HOW TO: 6 Speed Transmission Rebuild
This is a 6 speed rebuild walkthrough, but the 5 speed is similar. I will be covering internal transmission parts found in the EP3, DC5, FG2/FA5, and ITR/CTR. There will be pix and descriptions of parts in good and poor condition, so you the end user can with confidence identify and replace them.
This is a big writeup so it will take a little time to complete. Bear with me folks!
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This is an in car positioned and labelled diagram to assist overall identification.
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Transmission lingo.
Synchro hub...
Synchro hub+sleeve...
Synchro triple cone...
Distance collar...
Distance collar...
Needle bearings...
Mainshaft assy...
Countershaft assy...
Gear/sync pack...
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General assembly info.
To simplify for the person that has never cracked open a K trans...
The mainshaft has 1st, reverse, and 2nd machined into the shaft. 3rd and 4th are assembled as a pack, 5th and 6th are assembled as a pack, and spin freely on needle bearings.
The countershaft has 1st and 2nd assembled as a pack, and spin freely on needle bearings. The 1/2 countershaft synchro sleeve is also the reverse gear. 3rd through 6th are press on splined gears.
A synchro hub is splined to the mainshaft/countershaft so it spins with the shaft, and has a triple cone synchro and gear on each side...
The shift fork moves the synchro sleeve up or down, locking the synchro hub to the chosen gear. The synchro cones aid in alignment of the hub and gear, so more cones equal smoother/faster engagement.
Main parts of a synchro triple cone...
Notice position of the three tangs...
Notice interlocking of cones 1 and 3...
Notice position of synchro spring ring...
It is important to notice the placement of the three tangs of cone 2 into ALL gears...
It is important to liberally lube all contact surfaces. Honda suggests MTF, i used Mobil1 0w30...
It will help to mark the synchro hub and sleeve assembly with a sharpie. The hub has 6 deeper grooves that fit 6 taller teeth on the sleeve. This is the case FOR ALL THREE synchro hubs and it is IMPORTANT to have this assembled correctly...
It is important to notice the positioning of this tang on the 3rd synchro sleeve, and its relation to the 3rd synchro hub...
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Some of the BAD you may find in your teardown.
ITR 2nd...
ITR sleeve...
ITR hub...
ITR synchro...
Its kinda hard to see, but there is a ton of metal flake in this crap. This was flushed/scrubbed out of the center of the mainshaft. The countershaft was just as bad. PB Blaster and a wire handle bottle/block brush are your friends here...
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Parts interchangeability.
Colin on k20a spent some time in PM's with me and said one simple thing... parts can interchange in their same group, not up and down the shaft. This is mostly true... (and thanks for all the time you took as well).
For instance, the synchro hub for gear pack 1/2 (countershaft) cant be used for gear pack 3/4 or 5/6 (mainshaft). The 1/2 hub OD/ID spline is larger, and the hub thicker. More to add...
The synchro hub and sleeve for gear pack 3/4 are special and cannot be flipped. This is what you will most likely end up buying a complete gearset of if you have 3/4 issues. More to add...
The synchro hub for gearpack 5/6 interchanges between all synchro triple cone K transmissions. The synchro sleeve for gearpack 5/6 is different between the 6 speed and the 5 speed model. The 5 speed sleeve CAN be used in a 6 speed synchro triple cone setup, but you wont be able to rip it into 6th. The design of the sleeve will allow fast downshifting to 5th, but not into 6th. More to add...
Synchro spring rings are interchangeable. 1/2 gear pack spring rings are larger than 3/4 or 5/6 gear pack spring rings. 3/4 and 5/6 spring rings are interchangeable. They interchange between other K trannies in this manner. More to add...
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When its all said and done.
This is your goal...
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