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Step by Step how-to: Auto to manual conversion


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#1 Zeddophile

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Posted 24 January 2008 - 05:54 PM

Dragged out of hiding, I wrote this a couple of years ago after converting my auto 260 to manual using a 280zx gearbox, and since then keep being unable to find it when someone asks how to do it and whats required.  This list should have every part required for the conversion, and the steps should hold true for most conversions, although keep in mind my car was a late 260, there may be some differences to a 240.

Thanks to StevoGJ for the photos supplied, and confirmation of details with the late 260 conversion.  Anyone who would like to contribute experience from an earlier car would be most welcome.
Thanks also to Lurch for the comprehensive list of donor gearboxes in the thread linked to shortly below.

PARTS:
- You'll need a gearbox.  See this thread for possibilities and discussion thereof: what gearboxes fit?
- Remember to get the gearlever with it, or one to suit.  The levers may differ between the possible donor gearboxes.
- Manual brake pedal and and clutch pedal (also one of the bolts at the top which retain the pedal, along with the plastic bushes and return spring (See second photo, Step 5, items B and C), you will remove another bolt and spring from your auto brake pedal). 280zx pedals are NOT suitable, 240 and 260 may interchange (unconfirmed)
- Flywheel (bolts to the crankshaft)
- Clutch friction and pressure plates + thrust bearing (usually all in one kit when bought new, I wouldn't bother getting secondhand personally, bolts to the flywheel),
- Spigot bush for the rear of the crankshaft, should be available from the same place as your clutch kit (Brake shops, Repco etc)
- Clutch fork and pivot (if not already in the bellhousing of gearbox)
- clutch master cylinder and the little pin (See second photo, Step 5, item C) that attaches the pushrod to the clutch pedal (NOTE: 280zx master cylinders have the bolt holes rotated about 45 degrees from a 260 one, so aren't suitable.  240 and 260 may be interchangeable - unconfirmed),
post-42-144023493671.jpgpost-42-144023493668.jpg
Cylinder on the left is a 280zx one, note that it has the mounting holes 45 degrees to the ground, while the 260z on the right has vertical mounting holes.

- Clutch slave cylinder (if it didn't come with the gearbox)
- flexible clutch hose (to go between hard line and slave cylinder, if you get a crappy one a brake place should be able to make a new hose from the sample)
- and either  the metal clutch piping, or a metal rear brake line off a zed (can be reshaped to fit, as i did with mine).

Optional parts (Not required to have a drivable car, but recommended)
- Rear main seal for the engine (there will never be a better time to replace it, mostly as a preventative measure if not leaking, and they are relatively inexpensive)
- Rubber boots to seal transmission tunnel around gear lever against fumes, and a bracket to clamp it down.  You can probably use a generic brand one from Bursons/Repco/Supercheap etc, or spring for the genuine article (which may not fit so well if you have to cut the tunnel for the gearlever, as noted in step 5)
- Pretty gearstick boot (leather, vinyl etc) to cover the rubber boot, or to cover the hole in the floor if you didn't fit a rubber boot!

PROCEDURE:

STEP 1 - Remove tailshaft, then remove auto (DUH!)  Don't forget to undo the torque convertor bolts...

STEP 2 - remove ring gear from back of motor, carefully install spigot bush, after priming with oil (fill centre with oil, squeeze your fingers in on either end until the oil oozes through the porous brass to the outside).  If you chose to replace your rear main seal, do that now.  Then bolt flywheel on - OBSERVE TORQUE SPECS.  Probably wise to have the flywheel machined flat before installing to give a good surface (about $50?)

STEP 3 - Install clutch and pressure plate, making sure clutch plate is properly aligned.  Use a universal clutch aligning tool, old input shaft or my favourite - broom handle with electrical tape around it.  Also make sure that the friction plate goes in the correct way - most will have 'Engine (flywheel) side' or 'Gearbox side' printed on them.  If it doesn't, look and see which way will not allow the friction surface to make contact with the flywheel - that is the wrong way.  Generally the side of the plate where the centre protrudes more faces the gearbox.

STEP 4 -  Remove speedo drive from the auto, fit to manual box (speedo drives are matched to the diff).  Remove the crossmember from under the auto, and fit it to your gearbox.  While you're at it, join the two wires together which prevent the car being started in anything other than park and neutral, otherwise the starter motor won't work when you are finished.  Make sure you get the correct wires, there should be some for the reverse lights as well (which you don't bridge, simply refit to reverse light switch)

STEP 5 - Install gearbox.  With the auto crossmember, it should line up fine.  2 notes here about 280zx boxes, if you use one: 1, The bellhousing bolts need to be longer (Ie: get manual 280zx bellhousing bolts).  2, The transmission tunnel hole needs to be trimmed between 10 and 50 mm at the front edge. 

Install tailshaft.  Should fit easily.

STEP 6 - Unbolt and remove the cover plate over the clutch master cylinder hole (on passengers side of brake booster).  Bolt clutch master cylinder in place.
post-42-144023493668.jpg
Master cylinder in position.


Remove the auto brake pedal (bolt (same as A) at top of pedal, and a pin with a clip (same as C) on the pushrod from the brake booster) YOU SHOULD NOT NEED TO REMOVE THE WHOLE PEDAL BOX, as the manual and auto use the same pedal box, just loaded with different pedals.  Definitely the case in a late 260, and should hold true for early 260 and 240 (confirmation would be appreciated for the latter two).  Install manual brake pedal (reverse procedure)

post-42-144023493769.jpg
View of pedal box loaded with manual pedals with no dashboard covering it! A is the retaining bolt (pivot point), B is the return spring, C is the pin which connects to the clutch master cylinder pushrod.

Install the clutch pedal, using the other retaining bolt you got, along with spring and bushes.  Fit the pin to connect the clutch master pushrod to the clutch pedal. 
Install clutch slave cylinder if it wasn't already fitted to gearbox (Note, bleed nipple must be at the top, otherwise it'll never bleed up).  Install hard clutch line (or shape and fit your rear brake line).  See note 2 at this point.  Fit flexible hose between clutch pipe and slave cylinder.

post-42-144023493672.jpg
Image showing clutch master cylinder at top, with hard line running down to the flexible hose which is bolted into the slave cylinder at the bottom of the picture.

Fill with fluid, crack bleed nipple on slave cylinder and wait till fluid starts to run out (hopefully it should run after a couple of drips).  Bleed with the help of someone else.

STEP 7 - Check everything is tight, check the clutch freeplay, then start car in neutral, push clutch pedal in and carefully attempt to engage gear. 

And that is your manual conversion from start to finish.  About a days work if you are mechanically minded and have all the bits when you start.

NOTES: (will update if and when necessary)
1. With the speedo drive gear swap, you may need to knock the pin out of the gears, and actually swap the cogs themselves over - as in fit the auto gear onto your manual speedo drive gear housing, and fit it into the gearbox.

2. If fluid fails to start running out of the slave cylinder bleed nipple, there are a couple of things to try.  First, try to avoid having your metal clutch pipe running higher than the master cylinder bore at any point, and also avoid having it go up then down.  When you follow the line from master to slave, it should always be getting closer and closer to the ground.  Any higher point (especially higher than the master cylinder) can potentially trap air.  Second, get a syringe with some tubing or a vacuum bleeding kit, and try sucking the fluid through from the nipple.  I have managed to bleed some of the most troublesome clutch lines ever using an old syringe of about 100cc capacity, and heaving on the back end of it to suck the fluid through, and then only got an assistant to bleed with to double-check.


Edited by gav240z, 07 November 2015 - 03:20 PM.
Fix broken image references.


#2 gav240z

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Posted 24 January 2008 - 07:18 PM

Sticky!!!

Thanks for that. I'm sure it will help many of our members. Don't suppose you have any photo's of the process? I know I'm asking a bit here :).

#3 Zeddophile

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Posted 25 January 2008 - 05:47 PM

Nothing useful, no.... Just one of my mates humping a thrust bearing..... (don't ask)

I'll have a look sometime anyways, might be able to find something....

#4 HELLFIRE!

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Posted 26 January 2008 - 12:26 AM

This is awesome!

I would assume that if you had a donor car with a manual setup ready to swap, then this would be easier.

Would it be a good idea to change diffs or did I miss something. I only ask this because I read somewhere that the ratios for an auto are different to a manual.

#5 Zeddophile

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Posted 26 January 2008 - 11:04 AM

Changing diffs is entirely up to you - the auto ratio is usually 3.54, where a manual has something more like 3.7 or 3.9 (can't remember which).

If you have a fairly well powered engine, you may find you like the auto ratio anyway.  I have a range rover with a torquey motor in it, and it still has the 3.5 diffs in on 32 inch tyres (accepted ratio to return to standard gearing with that tyre size is 4.11).  I actually really like the gearing as it is, and don't want to change it, as first gear is actually usable for more than half a second, and second gear runs out to 80km/h, yet the thing still accelerates hard enough to keep in front of WB v8 utes off the lights (that was due to a longer second gear  ;D).  Not bad for a 2 ton 4WD.  I've also had a car trailer and car on the back weighing in at a bit over a ton, and I could barely feel it until I tried to really nail it - cruising off from the lights there was no change in power.

If I was to change the gearing, I definitely wouldn't go to 4.11s, makes the gears way too short.  I'd probably change the transfer case high range gear from 1.2 to 1.4, and only because its a little ridiculous to be able to reach 130km/h in 3rd gear in a large 4WD.  But then again, in 4th up a hill it happily pulls away from 80km, so why waste the time?

#6 sco_aus

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Posted 26 January 2008 - 02:54 PM

I have a 3.7 and 350hp approx with a RB25 gearbox.  The 3.7 is great as it reduces the need for throttle control coming on boost and I can concentrate on other things, but for a lower powered car I would refer a 3.9 or 4.1.  I am still tempted to try out a 3.9, but I cant justify paying around $1k for 2 gears.

#7 Zedman240®

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Posted 26 January 2008 - 03:29 PM

I have a 4.375 in the Z now and it is way to tall for anything except drag racing or hill climbs! The best all round diff I found was a 3.9. Was good at Phillip island and OK for Winton. A 3.5 with a manual trans would be good for an interstate drive or similar. But for quick accelaration, 3.5 you would be struggling....

#8 Zeddophile

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Posted 26 January 2008 - 10:14 PM

I have a 4.375 in the Z now and it is way to tall for anything except drag racing or hill climbs! The best all round diff I found was a 3.9. Was good at Phillip island and OK for Winton. A 3.5 with a manual trans would be good for an interstate drive or similar. But for quick accelaration, 3.5 you would be struggling....


If you're talking track use, then everything I posted before goes out the window - I have a 4.1 diff (factory) in my Alfa, and wouldn't want it any lower, for both reasons of the torque available and the nature of the car.  That said, first gear is useless (Instantly revs out, no actual acceleration), and second now goes to just short of 100km/h (due to the quad throttles allowing it to rev out further than buggered twin dellortos).  Partly due to a bit of a gap in the gearbox ratios, but still.

I have a 3.7 and 350hp approx with a RB25 gearbox.  The 3.7 is great as it reduces the need for throttle control coming on boost and I can concentrate on other things, but for a lower powered car I would refer a 3.9 or 4.1.  I am still tempted to try out a 3.9, but I cant justify paying around $1k for 2 gears.


I think perhaps with a boosted car you probably want a higher ratio for a bit more poke off boost, but if you have sufficient low down torque, you tend to find a lower ratio a bit better - seems a lot of the V8 guys run 3.3 and sometimes even lower diffs for (I'm guessing) this reason.  IMO the amount of torque and its curve is one of the two main factors in picking diff ratios.  The other obviously being how you want the thing to drive.

I find that my Range rover is really comfortable to drive, because the gears aren't short, but it has enough torque that it doesn't matter.  If I shift every gear at 2200 with about half throttle acceleration, I can still get to 80km/h before every other car at the lights.  And thats nice when you're still waking up in the morning, not to have to rev crap out of the thing to stay ahead of the stream, just getting a silky smooth delivery of power.  Thats what happens with a 4.6 litre V8 and towing cam though.

I guess the point I was really trying to make is don't just go straight to chucking a different diff ratio in it because it has an auto 3.54 - drive it first, and then decide.  Everybody is different, and likes a different drive and a different looking car, so don't go spending up on a diff that you may not even want in the end.  You can always change the diff later, its not like you pull the diff out to change the gearbox, so the job will be the same later.  After all, you may go and put a 3.7 diff in, because that was in the manual car, and thats what someone else has, and then find that you'd actually rather a 4.1.

#9 HELLFIRE!

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Posted 27 January 2008 - 12:51 AM


I guess the point I was really trying to make is don't just go straight to chucking a different diff ratio in it because it has an auto 3.54 - drive it first, and then decide.  Everybody is different, and likes a different drive and a different looking car, so don't go spending up on a diff that you may not even want in the end.  You can always change the diff later, its not like you pull the diff out to change the gearbox, so the job will be the same later.  After all, you may go and put a 3.7 diff in, because that was in the manual car, and thats what someone else has, and then find that you'd actually rather a 4.1.


Thank you. I should check what diff I have in my manual daily driver, She is a 5 spd and in 5th will sit on 100 at aprox 2500 rpm. I like this set up but I don't do a lot of stop start city driving.

#10 Zeddophile

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Posted 27 January 2008 - 08:54 AM

Thank you. I should check what diff I have in my manual daily driver, She is a 5 spd and in 5th will sit on 100 at aprox 2500 rpm. I like this set up but I don't do a lot of stop start city driving.


Check this site out: http://www.spannerfo...orts-ratios.php

Just start with the 3.7 diff ratio, fill in the other fields and see what speed it gives you, then play with the others.  Remember, as it tells you down the bottom, tyre size is diameter in millimetres - if you can't be bothered working that out, go here: http://www.miata.net...e/tirecalc.html

#11 Zeddophile

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Posted 04 August 2008 - 08:09 PM

Photo dump - Thanks StevoGJ.

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#12 stevo_gj

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Posted 04 August 2008 - 08:54 PM

No problem mate, happy to have been able to contribute.

Just a couple quick notes:

280zx pedals are the wrong shape for the 260 pedal box.

280zx pedal boxes have the same issue with the bolt holes being rotated 45 degrees as the 280zx master cylinders do, so you cannot simply swap the whole box without drilling a few holes in your firewall.

#13 Lurch ™

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Posted 04 August 2008 - 09:05 PM

Excellent write-up Zeddophile! Should help me when I start the next project...

And thanks for the credit!


#14 Zeddophile

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Posted 04 August 2008 - 09:07 PM

Thanks guys!  Still reworking it a bit more, need to check something with Stevo, and every time I read it again I think of some more to add.

Hopefully someone will convert a 240 soon, and answer a few of the things I'm not sure about!

*EDIT*  Hmmm, just found an absolute gold photo of the pedal box in my archives!

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#15 Hunter

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Posted 09 August 2008 - 03:51 PM

good write up, If I EVER buy an auto I will use this no questions......lol

#16 rollover_610sss

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Posted 22 February 2009 - 06:32 PM

For those interested, i have discovered a cheaper way to convert to manual pedal box and that is to get a second brake pedal (mine came from a 260C wagon) and install it in the place where the clutch pedal should be, all you have to do is trim the pedals to the desired size, i used the rubber pedal covers from a 180b and it looks great, i tried using the 180b pedals but they are too short. its so much easier than pulling the dash apart to remove the pedal box and then lashing out $200 for a clutch pedal, seems like a waste of time to me. nice 'how to'

#17 sexual_sushi

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Posted 13 June 2009 - 06:16 PM

Steve and I were working on his car today and we noticed that the kick down switch (next to the pedal box in the cabin) was restricting movement of the accelerator. With it removed the butterfly valve in the carby now opens fully. It was restricting it by about 10-20 degrees. Maybe this could be added to the tutorial?

#18 Zeddophile

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Posted 13 June 2009 - 07:42 PM

its so much easier than pulling the dash apart to remove the pedal box and then lashing out $200 for a clutch pedal, seems like a waste of time to me. nice 'how to'


As is noted in capital letters in the how-to during step 6. 

As far as the pedals go, I have suspected for ages you could probably use 260z auto brake pedals in the same way (with the sides of the foot pad cut off), but haven't got any zed pedals accessible to check the theory.

Steve and I were working on his car today and we noticed that the kick down switch (next to the pedal box in the cabin) was restricting movement of the accelerator. With it removed the butterfly valve in the carby now opens fully. It was restricting it by about 10-20 degrees. Maybe this could be added to the tutorial?


Kick down switch?  I don't remember the zed having any electric controls over the auto, usually autos of that era just have a cable... Besides which, if its there from standard, it shouldn't be preventing full throttle anyway, unless the linkages to the carby are worn?

#19 Lurch ™

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Posted 13 June 2009 - 09:45 PM

I looked at that when I added the Clutch pedal to my (orig. auto) Zed.
The auto brake pedal is straight, whereas the clutch pedal has a dog leg in it.

Just cutting down the pad area on the auto brake pedal to make fit wont work as it still fowls on the manual brake pedal.
The auto brake pedal would need modifying to make it fit correctly.

#20 Zeddophile

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Posted 14 June 2009 - 11:47 AM

Just cutting down the pad area on the auto brake pedal to make fit wont work as it still fowls on the manual brake pedal.
The auto brake pedal would need modifying to make it fit correctly.


And I'm guessing if you were to bend a dog leg into the auto pedal it would end up being too short?




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