h) Tranny Rebuild (April-2010 Complete)

Time to refresh the transmission.  It is the basic 4 speed without overdrive.  I purchased the rebuild kit on-line and began to disassemble the unit.  One web site that was a gold mine of information was the Buckeye Triumphs.


Cleaned up and ready for disassembly

First I removed the “Top Cover” and set it aside (real easy).

Top Cover Removed

Then I removed the Rear Extension and Drive Flange.

Drive Flange

Rear Extension Removal

Next, things started to get more difficult as I needed to remove the Clutch Withdrawl Assembly and as predicted the cross bolt tip had broken off.  I slid the yoke off of the forks to gain access to the Bearing assembly and left the Withdrawl assembly for later. when I would have better access.

Withdrawl assembly in  tact

Below you will see that the Yoke is removed exposing the front end bearing cover which was removed next.

Input Spline with bearing cover in-place

Next I removed the Front End Bearing cover exposing the input shaft bearing.  I then removed the retaining clips and set them aside.  At this point I needed to remove the small cover just to the bottom left of the input shaft (Picture Below).  This exposes the counter-shaft that the counter gear pack spins on.  Also at this time head off to the back end (out-put shaft end) and remove the retaining plate that locks in the Reverse Gear shaft & Counter Shafts (Phillips head screw).  When you drive these shafts in the gears will fall away allowing you to free up the main shaft gear pack.

Countershaft Cover

Reverse Gear & Countershaft retainer

Once the plates are removed (Exposing the ends of the shafts) I tapped out the shaft located on the in-put shaft side until it was removable from the rear.  This allows the counter- gear-pack to fall away from the main gear-pack allowing you to tap out the input shaft bearing.  Using a long screwdriver I was able to tap on the bearing race (from the inside of the case) slowly moving it out.  This will remove the bearing along with the front portion of the main shaft (the Input Shaft)

Input shaft bearing removed

Input shaft bearing with shaft

Next I was able to slide the main bearing pack foreword to expose the output shaft bearing and remove that in the same manner.  Once this is done you can remove the Main-shaft gear pack from the housing along with the other two remaining gear packs (hold or bind the gears together so that they do not slide off of the shaft).

Main Gear Pack

All 3 gear Packs

Now that the Case is empty, I was able to position the Clutch Withdrawl Unit so that I could drill out the broken tip freeing up the Fork for removal.

The case was then cleaned.

Cleaned case ready for paint.

So far, this has been much easier that I expected.  I will plan to take the transmission section at a time completing the main case first, output second and the Shifter Cover (with forks) last.

The rebuild kit consists of Bearings, Syncros, Seals, Counter shaft & Gaskets for the main gear packs (Main Shaft & Counter shaft), what it does not contain are the thrust washers for the counter shaft and I needed to purchase these separately.  I cleaned up all of the gasket surfaces and degreased the entire housing.  Next I installed the new Syncros and the input shaft bearing, when these were all set it was time for re-assembly.  1) Install the Reverse gear & shaft.  2) Using real sticky grease place both of the counter shaft  thrust washers in-place making sure they do not get knocked out of position drop in the counter shaft.  I found it easiest to do this with the transmission housing sitting “Bell housing down”.  Allow the counter shaft to drop all the way to the bottom of the housing, if you do not do this the input shaft will not clear the gears.  3) Place the housing back on it’s side and install the main gear pack (on shaft) into the housing and slide on the output bearing (partially).  4) Install the input shaft assembly and tap into place (completely).  Now, hopefully the thrust washers for the counter shaft did not move too far out of place.  Install the Counter shaft working the shaft carefully thru the assembly and lock it all into place with the cross plate & screw.  Now you can drive the output shaft bearing into place and replace all of the spacers and snap rings.

Counter Shaft & Reverse Gear In-Place

Note that the Counter Shaft is setting at the bottom of the casing to allow clearance for the input shaft.

Input shaft & main Gear Packs in placeNow is the time to secure the Counter shaft into the Counter Gear Pack and secure at both ends.

Reverse Gear & Counter Shaft secured

Input shaft Bearing/Housing and Counter Shaft Cover

Output Shaft Bearing Tapped Into Place.

Secure both the Input shafts & Output Shafts with the proper spacer & circlip

The next Stage in the process is to rebuild the “Top Cover” or shifter assembly.  This was pretty straight foreward.

Before Picture

Greasy old forks

To disassemble, remove the fasteners holding on the 3 forks then remove the 3 screw plugs that allow the shafts to click into place.  Removing the plugs was a little involved as they were aluminum caps pressed into the bores and needed to be drilled out.

Screw Plugs drilled out

The balls will fall thru.  Do Not over drill the holes.  They will be about 10mm in diameter and you will be able to tap them out using a 7/16-20 tap.  Re-installation will be with set screws and the spring force will be properly set.  I needed to shorten the set screws by 30%.

Next the entire unit was cleaned and prepared for re-assembly.  New O-Rings were purchased.

Cleaned & Ready for re-assembly

The first step in reassembly is to slide the 3rd/4th gear shaft into place remembering to reinstall the interlock pin and selector shaft balls.  Next went in the Reverse shaft then finally the 1st/2nd gear shaft.  reinstall the neutral safety switch & reverse light switch to help retain the balls & cross Pin.  Secure the forks with the proper retaining screw/pins then reinstall the Spring loaded pin & balls for the shafts.


The assembly was completed with greasing all of the sliding / moving parts.  Now it is ready to bolt back onto the gearbox.

Almost Complete. Tested OK

Next will be the Refresh of the Tailhousing.  The Bearing & Seal will need to be replaced after a good cleaning.

Tail Housing (before)

First I knocked out the Bearing & Seal using a metal pipe (from the inside out).  When cleared I cleaned the entire unit.

Showing Bearing & Seal removed (pre-cleaning)

Bearing In-Place ( the seal is next)

The bearing came with a retaining snap ring installed (I removed it and discarded).  It is not needed for this application.

Once the bearing & seal were installed I replaced the large cup washer back over the out-put spline (It holds the shaft in-place) and reinstalled the tail housing.  Then I reinstalled the shifter assembly.

All back together

Next (lastly) the Clutch fork & Throwout bearing were installed.

In true TR6 fashion the cross pin that retains the clutch fork onto the clutch shaft was sheared off.  When it was replaced (New shaft & cross pin) I performed an additional upgrade as described by Roger Williams’s “How to restore Triumph TR5/250 & TR6”.  A 1/4″ holl was drilled thru the clutch fork & shaft and an additional 1/4-24 bolt was added.  You can see this in the picture.

Also the Cluch shaft beadings were replaces as well as a new throw-out bearing (high performance).

New Clutch Shaft Bearings

I used a 16mm socket to remove / install the bearings.

Clutch Forf & Shaft Installed

You can see the additional cross bolt and the replacement pin is wired.  The cross bolt is secured with a nylock.

High Performance Throwout bearing installed

The Transmission is now complete and ready for a fresh coat of paint.

Painted and ready for re-assembly

This section is complete:  I will move onto completing the Chassy next.

Published on April 25, 2010 at 7:41 pm  Comments (4)  

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4 CommentsLeave a comment

  1. This is a GREAT web site!
    I just purchased a ’76 TR6 that I plan to do a body-on….or body-off (I haven’t decieded which)… restoration. Your example should inspire me to try to do as well. I may be asking for guidence, now & then.
    i would like to ask you for details of your wood structure to hold the body above the frame. My e-mail is sl00000p@yahoo.com, and I live in the Dallas, Tx area.

  2. Fantastic web site !
    Hope to do a rebuild on my 76 TR tranny this winter. Was wondering where you purchased the rebuild kit ? TRF has a kit also found one at Quantumechanics but very different pricing between the two.
    TR6jw1@ gmail.com

    • Jim:
      I purchased most of the Transmission components (including the rebuild kit) from Victoria British.

      Transmission Overhaul Kit 2 2656 Victoria British $249.95 11-Jan-10


  3. Greetings from California! I’m bored to death at work so I decided to browse your website on my iphone during lunch break. I really like the knowledge you present here and can’t wait to take a look when I get home.

    I’m amazed at how quick your blog loaded on my phone .. I’m not even using WIFI, just 3G .
    . Anyways, very good site!

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