Gearbox strip and rebuild.

[enzo]

Just spent a bit of time stripping and rebuilding a gearbox to replace the bearings. I took a load of photos whilst I was at it, so thought I'd do a bit of a write up.

First:-

Remove this.

There is another on the other side of the casing, and behind these, are these springs and plungers. The long spring and steel ball are located in the casing under the gasket you can see in the first pic.

Passenger side.


Driver side.

The roll pin in the previous pic is knocked out of here with a punch.



Next, remove these bolts around the rear casing.

You can then tap the rear casing off, to reveal the rear of the mainshaft.



This box has lived outside for about 3yrs under no cover, that's why it's as rusty as it is.

Next, into the bell housing.

Remove these bolts from the front cover.

Remove the cover and you'll see the input shaft and countershaft front bearings.

Remove this snap ring from the input shaft front bearing (the larger one).

You can then remove the bell housing from the gear cluster assembly, leaving you with this.






Bedtime now. I'll carry on tomorrow.

[enzo]

Carrying on then:-


Remove selector fork roll pins. The one with the punch is 3rd/4th. The other selector is for 1st/2nd.


This one is 5th/reverse.




Remove these bolts from adaptor plate. Behind these, are the detent balls and springs, and a roller, all shown in the next pic with the selector roll pins.


Detent balls and springs.


You can then remove the selector forks and rods


Slight problem with 5th/reverse.


Mounted onto a steel plate so I could hold it in a workmate.



Starting to strip the cluster.


Remove the counter shaft front bearing.
Behind this, remove the circlip and sub-gear assembly, which is just a shim, a collar and a thin plate gear.


Sub gear assembly.


Remove the counter shaft front gear. The pinion shaft will come off with it.



Moving to rear side.


Speedo drive gear, and mainshaft rear bearing.
Remove circlip, drive gear and steel ball, and second circlip.
Remove third circlip by the bearing.


Draw off rear bearing, and remove fourth circlip.

[superclarkey]

Nice strip down mate, but i wouldn't bother putting that back together if it was me lol, proper rusty.

[enzo]

Nice strip down mate, but i wouldn't bother putting that back together if it was me lol, proper rusty.

Lol, bit of a story with this. I'd already stripped the gearbox which I've rebuilt, and it's in much, much better condition than this one. But I never took any photos.
So the stripdown is this scrap box, and the rebuild is on another.
I love doing a job twice.

[Actual_Ben_Taylor]

Great writeup

[enzo]

Remove mainshaft and countershaft locknuts. They are staked to the shafts, and the mainshaft nut is LH thread. Remove thrust washer and roller bearing from mainshaft.


Locknuts, thrust washers roller bearing.


Remove 5th counter gear, followed by reverse counter gear and spacer.





Remove this circlip, followed by reverse idler thrust washer, gear and roller bearing.




All components from rear side.


Press shafts out of adaptor plate. This will remove a bush, 5th and reverse main gears, synchro hub and needle roller bearings from mainshaft.

[5imon]

Great write up, keep up the good work.


Could this be made into a sticky please, very helpful and useful info

I didnt have a clue the first time I cracked open a SR20 box, on my 8th now lol

[enzo]

Great write up, keep up the good work.


Could this be made into a sticky please, very helpful and useful info

I didnt have a clue the first time I cracked open a SR20 box, on my 8th now lol

Lol, 8th box, are they that weak?

[Silane]

Great thread. I was thinking it doesn't look *too* bad, as long as you remember where everything goes.

[5imon]

Lol, 8th box, are they that weak?

haha no this was over 7 200sx's and I like to make sure the insides are in good condition before fitting.

but the selectors are very weak indeed.

[DavS1RST]

Nice write up, i've never saw a RWD box bein taken to bits, only FWD....Looks like some job, I'd never remember what bits go where

[tom_rosenback]

Real great writeup! Good to have this if/when the box says up it´s contract

[enzo]

It's great to see people appreciate it, nice one.

Time to continue then.


When the shafts are out, remove the thrust washer and steel ball.



1st gear, needle roller bearing and bush will then lift off. If you have the same luck as me, the coupling sleeve, brass baulk ring and all the inserts will end up all over the garage floor




You can then press the 2nd gear assembly off the shaft.
It seems enzo forgot to take an exploded pic of the assembly.


Press 3rd gear assembly off the front of the shaft.




Draw off counter shaft rear bearing.
The shafts are now dis-assembled, I just removed the input shaft bearing, but there's no pic of that.


Remove the screws in the bearing retaining plate.
Remove the reverse idler shaft.




Press out the bearing.
All stripped down now, I'll post the rebuild later.

[Aj82]

Great work mate and very helpful to many folk!
Iv had the same issue with the baulk rings on VW's! Hate that feeling!! lol


Cheers Aj

[DLowe]

this came in very handy today for me, I have just got the box of and removed the bell housing folowing this guide

will see what the problem waas tomorrow, and look forward to the rebuild thread

[Bubble]

What a great thread

I have just had my GTT box rebuilt and now I know what sort of a job they had to do.

[enzo]

Starting the rebuild then.


Pressing new bearings into the adaptor plate.
All the new bearings, are open type, ie no seals or grease. The old ones were sealed.


Fit the reverse idler shaft and bearing retainer. The six screws are staked at a couple of points

Onto the mainshaft components.

Replace the 2nd gear assembly on to the mainshaft. No pic, but this has to be pressed on.
Assemble the coupling sleeve, inserts and baulk ring and replace over the hub. The large chamfer on the coupling sleeve has to be towards the rear of the box.
Finally slide on 1st gear.




Replace steel ball, and thrust washer.


Press mainshaft into main bearing.


Followed by the countershaft.


Press 3rd gear assembly onto mainshaft.




Followed by thrust washer and circlip.

[enzo]

Pressing new bearing onto input shaft, again an open type rather than sealed.
Replace input shaft onto 3rd gear assembly on mainshaft, as in next pic.


Press counter shaft drive gear onto counter shaft.


Followed by the sub-gear assembly in the order, thin plate gear, shim, collar then circlip.


Press counter shaft front bearing on.

[enzo]

Carrying on with the rebuild,


Replace the reverse idler gear components, BUT


Don't replace it like I did at first.
The machined grooves across the face of the gear should be towards the plate, not as they are here. I've changed it now.


Next it's the reverse gear onto the mainshaft


Followed by the coupling sleeve and 5th gear.


Then the roller, thrust washer and roller bearing.




Finally the locking nut.

[enzo]

Replace counter shaft components.
Spacer, counter reverse gear, counter 5th gear, rear bearing and locknut.




Torque counter shaft lock nut.


Replace mainshaft rear bearing and speedo drive gear.