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How to: Strip C series gearbox

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#1 Trevstar



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Posted 04 September 2017 - 09:17 PM

Seeing as photobucket has fucked us all over and taken away many valuable pics

Calum122 mentioned I should take pics and document for the rest of you (which I should have just done to begin with!)

First thing is I found this video very helpful so I suggest you check it out to get an idea of what you're getting into


C series gearbox's are all similar in one way or another, to us we most commonly use the C52, C56 and the C150 (for the non turbo users)

If you're planning in fitting a LSD then you will need to know what type of ring gear you have inside your box, it will be either a 8 or a 6 bolt from what I understand,and you won't necessarily know until it's apart.

You won't need to strip the entire gearbox to change the diff. You'll only need to strip it completely if you're replacing synchros or broken gears

LSD types (for the record I'm not a gearbox expert!)

Helical, such as Quaife ATB or TRD helical (extremely rare af), for those that don't know these work, they work basically by gears inside the LSD to distribute torque. As Morgey told me, these LSDs are best suited for road use as low noise (if any), doesn't have harsh engagement and doesn't require maintenance however it doesn't lock 100% (but this isn't a concern for road use)

Mechanical/clutch type, such as TRD mechanical, kaaz, Cusco etc., these work by having a number of clutch plates inside that lock both wheels to about the same speed, best suited for the track as they are stronger lock, most can have adjustable preload and selectable between 1.5 & 2 way (note: always use 1.5 way on FWD vehicles, 1 & 2 way will cause adverse affects). These LSDs on the other hand are noisy and knock when turning, can sometimes have harsh engagement, require regular gearbox oil changes, oil with friction modifiers, and eventually the clutch plates will need replacement, and if you use these on the road then they will wear out more quickly every time you go round a corner


Assuming you have your gearbox removed, remove everything else attached to the box like clutch cylinder, brackets, everything and drained as much oil as possible. You will need to remove all the bolts mating the two cases together, make sure you have decent sockets and use wd-40 where you can because the bolts can be stubborn. Don't want to round them and have to drill them out

- Remove the 3 bolts [in Violet] inside the bell housing


- Then remove all the bolts [in green] around the bell housing, there is more you can't see in the picture but should be obvious


- Take out the bolt for the speedo drive, it's just the one bolt and a little plate securing it in place then just pull out the speedo with a bit of force if necessary


- Remove the the Allen head cap [in green], there is a spring underneath so keep pressure on it til it's completely undone and remove the spring and retainer, there is a ball bearing in there too but you can try to get it out with a small magnet, or it will fall out the from the inside when you move the box around, so just keep an eye out when you completely separate the cases

Only undo the other Allen head cap [in red] a bit, you don't really need to take it out

If you're just doing the LSD don't worry about the red bolt


- With a mallet or hammer wrapped in a cloth, tap around the edges to split the cases, after a few taps the sealant will break loose and the cases will go but not all the way, it should separate about an inch or so (note the light blue dot to know where to look in the next step)


- Then inside the box, in the gap, you'll notice the cases won't completely separate due to reverse selector arm being the bolted to bell housing side. This is a fiddly part as you will need to remove the 2 bolts [in Violet] holding the selector arm in place (note the light blue dot to know where to look)


- Once the bolts are removed you will then be able to giggle the bell housing case about a little, maybe a another tap or two, and it will come apart, at this point you will be able to remove the differential


*If the LSD is all you are doing then just swap over the ring gear and go back from this point to reassemble*

[Don't forget to replace the bearings and the races, clean the magnet inside the case and apply the sealant to the mating surfaces before reassembly. To reinstall the 2 bolts for the reverse selector arm, make sure it's in the correct place. It should connect to the selector fork and in the groove on the reverse gear, then lower the other case down onto it and hold one bolt with some long needle nose pliers (thin enough to fit in the gap) and hold the bolt and get a ratchet spanner to get it started on the thread, but before you screw it in all the way in, do the other one so you don't waste your time doing one up, dropping the other and having to take it apart again. Again this will be fiddly. Reapply any sealant you may have smudged during this process]
Also Morgey has added a comment below, is worth taking note also about shimming the differential

if you are stripping the entire box then continue on

- You'll need to remove the back cover, remove the bolts in red


- Undo the gearbox oil filler bolt [in green] but again this doesn't have to be completely removed. Then remove the bolts for the selector [in red], this might need a few taps around the edges to break free, this will also need a gasket replacing or alternatively you can silicone on reassembly


- next you'll need to undo these 2 Allen head caps [red], same as the one before keep pressure on them until they are all the way out as there is a spring underneath and a retainer, and again there are ball bearings in there so you can try to get them out with a small magnet or try and wiggle the box around to get them out


- Remove this bolt [green] from the selector fork (this is a special bolt, don't loose it!)


-Then this rod will fall out the bottom [orange], there is two smaller ball bearing in the dark gray arm attached to the rod, remove these before you lose them


- Now you can slide off the selector fork off the gear [blue], then you can remove the 5 bolts [green] holding on the plate below the gears


- Then pull off the gear the fork was attached too


- There is a circlip that you will need to take off the shaft, you will be able to knock this off with a flat head screw driver quite easily


- Turning you attention to the other shaft, there is a nut that has a tab bent into a notch to prevent it coming undone, knock a flat head into the notch and bend the tab out so you can remove it (note, try to avoid jamming a screwdriver or any in the teeth of the gears to prevent them from spinning as you will chip them *INSERT MEATHOD)


- Take one of the casing bolts and place it in the hole in the top of the shaft then use a 3 inch, 3 leg gear puller to pull off the gear from the shaft

The purpose of the bolt is so that you don't damage the shaft in any way, and preferably don't use a gear puller on the piss like mine is, might also be a good idea to mark the top side of the gear


- Now you can simply slide off the brass synchromesh gear and the 5th gear

You may notice in this picture that the synchro teeth on the 5th gear are a little worn, if this is excessively worn will cause you to pop out of 5th gear and/or crunch, but this gear is about £110 (120 euro) from toyota


- Remove the 2 half moon needle bearings, check the condition of these, they don't often fail but if they do they are like £35


For the next part you need to use a gear puller again but you need to make sure it fits in the groove, as you can see below, the gear puller I used previously won't fit in the groove so I have had to order another one that fits. If you have a spare puller or just don't really care then you could try to grind the claws down to fit but they need to be even but it may also increase the chances of the puller breaking


- So I received my gear puller, this is the type you will need, I would probably recommend buying a extra long version of this if you can, so it can reach further down the shaft (oi oi..) for later on


- Put the legs in the grooves and wind it down. Don't use a impact gun on this otherwise the impact motion will make it slip, better to use just a ratchet or spanner


Now you might notice it's quite tight and starts spinning. To keep it in place, grab the nut and put it on so it's only just starts on the thread and get a screw driver and place it like so, to keep it in place while you pull the gear off


- Once the gear is off, you can remove the plate


- Plate removed, there is two large retaining circlips that you need to remove


-Now they're out, the gears should drop down and you will be able to take out the output shaft


- Before you can remove the input shaft you'll need to remove the reverse gear, to do this you need to take out this bolt [GREEN]


- Then you will be able to slide out the reverse gear and the rod it slides on


- Now you can remove the input shaft


-Now the box should be empty



-Starting with the input shaft, there is a spacer and yet another circlip above the bearing, obviously you're going to have to remove this


-Then you will need to use the gear puller again and put the legs just under the gear below the bearing, again you do not want this to slip or you'll break the teeth!! So don't use an impact gun, do this carefully and slowly with a ratchet or spanner. Be sure to keep an eye on everything to be sure the puller is going on straight


-Once off there is some more needle bearings inside the gear


-Once again there's another spacer and a circlip, remove these


-This is where I mentioned earlier about getting a longer gear puller, this would be the proper way to do this

However, I was impatient because I didn't want to buy and wait for yet another gear puller to arrive, so the poor man's way is to turn the shaft around and get a flat head screw driver (widest you can get), and GENTLY tap with a mallet or hammer on these 3 locating sections (or whatever they're called)

-Tap a few times then swap to the next one to avoid breaking


-Then there you go! That's the input shaft stripped



Edited by Trevstar, 11 September 2017 - 10:39 PM.

I don't suffer from turbo lag... because I don't have a turbo.

R.I.P Shahid Moghal
2/10/94 - 14/10/16

#2 Starlet__SR


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Posted 04 September 2017 - 09:36 PM


#3 maddox710


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Posted 05 September 2017 - 06:37 AM

Well done dude nice work

#4 morgey


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Posted 05 September 2017 - 08:20 AM

I will add, when changing diffs, you should really reshim the diff bearings or at least check them, this is quite a long winded process as involves closing and reopening the box a few times and measuring with shim the clearance between the box and the bearing casing in the driveshaft holes, I know not many people bother doing this (myself included) but this can prolong the life of diff bearings and stop any droning.

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