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.

http://i1140.photobucket.com/albums/...pscam011tu.png

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Transmission lingo.

Synchro hub...

http://i1140.photobucket.com/albums/...ket_35569_.jpg

Synchro hub+sleeve...

http://i1140.photobucket.com/albums/...ket_35663_.jpg

Synchro triple cone...

http://i1140.photobucket.com/albums/...ket_35653_.jpg

Distance collar...

http://i1140.photobucket.com/albums/...ket_35562_.jpg

Distance collar...

http://i1140.photobucket.com/albums/...ket_35561_.jpg

Needle bearings...

http://i1140.photobucket.com/albums/...ket_35570_.jpg

Mainshaft assy...

http://i1140.photobucket.com/albums/...ket_45289_.jpg

Countershaft assy...

http://i1140.photobucket.com/albums/...ket_34230_.jpg

Gear/sync pack...

http://i1140.photobucket.com/albums/...ket_35554_.jpg

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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...

http://i1140.photobucket.com/albums/...ket_35554_.jpg

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...

http://i1140.photobucket.com/albums/...ket_35654_.jpg

http://i1140.photobucket.com/albums/...ket_35656_.jpg

Notice position of the three tangs...

http://i1140.photobucket.com/albums/...ket_35657_.jpg

Notice interlocking of cones 1 and 3...

http://i1140.photobucket.com/albums/...ket_35659_.jpg

Notice position of synchro spring ring...

http://i1140.photobucket.com/albums/...ket_35661_.jpg

It is important to notice the placement of the three tangs of cone 2 into ALL gears...

http://i1140.photobucket.com/albums/...ket_35553_.jpg

It is important to liberally lube all contact surfaces. Honda suggests MTF, i used Mobil1 0w30...

http://i1140.photobucket.com/albums/...ket_35542_.jpg

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...

http://i1140.photobucket.com/albums/...ket_35560_.jpg

http://i1140.photobucket.com/albums/...ket_35558_.jpg

http://i1140.photobucket.com/albums/...ket_35552_.jpg

It is important to notice the positioning of this tang on the 3rd synchro sleeve, and its relation to the 3rd synchro hub...

http://i1140.photobucket.com/albums/...ket_35556_.jpg

http://i1140.photobucket.com/albums/...ket_35557_.jpg

http://i1140.photobucket.com/albums/...ket_35550_.jpg

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Some of the BAD you may find in your teardown.

ITR 2nd...

http://i1140.photobucket.com/albums/...ket_35564_.jpg

ITR sleeve...

http://i1140.photobucket.com/albums/...ket_35565_.jpg

ITR hub...

http://i1140.photobucket.com/albums/...ket_35571_.jpg

ITR synchro...

http://i1140.photobucket.com/albums/...ket_35567_.jpg

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...

http://i1140.photobucket.com/albums/...ket_35682_.jpg


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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...

http://i1140.photobucket.com/albums/...-56-41_473.jpg

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Assembly with specs.

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Mainshaft.

Before disassembly, measure the depth of the inner bearing race to the end of the mainshaft. Measure it in three places, take the average of all three (if applicable), and record for later comparison.

http://i1140.photobucket.com/albums/...psfm3bhiqa.jpg

This will help you calculate tolerance variance after reassembly, and if your before and after measurements are identical (or there is no shim combination available from Honda to accurately take up the variance) you do not have to mock the mainshaft in the trans case to check for shim clearance per the manual (shims retain the oil plate, remove with snap ring pliers). Just use your previous cone washer (recommend replace) and shim (1mm) at the bottom of the mainshaft, and reuse upper bearing shim(s).

http://i1140.photobucket.com/albums/...ket_45290_.jpg

Needle bearing...

http://i1140.photobucket.com/albums/...ket_45291_.jpg

3rd gear (23.92-23.97mm)...

http://i1140.photobucket.com/albums/...ket_45292_.jpg

Synchro triple cone assy...

http://i1140.photobucket.com/albums/...ket_45293_.jpg

3/4 synchro hub+sleeve (use press to gently push hub into position)...

http://i1140.photobucket.com/albums/...ket_35550_.jpg

http://i1140.photobucket.com/albums/...ket_35551_.jpg

http://i1140.photobucket.com/albums/...ket_35552_.jpg

Synchro triple cone assy...

http://i1140.photobucket.com/albums/...ket_45294_.jpg

4th gear (23.92-23.97mm)...

http://i1140.photobucket.com/albums/...ket_35549_.jpg

Needle bearing...

http://i1140.photobucket.com/albums/...ket_35547_.jpg

Distance collar (24.03-24.08mm x 2)...

http://i1140.photobucket.com/albums/...ket_35546_.jpg

http://i1140.photobucket.com/albums/...ket_35545_.jpg

Needle bearing...

http://i1140.photobucket.com/albums/...ket_45295_.jpg

5th gear (23.92-23.97mm)...

http://i1140.photobucket.com/albums/...ket_35538_.jpg

Synchro triple cone...

http://i1140.photobucket.com/albums/...ket_35537_.jpg

5/6 synchro hub (use press to gently push hub into position)...

http://i1140.photobucket.com/albums/...ket_35536_.jpg

5/6 hub sleeve...

http://i1140.photobucket.com/albums/...ket_35534_.jpg

Synchro triple cone...

http://i1140.photobucket.com/albums/...ket_45296_.jpg

Distance collar (24.03-24.08mm)...

http://i1140.photobucket.com/albums/...ket_35561_.jpg

http://i1140.photobucket.com/albums/...ket_35533_.jpg

Needle bearing...

http://i1140.photobucket.com/albums/...ket_35532_.jpg

6th gear (23.92-23.97mm)...

http://i1140.photobucket.com/albums/...ket_35531_.jpg

NOTES:

1) Consider distance collars as spacers.

2) There is no separate distance collar for 3rd gear, its part of the mainshaft.

3) Since each gear on the mainshaft measures the same thickness, and each distance collar measures the same thickness, it is safe to say the tolerance for the distance collar machined to the mainshaft for 3rd gear should be 24.03-24.08mm.

4) Each synchro hub locks the previous gear(s) in place (spaced by distance collars). For instance, 3/4 gear pack hub locks 3rd gear against the base of 2nd gear machined to the shaft. There will be a measureable wear tolerance between 2nd gear/3rd gear, and between 3rd gear and the 3/4 gear pack hub.

5) 4th and 5th gears are locked between the 3/4 gear pack hub and the 5/6 gear pack hub. There will be a measureable wear tolerance between the 3/4 gear pack hub and 4th gear, and between 5th gear and the 5/6 gear pack hub.

6) The main seal for the mainshaft is under the lower bearing. Depending on mileage or how long the trans has sat without use, this seal should be replaced.

If you dont have a bearing puller, you can rent one from a local Auto Parts chain, or use a heat gun with liberal use on the case around the bearing (at LEAST 5 minutes, the longer the better), turn the case over and tap it with a hammer using a piece of wood to retain case integrity. The bearing will fall out.

Clean (WD40/toothbrush and cleanup with a fresh rag) and lube case/new bearing surfaces. You can also use heat to aid new bearing insertion, but be careful to avoid overheating the new seal. I use a piece of aluminum pie pan cut to bearing size in the hole to help deflect direct heat. Remove aluminum shield before bearing insertion.

7) ALWAYS replace the bearing at the top of the mainshaft.

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Assembly with specs.

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Countershaft.

Before disassembly, measure the depth of the inner bearing race to the end of the countershaft. Measure it in three places, take the average of all three (if applicable), and record for later comparison.

http://i1140.photobucket.com/albums/...psfm3bhiqa.jpg

This will help you calculate tolerance variance after reassembly, and if your before and after measurements are identical (or there is no shim available from Honda to accurately take up the variance) you do not have to mock the countershaft in the trans case to check for shim clearance per the manual.

By nature of design, disassembly/assembly variance here will primarily warn you of assembly issues (gears not pressed on right, wrong synchros used in the 1/2 gear set, worn distance collar/1st or 2nd gear/sync hub surfaces... etc).

http://i1140.photobucket.com/albums/...ket_45206_.jpg

Distance collar...

http://i1140.photobucket.com/albums/...ket_45207_.jpg

Needle bearing...

http://i1140.photobucket.com/albums/...ket_45208_.jpg

First gear...

http://i1140.photobucket.com/albums/...ket_45209_.jpg

Synchro triple cone...

http://i1140.photobucket.com/albums/...ket_45210_.jpg

1/2 synchro hub...

http://i1140.photobucket.com/albums/...ket_45211_.jpg

http://i1140.photobucket.com/albums/...ket_45212_.jpg

http://i1140.photobucket.com/albums/...ket_45213_.jpg

Friction dampner...

http://i1140.photobucket.com/albums/...ket_45215_.jpg

http://i1140.photobucket.com/albums/...ket_45214_.jpg

http://i1140.photobucket.com/albums/...ket_45216_.jpg

Distance collar...

http://i1140.photobucket.com/albums/...ket_45218_.jpg

Synchro triple cone...

http://i1140.photobucket.com/albums/...ket_45219_.jpg

Needle bearing...

http://i1140.photobucket.com/albums/...ket_45220_.jpg

1/2 synchro sleeve/reverse gear...

http://i1140.photobucket.com/albums/...ket_45221_.jpg

2nd gear...

http://i1140.photobucket.com/albums/...ket_45222_.jpg

http://i1140.photobucket.com/albums/...ket_45223_.jpg

3/4 gears...

http://i1140.photobucket.com/albums/...ket_45225_.jpg

Tolerance for 1/2 gearpack...

http://i1140.photobucket.com/albums/...ket_45224_.jpg

5/6 gears...

http://i1140.photobucket.com/albums/...ket_45226_.jpg

Shim+bearing+tolerance...

http://i1140.photobucket.com/albums/...ket_45227_.jpg

NOTES:

1) DO NOT try to push more than two splined gears onto the countershaft at a time. It is BEST to press them on one at a time.

2) Be sure to lubricate the shaft and the splines of the gears to ease installation.

3) 3rd gear holds the 1/2 gearpack together, and only after installing it can you check 1/2 gearpack tolerance.

4) ALWAYS replace the bearing at the top of the countershaft.

5) Heat can also be used to remove/install the lower counter shaft bearing.

6) If all distance collars, the sync hub, and gear contact surfaces meet listed specs and show immeasurable wear, and each pressed on gears contact surface meets spec and are pressed in place properly... there should be no need for a shim change below the upper countershaft bearing.


More to add...

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Countershaft and FD ring gear.

4.7 FD...

http://i1140.photobucket.com/albums/...ket_47409_.jpg

NOTES:

1) The FR ring gear is interchangeable between k differentials.

2) The countershaft MUST follow its matching ring gear. If you want to change your FD from a 4.3 to a 4.7, then you MUST have the ring gear, the countershaft, and the lower countershaft bearing.

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Shift shaft assembly.

Left 6 speed, right 5 speed...

http://i1140.photobucket.com/albums/...-58-52_895.jpg

NOTES:

1) kXXa shift shaft pieces are interchangeable between 5 and 6 speed trans.

2) kXXz shift shaft and assy base are different (following trans case/shift cable changes). Lower kXXz shift shaft parts interchange with kXXa shift shaft parts.

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This is a 5 speed trans shift shaft assy with 6 speed assy parts (deleting the solenoid, but still allowing reverse mechanical lock)...

http://i1140.photobucket.com/albums/...1-34_414-1.jpg

NOTES:

1) It is IMPORTANT to use a moly based grease on the contact surfaces during assembly.

2) It is IMPORTANT to verify correct assembly and operation of the shift shaft assy. Putting the trans together (without sealant) and installing the shift shaft assy (without sealant) will allow you to move through the gears and verify proper working order.

3) When turning the mainshaft by hand, it is normal for the differential to turn WITH THE TRANS OUT OF GEAR.

4) The two springs between the assy base and retaining cup are commonly replaced with MTEC springs.

More to add...

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there any way to get the pics back on this DIY?

Pics are still there, and both of my Photobucket accts are still active. Maybe its on your end? Let me know if i can help.

You are amazing, this guide is very in-depth and it helped me on my transmission build. One thing I'm not exactly sure about is the shimming for the countershaft. When I rebuilt my transmission with Gear-x 1-4, I reused all the shims and washers and didn't check clearances, I just pressed the gears till they reached the end.

..So any chance OP you're still around and can find a new image host for those pix? I may need to do a rebuild soon. :/

Yes im still around. Dont get on too often though. Im not sure why the pics arent up. Ill get on my accts and see what i can find out.

-Dave

Any Luck Getting the pictures Back? I have been looking all over for a guide like this so I hope you can recover the pictures.

Same question here : Can we get the pictures back, at least for a while? Thanks for the post, Ba82Ep3.

The issue isnt EPHatch, or K20a.org either... as i had this thread linked there as well. The problem is with Photobucket. They decided to end free hosting and basically ruined almost every car forum on the planet.

I still have my two Photobucket accounts and have been trying to get my photos off of them, but they only allow you to do it one photo at a time. Im talking thousands of pics here. Time consuming isnt even descriptive enough...

Dangit, that's what happened? Ugh, was wondering what happened to all my posted pics (I used photobucket also). Had to host through ephatch to get anything to show.

Whats going on guys?

I recently tore down the transmission that i used in this thread at the 111,278 mile mark. It needed mainshaft bearings as they were very noisy, so i had all bearings and seals on hand for replacement. I also installed another clutch.

I see Photobucket has allowed the use of some pics. Ill go back on my account and see what i can do to add what i had to finish the thread... and also update this particular transmission after its extensive use and abuse.

- Dave

Hey, Dave,
First off, great write up! Very informative and will definitely be saved as a bookmark.

I'm looking for information about adding the TSX 6th gear to my 02 Si. And looking for recommendations for a final drive, as it is my daily and would like 6thb for the highway speeds. Any help is appreciated.

Thanks,
Patrick

Hey guys. Trans time again for me. 147k miles and second gear needle bearing finally said "no". I'm not even mad... she exceeded her service life in a very harsh environment.

As it's rebuild time I will be documenting the rebuild process and passing on the info to you guys. I'll also link it to k20a.org but I don't know how that page is handling its info anymore... I can't even log in with my original name so.

As we all know the Covid has the world upside down and parts are hard to come by. I have several parts on backorder so check back, but be patient as it will take a while to actually complete the physical rebuild.

This time, I have a large stainless table 6x2 long and will be tearing down two transmissions at the same time, so should be nice comparing my trans in its state with my maintenance schedule to one that isnt/wasn't maintained with far less miles on it.

See yall soon!