4 Speed Bell Housing swap to 5 Speed Case : FS5W71B : Reverse Switch Modification

[zKars]

Today's little task is to choose a 5 speed to add to my latest 510 project.

Decided on one that is a bit of an un-known. It "looks" like the 82-83 ZX close ratio trans case, long ears, one exhaust hanger, reverse lock out blah blah blah EXCEPT it has a front case that has the rotated clocking for an L motor that would be mounted vertically rather than at our 12 degrees CW slant. Big deal, I've been hoarding 4 speed bell housings for various swaps, so I'll just go get one of those.

Quickly it reminded me that while it bolts right on, the 4 speed housing reverse switch is in different spot than on the 5 speed housing. Well the only difference is that it is pretty much 7/8" farther to the rear.  What to do. There are only these options:

1. Do without reverse lights.  

2. Drill a new hole in the 4 speed case 7/8" further forward, plug the old hole.

3. Modify the shift rod to move the indent where it needs to be to activate the reverse switch in it's current location.

4. Go choose a 5 speed with the right bell housing to begin with, dipstick....

Enny meany miney moh...

 

 

[zKars]

Let's review pro's and con's:

1. Do without reverse lights. 

• Well if you left the switch in and hooked up you'd have reverse lights all the time. No.

2. Drill a new hole in the 4 speed case 7/8" further forward, plug the old hole.

• Sounds simple enough, you have to have the right size tap and drill bit, and if you look closely, that dang thing is not 90deg to the case, it's kinda angled. The nose of the switch has to be in the JUST the right spot. And you'd have to experiment with spacers since there is no raised area on the case like the stock one, and it might leak, and .....  No.

3. Modify the shift rod to move the indent where it needs to be to activate the reverse switch in it's current 4 speed location.

• This is my choice. The rest of the thread is about how to do this easily. 

4. Go choose a 5 speed with the right bell housing to begin with, dipstick....

• No fun just doing the simple thing is there?

 

[zKars]

Here is the visual on the switch locations

Four Speed, 

 

Five Speed, further forward.  7/8 further forward.

 

 

Inside, here is the 4 speed reverse shift rod with it's indent

 

and here is the 5 speed reverse shift rod with it's indent.

Switch tip sits where the blue line is in neutral, then as the fork is pushed forward as you go into reverse, the switch plunger tip climbs that ramp and depresses the switch turning on the reverse lights. 

Note the longer flat part to the right of the tip. This allows the reverse switch to remain OFF when the trans in 5th as the rod is pulled back. Handy. 

Edited July 21, 2022 by zKars

[zKars]

So what do we have to do to modify the shift rod?

Simple. Here I have sharpied-in the location of the depressed/ramp area on the 4 speed shift rod, onto the 5 speed shift rod. And cleverly spliced and sized a little picture of the 4 speed slot so can visualize how it has to look.

If you just duplicated the 4 speed slot you'd leave an untouch area between the two where the rev lights would be turned on for a second as you shifted into 5th. Would give following drivers pause no doubt "did he just shift into reverse for a second there!?!?!?!" so

So what you need to do, is recreate the "ramp" end where shown, and grind the rest of the meat to the right of that, to be just flat to meet the existing flat area. To say another, just keep grinding the existing ramp away until you have moved it to the left to the left most sharpie line, ie where it is on the 4 speed.

Get your dremel, or your angle grinder, or your carbide tipped grinding burr, and get removing material. I'd start by cutting down at the far left edge of where my new extended flat is going to be (right most sharpy line) and then remove material to the right to create the new extended flat area. Then cut my new ramp.

Clearly you will want to thoroughly wrap the entire guts of the transmission with something like saran wrap or palette wrap or tons of shop towels so that nothing but that short area of the rod is exposed. Chips in here would spell disaster.

You can take the rod out of the transmission of course and remove all that "shavings everywhere" risk, but it means removing the 1-2 and 3-4 rods first, seven little balls and three springs to loose, three cotter pins to punch out and put back, so do what you're comfortable with. 

I'm going to go do this work and report back with a picture of the finished modified shift rod.

Precision is not important. The flat part does not have to really flat, the ramp can be smooth or lumpy, it just has to END (get back to un-reduced OD) 2-15/16 ( 2.9375) 74.5mm in front of the center plate with the transmission in neutral. And the flat has to start at 3-3/16" from the center plate so the switch is fully extended (off) when the trans is neutral.

How do you know you are neutral?

All three shift fork channels are lined up with each other perfectly.

Edited July 21, 2022 by zKars

[zKars]

And for you wussies that are afraid of weakening that rod by grinding it down, just stop those slam shifts while into 5th and reverse. 

The shift fork for 5-R is in behind the center plate, and all the rod in front does is support it straight in the front housing.  I'd be shocked if you could break it. All the fierce shifting in the world won't bend that rod.

[Zed Head]

2 hours ago, zKars said:

EXCEPT it has a front case that has the rotated clocking for an L motor that would be mounted vertically rather than at our 12 degrees CW slant.

Maybe it's from one of the 4 cylinder NAP?  ZAP? ... NAPS-Z twin plug engines.  Apparently they were vertical.  Did you measure the length?  That's another possible difference.  Gear ratios might be interesting also.

From the cloud.  I don't know much, just remember them from the wrecking yard in the small trucks. - 

https://en.wikipedia.org/wiki/Nissan_NAPS

https://en.wikipedia.org/wiki/Nissan_A_engine

 

Edited July 21, 2022 by Zed Head

[zKars]

Regular length, I did count teeth and computed ratio’s, will post. Doesn’t match exactly any of the ZX usual 3 suspects.

[zKars]

 

First column is this trans, next 3 are 81-83 close,  80-81 then 77-79

3.321		3.062	3.062	3.321
1.902		1.858	1.858	2.077
1.308		1.308	1.308	1.308
1.000		1.000	1.000	1.000
0.833		0.745	0.773	0.864

[zKars]

Had a chance to take that shift rod out and make the changes to it.

Cheated a bit and used a mill to extend the flat area, then used a flap wheel on my angle grinder to create the ramp at the end. 

[zKars]

Then when cleaning the rear housing, I discovered the end isn’t exactly round anymore. 

Used a bolt and nut and some force spreading rings and got it better. Bit afraid to push to hard and crack the aluminum casting.  Mind you it dented pretty easily without cracking. Might have to warm it “slightly” to increase ductility.

Nice that the opening is just a hair under 2.00 inches (1.97), I have some 2” pipe I use as backups and support.

 

Edited July 22, 2022 by zKars

[zKars]

There seems to be no end of lessons to be learned around here.

Seems it is in fact NOT a good idea to heat up the end of the extension housing to soften it to help straighten out that ding. It was not the aluminum case that suffered, it was the bronze or whatever it is bushing inside that literally melted. I found a puddle of what I would swear was solder on the bench where it had landed. 

And the no one on earth seems to have any NIS-62 bushings available. Out of Stock is the key word of the day.

And full circle, I am now onto option 4 as above, go get a real 5 speed with the right bell housing and just put it in.  Humph.

[heyitsrama]

https://www.allstategear.com/FS5W71-Extension-Housing-Bushing-p/nis-62.htm

 

https://sales.omegamachine.com/Nissan_FS5W71C_Extension_Housing_Bushing_p/71411.htm I had to order one for my gearbox rebuild, the shipping is $25 bucks so get that wallet out.