If you're anything like me then you are always looking for high value upgrades for a low cost. That was my mindset as I was looking for a new transmission for my Z31. After the NA2T swap, my Z was pushing more HP then the stock 71c was prepared for, having already lived a somewhat hard life before I got it, and had started making some pretty terrible sounds akin to marbles in a blender when I would accelerate.
I knew there was really only 1 transmission that I would want to put in the Z and that is the FS5R30a that came in the 87-89 Turbo Z31, all Z32's, and a variation of it in the Pathfinder, Xtera, and Hardbody/Pickup. After many failed attempts to procure a Z31 specific transmission and even its Z32 counterpart, I decided to check in my local You Pull It for one of the variations of the 30a.
A quick note about the differences between the transmissions:
Z31 30a: Will bolt right up with all existing hardware
Z32 30a: Will bolt right up, but requires the use of the Z32 starter and Maxima flywheel (cannot use 8 bolt Z32 flywheel on the 6 bolt Z31 Crankshaft). Requires cutting of the shifter hole or shortened shifter bracket like this one offered from Xcessive Manufacturing. You will also have to "clearance" your transmission tunnel just a tiny bit for the reverse mounted starter to clear, usually achieved with a sledge hammer.
Pathy/Xtera/Hardbody 30a: Will bolt right up with the same hardware, but has a different shifter than both Z31 and Z32, and has shorter gear ratios as they are designed to be truck transmissions.
Note that you can pretty much mix and match most of these transmission parts for the correct specs. For example: a Z32 Transmission with a Pathfinder/Z31 Bellhousing will allow you to retain the stock flywheel and starter.
Years for the 30a Variation transmission:
Pathfinder/Hardbody: 1987-2000
Xterra/Frontier: 2000-2004
I knew there was really only 1 transmission that I would want to put in the Z and that is the FS5R30a that came in the 87-89 Turbo Z31, all Z32's, and a variation of it in the Pathfinder, Xtera, and Hardbody/Pickup. After many failed attempts to procure a Z31 specific transmission and even its Z32 counterpart, I decided to check in my local You Pull It for one of the variations of the 30a.
A quick note about the differences between the transmissions:
Z31 30a: Will bolt right up with all existing hardware
Z32 30a: Will bolt right up, but requires the use of the Z32 starter and Maxima flywheel (cannot use 8 bolt Z32 flywheel on the 6 bolt Z31 Crankshaft). Requires cutting of the shifter hole or shortened shifter bracket like this one offered from Xcessive Manufacturing. You will also have to "clearance" your transmission tunnel just a tiny bit for the reverse mounted starter to clear, usually achieved with a sledge hammer.
Pathy/Xtera/Hardbody 30a: Will bolt right up with the same hardware, but has a different shifter than both Z31 and Z32, and has shorter gear ratios as they are designed to be truck transmissions.
Note that you can pretty much mix and match most of these transmission parts for the correct specs. For example: a Z32 Transmission with a Pathfinder/Z31 Bellhousing will allow you to retain the stock flywheel and starter.
Years for the 30a Variation transmission:
Pathfinder/Hardbody: 1987-2000
Xterra/Frontier: 2000-2004
30a (left) and 71c (right) compared to each other. Although the 30a is shorter, it is significantly heavier than the 71c and substantially larger in diameter which was extremely visible once it was installed in the transmission tunnel.
The Pathfinder Swap
I lucked out at my You Pull It and found a 30a in a '92 Pathfinder (note the transmission must be from a 2wd V6 model, not the 4wd), and after spending a few hours in the dirt pulling it from the car I was able to get it back home. At first glance I thought it was just a regular Z32 casing with different gears inside but I quickly noticed the shifter and rear case housing were quite different meaning I could not use the Z32 shifter bracket and would have to make a custom solution.
The Pathfinder shifter housing with a single shift rod that connects to a 71c style shifter.
|
The Z32 shifter which uses a dual shift rod setup where one rod extends out the rear of the casing, offset from the center of the transmission.
|
A Custom Shifter
Using my 71c as a template, I measured the length from the top front of the bellhousing to the location of the shifter pivot position, and found the shifter from the Pathfinder and to be extended by 4-5 inches to get it close to the stock Z31 position. This would require the actual shift rod itself to be extended past the rear of the transmission case. Fortunately for us, there is a freeze plug located right in the correct spot for the shifter linkage to be extended through.
Here was my plan for how to extend the shifter correctly:
Salvage the shift rod from my 71c and weld it to the existing parts to retain the neutral/reverse lockout functionality of the pathfinder shifter. Then pass the rod through a bearing located where the freeze plug used to be to allow for support during shifts, while being able to slide and spin freely. This was then welded to a U-joint I found on Amazon meant for a steering shaft, and then a bracket was built to connect it to the Z32 short throw I also purchased on Amazon.
Here was my plan for how to extend the shifter correctly:
Salvage the shift rod from my 71c and weld it to the existing parts to retain the neutral/reverse lockout functionality of the pathfinder shifter. Then pass the rod through a bearing located where the freeze plug used to be to allow for support during shifts, while being able to slide and spin freely. This was then welded to a U-joint I found on Amazon meant for a steering shaft, and then a bracket was built to connect it to the Z32 short throw I also purchased on Amazon.
The bearing which adapts the 30mm freeze plug to an 18mm shaft, and then an 18 to 16mm sleeve to adapt to the 16mm shift rod from the 71c. I used high temp silicone to seal the bearing just as a precaution incase it wanted to leak at all.
After I had finished installing the bearing, I was slightly concerned about it being pushed in or out during use, although the silicone was doing a good job of keeping it in place. I decided on creating some small brackets to make sure it would not be able to slide out using some 1/8th aluminum I had laying around from when I created my custom front splitter. The brackets surrounded the bearing but not the shaft allowing for the bearing to be held in place securely without restricting any motion.
The aluminum bracket inside the transmission to ensure the bearing would not slip inwards
|
The aluminum bracket outside the transmission to ensure the bearing would not slip outwards
|
Inside the transmission I had a new piece fabricated from part of the 71c shifter linkage and the pathfinder shifter linkage to create a piece that adapts from the 18mm Pathy rod to the 16mm 71c rod while retaining the shifters neutral and reverse lock out functions, and also using the stock wrist pins to connect everything allowing for everything to be easily taken apart.
The shift rod is a combination of the 16mm shifter rod from the 71c and a universal joint I found on Amazon. I had to heavily modify this joint to make it work the way I wanted it to by cutting the weldable end off of one side to make it as short as possible, and the other side was cut down and a hole cut through it for the bracket that attaches it to the shifter itself.
The bracket that connects the shift rod to the new Z32 short shifter is very important and actually went through a lot of modification before it came out just the way it needed. This bracket is extremely important because it transmits the side to side motion of the shifter into rotational motion of the shift fork. It is extremely important that the bracket is very stiff and doesn't flex at all because any flex in the bracket is lost rotation from the swing of the shifter. In order to fix this bracket as tight as possible I ran a 3rd rod through it with nuts acting as a spacer so the bracket has 3 points of contact to minimize flex, and is not forced to be super tight on the other 2 pivot points adding friction to the mechanism.
The bracket also cannot be 100% fixed to either the shift rod or the shifter itself as it has the important job of pivoting on both the shift rod and the shifter as the shifter is moved front to back. The ball end of the shifter moves in an arc motion meaning the bracket must be able to move up and down to accommodate for this.
The bracket also cannot be 100% fixed to either the shift rod or the shifter itself as it has the important job of pivoting on both the shift rod and the shifter as the shifter is moved front to back. The ball end of the shifter moves in an arc motion meaning the bracket must be able to move up and down to accommodate for this.
Please note that I hate this bracket
It is ugly, complicated, and probably won't last very long despite being held together with lots of high strength Loctite.
Moving the shifter back would give more space between the U-joint and the shifter which would have allowed for a better bracket to be made similar to this one offered by Loj Conversions which is billet and has no opportunity to flex at all due to the way it is constructed.
It is ugly, complicated, and probably won't last very long despite being held together with lots of high strength Loctite.
Moving the shifter back would give more space between the U-joint and the shifter which would have allowed for a better bracket to be made similar to this one offered by Loj Conversions which is billet and has no opportunity to flex at all due to the way it is constructed.
The Shifter Bracket
Now that I had all the internals figured out, it was time to design a custom shifter bracket which would seal the hole in the top of the transmission left by the no longer usable, and about 1ft long pathfinder shifter, and also stretching backwards to hold the new Z32 short throw shifter.
I used some 1/4 Inch aluminum I had laying around and it was a great fit. It was strong, light, and easily machinable to get it to the dimensions I needed. I drew up the shifter in CAD and 3d printed a template for my shifter so I knew everything was exactly in the place it should be.
NOTE: the shifter hole was pushed back by about another half an inch or so in the final product compared to what is in the below sketch and really could have been pushed back further to create a better shifter feel.
I used some 1/4 Inch aluminum I had laying around and it was a great fit. It was strong, light, and easily machinable to get it to the dimensions I needed. I drew up the shifter in CAD and 3d printed a template for my shifter so I knew everything was exactly in the place it should be.
NOTE: the shifter hole was pushed back by about another half an inch or so in the final product compared to what is in the below sketch and really could have been pushed back further to create a better shifter feel.
The dimensions of the bolt holes on a pathfinder transmission. All measurements in mm.
The final version with the shifter installed.
How the shifter lined up in the car. It could have been pushed back another inch or so to increase the ergonomics of the shifts.
Mounting the 30a in the Car
Finally it was time to put everything together and install it in the Z. Because the 30a is significantly heavier, I had a fun time trying to wrangle the thing onto my transmission jack, but once it was lifted up it actually installed quite easily. Because I was using a pathfinder bell housing, the starter and flywheel bolted right up.
There is only 1 part you need to modify, and this is only if your Z is a 1984-86. Because the "Zenki" generation of Z31 never came with a 30a the transmission mount bolt holes do not line up. However I found there was a very easy fix for this. Some people drill new holes (although it is pretty close to some other bolt holes so I would worry about tear out) and some people bend the bracket to make it line up with the factory holes. I found an even easier way and that was to simply slot one hole. Where the transmission mount bushing connects to the transmission mount itself, it is just a single bolt holding it together. This was easily slotted and allowed for the mount to be pushed backwards about 3/4 of an inch to reach the near bolt holes. This is an easy, simple solution that should not have any negative side effects as the transmission should not move forwards and backwards along the slot, and the engine mounts are fairly stiff (especially if you have a solid mount like me).
There is only 1 part you need to modify, and this is only if your Z is a 1984-86. Because the "Zenki" generation of Z31 never came with a 30a the transmission mount bolt holes do not line up. However I found there was a very easy fix for this. Some people drill new holes (although it is pretty close to some other bolt holes so I would worry about tear out) and some people bend the bracket to make it line up with the factory holes. I found an even easier way and that was to simply slot one hole. Where the transmission mount bushing connects to the transmission mount itself, it is just a single bolt holding it together. This was easily slotted and allowed for the mount to be pushed backwards about 3/4 of an inch to reach the near bolt holes. This is an easy, simple solution that should not have any negative side effects as the transmission should not move forwards and backwards along the slot, and the engine mounts are fairly stiff (especially if you have a solid mount like me).
The stock mount is very close to a set of bolt holes, but needs to be moved just a bit to work well.
|
This is part of the transmission mount where the bushing attacked to the mount.
|
Here is the hole after being slotted. It's not the prettiest but it doesn't need to be.
Final Impressions: Would I recommend the Pathfinder swap?
Honestly it's hard to say I wouldn't. I think for the price point ($200 for the transmission, and maybe another $100-$150 in various parts and pieces) its certainly a viable option as long as you have the tools and knowledge to fabricate your own shifter. I have only driven the car with the new transmission for about 10 minutes so far as it turns out the junkyard transmission I got was pretty worn and also sounds like marbles in a blender, but the gear ratios in the "truck 30a" isn't bad in my opinion. If you know my channel then you also know I have a Miata and if you know anything about Miatas, they have incredibly short gearing, cruising at about 4k RPMS around 75 mph vs the 71c at about 3k rpms. I wasn't able to get any rpm vs speed readings for the Pathfinder yet, but when I do I will add them here.
Here is the gearing ratios between the Z32 30a and the Pathfinder 30a:
........ Z32 Pathfinder
1st 3.21 3.58
2nd 1.93 2.077
3rd 1.30 1.36
4th 1.00 1.00
5th 0.75 0.811
As you can see the gearing isn't actually too much different. It is shorter but pretty much 2nd to 4th are pretty much the exact same and even 5th is pretty close. Overall I wouldn't call the gearing that much shorter, and it definitely didn't feel that short when driving it.
The one part I wasn't satisfied with was the throw of the shifter itself, but not from 1st to 2nd or 3rd to 4th. Im talking about the side to side going from neutral to first, and first to reverse for example. It takes up pretty much the entire throw that the shifter has which is probably around 6-7 inches from side to side. I don't know if you could slam shift between 2nd and 3rd because of the distance it has to travel. But for a cruising, big power maker it isn't the end of the world.
I will try to drive with the Pathfinder transmission more in the coming weeks as it works fine when not thrashing it, and I will be testing some upcoming products for the Z in it and will need it to drive, but as for now I am on the hunt for another good working transmission. What kind of 30a is still to be seen, it really just depends on what's available around me at a good price point. If that happens to be another Pathfinder transmission, I wouldn't even bat an eye as it would give me a good opportunity to fix the few things I wasn't satisfied with and I pretty much have the entire setup ready to go.
Here is the gearing ratios between the Z32 30a and the Pathfinder 30a:
........ Z32 Pathfinder
1st 3.21 3.58
2nd 1.93 2.077
3rd 1.30 1.36
4th 1.00 1.00
5th 0.75 0.811
As you can see the gearing isn't actually too much different. It is shorter but pretty much 2nd to 4th are pretty much the exact same and even 5th is pretty close. Overall I wouldn't call the gearing that much shorter, and it definitely didn't feel that short when driving it.
The one part I wasn't satisfied with was the throw of the shifter itself, but not from 1st to 2nd or 3rd to 4th. Im talking about the side to side going from neutral to first, and first to reverse for example. It takes up pretty much the entire throw that the shifter has which is probably around 6-7 inches from side to side. I don't know if you could slam shift between 2nd and 3rd because of the distance it has to travel. But for a cruising, big power maker it isn't the end of the world.
I will try to drive with the Pathfinder transmission more in the coming weeks as it works fine when not thrashing it, and I will be testing some upcoming products for the Z in it and will need it to drive, but as for now I am on the hunt for another good working transmission. What kind of 30a is still to be seen, it really just depends on what's available around me at a good price point. If that happens to be another Pathfinder transmission, I wouldn't even bat an eye as it would give me a good opportunity to fix the few things I wasn't satisfied with and I pretty much have the entire setup ready to go.