. I opened the extension/adapter plate gap back up afterward to clean up the sealing surface after I got the bellhousing off. I didn't see any need to pull the extension and wanted to avoid the usual problems that come up with the "while I'm at it" so just worked on the bellhousing. Also, take note that there is a snap ring on the outside of the main bearing and a circlip holding the inside. Only the snap ring needs to come off. If you remove only the circlip, the main bearing will come off the main shaft and stay in the bellhousing and the bellhousing will probably be more difficult to remove. Here's an interesting thread I found over on a Nissan diesel forum about the 71C transmission. Lots of good pictures and information - http://nissandiesel.dyndns.org/viewtopic.php?t=58 And here's another on the 71C swap in to a 240Z, very well written, comparable to Nigel's write-up - http://home.comcast.net/~zheimsothtn/transmission.htm Still interested in anyone's experience with the swap, for the record. Quote Link to comment Share on other sites More sharing options...
rejracer Posted January 15, 2012 Share Posted January 15, 2012 (edited) The first dual cone appears to show up in 1988 in the 300ZX, which opens up the range for improved synchros. Haven't found any information on the wider gears yet. Newzed, How did you find the which years had which synchro's? I have an 87 transmission, and would like to know if it has the double cone synchro. I've downloaded the 87 and 88 FSM's and in the 88 I seen referenced in the exploded view diagram "2nd inner baulk ring" and "2nd outer baulk ring" Is this what makes it a dual cone synchro box? Am I reading it correctly in that only 2nd gear has a double cone synchro on it? Also I've split the case on the 1987 and it had the wider 20mm gears vs the 17mm wide gears on a 280zx transmission. Thanks in advance for any insight. Edited January 15, 2012 by rejracer Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 24, 2012 Author Share Posted January 24, 2012 Newzed, How did you find the which years had which synchro's? I have an 87 transmission, and would like to know if it has the double cone synchro. I've downloaded the 87 and 88 FSM's and in the 88 I seen referenced in the exploded view diagram "2nd inner baulk ring" and "2nd outer baulk ring" Is this what makes it a dual cone synchro box? Am I reading it correctly in that only 2nd gear has a double cone synchro on it? Also I've split the case on the 1987 and it had the wider 20mm gears vs the 17mm wide gears on a 280zx transmission. Thanks in advance for any insight. Missed this post somehow. Yes, that is my take on the double-cone synchro. The synchronizer cone shown in between the rings in 1988 is the 2nd cone. The first cone is part of the gear itself. My 1985 71C also has the ~20 mm gears vs ~18 for the ZX. I'm not familiar with the S13/S14 world so can't speak to the comments on Nigel's motortopia web page about wider gears. He shows 20 mm as the wide gear. It looks like you get all of the major benefits from 88 on in the 300ZX. There were other modifications also, like a mainshaft brake, for synchro help I assume? (a weird little gizmo on the 3-4 shift rod, no explanation in the FSM), shown in the shifter diagram, introduced in 1987. So far, for the 300ZX 71 - wider gears from at least 1985 and on (probably 84 though), mainshaft brake 1987 and on, double cone synchro 1988 and on. And all 71Cs have the larger diameter CS bearing, I assume. Here is something interesting from zcarsource. The swapped 300ZX/71B bellhousing transmissions are available for sale, completed. Spendy. http://www.zcarsource.com/manual-5-speed-transmission-conversion-from-300zx-84-86-to-240z-260z-280z-rebuilt_8_52706_50262.html Quote Link to comment Share on other sites More sharing options...
Nigel Posted January 25, 2012 Share Posted January 25, 2012 Sorry for the confusion about the dual cone synchro on second. I'm not sure why I remember that as being unique to the later boxes. I tried to look at the actual microfische on carfische.com, but carfische doesn't seem to exist any more? Too bad if that's the case, because it was an amazing resource. Does the Z31 box have the synchro reverse? Nigel Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 25, 2012 Author Share Posted January 25, 2012 (edited) Just doing some homework and filling things in for the record, for the 300ZX 71C. You qualified your statements on Motortopia as for the 240SX box, so definitely not a problem. The early 300ZX 71Cs, 85 - 87, did not have the dual cone synchro so you were right. You showed a picture of an S13 box with narrow gears, but maybe that was a 71B box (as I said, I don't know the S13s). I think the question above is when the wider gears came about for the 300ZX, and it looks like the 300ZX has always had the wider gears (haven't verified 1984 though). It seems like the 1988 (edit- and 1989) 300ZX is the best 71C you can get from a 300ZX. The statement below is WRONG. 1989 had the 71C also. Looks like they stopped using it with the model change to Z32 in 1990. 1989 still had no reverse synchro. WRONG - Looks like they used the 71C last in 1988 - WRONG Reverse synchro would be nice, which would be an advantage of the 240SX box. I'd guess there's some other improvements also. Edited January 27, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 28, 2012 Author Share Posted January 28, 2012 (edited) Edit - My mistake, saved for future... Edited January 28, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
rejracer Posted January 30, 2012 Share Posted January 30, 2012 Just to confirm, they used the 71C in the 1989 300zx per the FSM. It also does not have the reverse synchro. I downloaded the 1995 240sx FSM from Nicoclub and found that the box has the double cone synchro on 2nd and a synchronized reverse. So it looks like the 240sx it the best box to use. I also found another thread that stated that the shifter location between the 240sx transmission and the RB20 transmission are in different location, with the 240sx being further back. It also stated the 240sx transmission is longer. What I've not found out is what type of internals are in a RB20DET 71C box. Any links appreciated Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 30, 2012 Author Share Posted January 30, 2012 (edited) I had also posted one more note on the 1989 300ZX 71C transmission, above, but deleted it. I was going to wait until I picked one up at the local Pick n' Pull on Saturday (20% off transmission week!), but the synchros were worn, and the main shaft scuffed up, and it was on its second life (prior wrecking yard marks) so I left it. One added benefit to the 1989 71C is that Nissan added a double cone synchro to 3rd gear too. So 89 appears to be the ultimate 300ZX 71C transmission, assuming, of course, that double cone synchros are actually a bonus. You can actually see the 3rd gear synchro setup through the filler hole, and tell the difference from the standard single cone, for anyone's future reference. I agree on the 240SX transmission, from my limited knowledge. It looks like they also went to sealed main bearings in the SX, I would guess as an improvement. No help from me on the RB transmission. Edit - Just looked at the 1995 240SX FSM and see that they don't use the double-cone 3rd gear. Maybe it was a modification that didn't stick? I've only experienced the 71B 5 speeds in use so don't know much. Edited January 30, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
rejracer Posted January 30, 2012 Share Posted January 30, 2012 Thanks for the info, I did not notice the 3rd gear synchro on the 1989 FSM when I opened it. I'm curious now if you can swap out the 3rd gear syncho or reverse synchro to have the best of both worlds. Bahh.. that breaks my custom parts rule, but still food for thought. Quote Link to comment Share on other sites More sharing options...
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