Please study all photos carefully- and read text file at link button
Unused Celica transmission:
I first started off with a aluminum body Celica gearbox (they are also made with
cast iron)- and ran across a Corolla T-50 box at a friend's house while
measuring/fitting this one. I think it would work too, but be a much
tighter/heavier fit. After seeing a T-50 box, I immediately bought one (whole
parts car)
T-50 gearbox dissasembled to make adapter plates and to remove
input shaft for mating:
Please read the text files as to details on the plates and shaft, it's all
needed to understand.
The first (of 2) adapter plates is actually just the rear part of the T-50 bell housing cut off and milled flat.
The sawing does not have to be perfect- the mill will clean it
up easily and get it true. Just clamp it down thru the shaft hole as you see
here.
This plate will also become the template/pattern for the 2nd "main" adapter
plate, made in the next step.
Both adapter plates finished, inbetween the Triumph bell housing- you can see
how they fit together here. The material on the 1st plate is milled to 1/16"
lower than the center bearing flange. There is also a support below this for the
lower transmission shaft support that needs to be left unchanged. You can see
the hole center of the 2nd plate will clear this area. The 1st cutoff/milled
plate is used as a template-pattern to lay out the 2nd adapter plate.
The main plate adapts the Triumph to the different Toyota bolt patterns- see
text files for layout details. After the main plate is made, the assembly is
test fit- and input shaft length cutoff mark made on T-50 shaft. Note Triumph
shaft already cut-bored in photo.
Cutting the Triumph shaft to length:
This needs to be done in a lathe while turning (to keep it square). Mounting the
grinder in the tool holder may help. Again- see the text for details.
Drilling pilot hole for socket:
Easier than you might think, as the material is not case hardened in the center.
Only the surface is hard- to about 1/8" deep. Do use a pilot bit to start hole
center.
After drilling 1/8" pilot hole 1 1/4" deep, enlarge to 5/8" ID x 1 1/4" deep.
Use a boring bar to true hole in shaft: This step is critial-
the hole must be perfectly true and proper size for the .002" interference fit
with T-50 shaft "pin", made in the next step.
You must use a boring bit for this- here shown out of the lathe for clarity.
(harder to see clamped in toolpost) This hole will be the "socket" for the "pin"
made in the next step.
The T-50 shaft being turned for the "pin" just mentioned.
A ball bearing grinder mounted in the toolpost is needed for this step- grinder
wheel turning while shaft is turning in lathe will turn it down nice and smooth.
This also is the only way to get thru the case hardened metal. The pin section
is carefully turned/ground down to size- for the .002" interference fit. Then
cut to length with grinder
Shafts ready to assemble- again read the text files as you will
only get one try at this!
Triumph shaft goes into oven to heat/expand- T-50 shaft goes into a freezer to
contract in size. Your machining size accurracy is very important to this
interference fit.
Shafts assembled together with interference fit- but not yet
welded.
Before welding rechuck in lathe and check runout (deviation) with a runout
gauge- mark high side if not true.
Shafts after welding: Don't overweld it- and weld opposite the high side if
there is one (this will help retrue it)
I used my mig welder for this, with about a 1/8" to 3/16" bead all around (
about one-quarter at a time, on opposite sides each pass )
New conversion assembly alongside a spare stock GT-6 :
This is the point where the driveshaft is measured for cutting and mating to
T-50 end...also gearshift lever cutoff, shortened, and mated to Triumph threaded
cutoff end.
Side view- stock GT-6 top...T-50 conversion bottom.
Closeup right side view.
Front left view. Note recessed bolt heads in 2nd adapter plate.
Front right view.
Fitting assembly into car: This is done with
engine in place.
A few inches of sheet metal from the center tunnel rear will need removal for
the longer transmission/driveshaft.
Left view: This is also when the rear bracket is cut (from the
stock T-50 steel bracket) and fit- welded into place.
The transmission and bell housing will need to be removed again for welding- be
sure to mark and cut the speedo drive cable hole at this time too.
The rear T-50 stock mount/bracket. Ends are cut off to make a perfect fit in the Triumph frame, with 5" or so of the center remaining. The original rubber bushing mount on the T-50 is used in the center hole.
Rear mount welded in place: Also note speedo cable hookup and
gearshift lever welded to length.
The speedo cable core is the stock T-50 core- turning inside a mated outer cable
housing. Again, read the text info for details.
Driveshafts cut and ready to mate:
Quite simple really- wrap two spaced "rings" of masking tape to shim T-50 short
end inside Triumph long end. It should only take one or two layers, as they are
close in size. Then reweld carefully. I did not need to rebalance mine.
Driveshaft ready to weld prep.(grinding). Tack weld all round first, then weld
in small sections, 1/8" bead. (as the originals were)
T-50 conversion installed- fitting my home made fiberglass tunnel cover.
Note- my cover is made to suit my personal tastes- the stock tunnel will work
with minor cutting at the rear. (and addition of a little fiberglass to neaten
things up) The stock dash support will also fit fine- I just don't use it.
After installation left view- updated recent photo.
Note new dashboard, door panels, carpet, etc....new carpet is still wrinkled and
lumpy.
After installation right view. You can see in this view the tunnel is much lower
than stock- also without dash brace and other padding a bit more leg room
is gained.
Center view.
My GT-6 at present moment, in primer finish prepping to repaint black again.
Some of the trim and badges are off to facilitate sanding just now.Also a new wire wheel kit has replaced the old bolt on type wire wheels shown in the other/earlier photos.
Left view at present.
Engine left view. Engine is all stock, but will add a electronic ignition kit to
replace/upgrade points in a few days from now.
Engine right view
My wife's '69 Midget, and my '72 Triumph (5 years ago)
My Triumph again...earlier photo, just after conversion.
Just after installation 5 plus years ago. I've replaced most the interior since.
My wife's '73 GT-6, that we still own. I've been wanting to do another
transmission conversion on it someday, having already gathered the Toyota parts
for the project...just haven't found time as yet. The stock gearbox is ok and
working (although well worn), so no hurry on it.
My wife's Midget (again)
Parts cars I still have, and needing to sell some of them soon.
The Corolla donor-parts car, bought for $100 (had a major engine problem). The T-50 gearbox was in very good condition- no repairs needed.
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Drawing of the T-50 gearbox