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Midget 5-speed conversion

To: mgs@Autox.Team.Net
Subject: Midget 5-speed conversion
From: Wayne Kube <wkube@iadfw.net>
Date: Sat, 04 Oct 1997 23:39:34 -0500
For everyone interested in the 5-speed in a Midget project, I scanned
this article from the Texas MG Register newsletter.  The newsletter
itself will be posted at www.tmgr.org in about a week.

Wayne Kube



***********************

Copyright Texas MG Register

from "Texas Chapter News" October, 1997


FIVE SPEEDS AND AWAY

By Stephen Linder


Driving Maryann's MG Midget was no fun at all. The darn old transmission
was so noisy in first gear that it sounded like it was full of broken
glass. Second and third gears weren't too quiet either. On top of that,
the overall final drive gear ratio of the poor little thing was so low
that it was down right poky on the highway. Sixty-three MPH required
4000 RPM from the tiny engine. Four thousand RPM isn't so bad, but
trying to go down a Texas interstate at 63 MPH in a tiny British car can
get you killed. Yes, I could just drive at a higher RPM to get the speed
up, but 75 MPH was pushing 5000 RPM and I'm just not comfortable driving
for prolonged periods that close to the red line and I wanted to be able
to go at least 75 MPH.

So what could I do? I considered a rebuilt transmission which would run
about $900 and I considered buying the parts and doing the rebuilding
myself but that would cost almost as much and I still would have the
low, low gear ratio problem.

While I was pondering the options, a MINI MANIA discount flyer popped up
in my mail box and offered a low price on their 5 speed conversion kit
for the Spridget. The advertisement for the kit said "NO MODIFICATIONS
TO THE CAR ARE REQUIRED." Hot diggity. That's just what I need. A fifth
gear overdrive for lower RPM on the road without sacrificing the
Midget's originality. And a modern 5 speed transmission is bound to be
quieter than a 35-year-old transmission. Right? O.K., a 1980 Datsun 210
5 speed was never offered as original equipment in a Midget, but at
least I wouldn't have to change anything else on the car. Who would know
except me and the people I told?

I ordered the kit from MINI MANIA and it arrived about a month later. In
the mean time I picked up a Datsun 5 speed transmission at a local auto
salvage yard for $100. Pretty cheap! I bought the other parts specified
in the kit instructions from my local NAPA parts dealer.

The conversion kit included a beautifully machined, 5/8 inch thick,
aluminum adapter plate to match the Datsun transmission to the Midget
engine and a custom-made clutch disk to match the splines on the Datsun
transmission (If this clutch disk needs to be replaced someday, where
will I get another one?) as well as a few other special parts.

Carefully following the kit's instructions, I modified the Datsun
transmission and installed it and the beautifully machined adapter plate
and the custom-made clutch disk on the Midget engine. The only
modification to the Midget engine was to replace the pilot bushing in
the crankshaft with a specially made one supplied in the kit. That was
O.K., the old one was worn out anyway. Besides, no one can see the
bushing when it is installed so it doesn't count as a modification.  The
foregoing didn't take long and then it was time to slide that old engine
with its shiney 5 speed, fully synchromesh transmission back into the
car. Up it goes, in it went. Sliding, sliding, sliding, CLUNK. Clunk is
not good. The engine was firmly wedged between the its two ends and at a
point on the bell housing up against the cross member under the heater
box. No way was that engine and transmission going to budge another inch
into the car.  While musing this dilemma, I remembered a note in the kit
instructions. "You may have to 'dent-in' the cross member just under the
heater box to facilitate the installation of the engine and
transmission." But the ad said "NO MODIFICATIONS TO THE CAR ARE
REQUIRED." Well, no way was I going to dent-in" any cross members on
this precious little car! Then I saw the problem. There was a
protuberance on the top of the transmission that was hanging up on said
cross member. Saw, saw, saw, file, file, file. Off came the lump. I put
the engine back in. Slide, slide, slide, CLUNK. This time the engine was
wedged by the tail shaft, the transmission bell housing against that
cross member and the engine front pulley. At least the engine went in a
few more inches. Out came the engine. File, file, file a little more on
the bell housing. Back goes the engine. CLUNK. Out came the engine.
Wham, wham, wham, wham. It's just a little dent under the cross member.
No one will notice. Back goes the engine. Slide, slide, slide. Eureka!
It is in. Well, almost in. The engine was now sitting about one inch off
the passenger side motor mount. It seems that the beautifully machined
adapter plate was about 1-1/4 inches wider than the space afforded it.
Out came the engine. Saw, saw, saw, file, file, file. About 2 hours
later the offending portion of the mounting plate was history. Back went
the engine. At last! The engine and transmission were resting
comfortably on their soft rubber mounts.  The remainder of the
installation went quite well.  Just a little hydraulic plumbing was
required to relocate the clutch slave cylinder to the driver's side of
the transmission. After that all I needed to do then was to bleed the
clutch and go for a little test drive.

Before I could do a test drive, I noticed a couple of little problems
with the clutch. The Toyota clutch slave cylinder specified in the kit
is not a good choice for this application. The foot force required to
depress the clutch pedal was enormous. The other problem was that the
clutch was fully released after only about one half  inch of pedal
travel, and if you pushed a little more, the clutch started to reengage.
This is called "over releasing," I found out later. I tried the test
drive anyway. I found that I could over come the excessive clutch pedal
force by using both feet on the pedal.  Ever try to get two feet on a 2
square inch pedal? Even at that, the reaction to the force of depressing
the clutch would cause me to slide up the back of the driver's seat. So
I held onto the steering wheel with both hands to keep myself on the
seat. But with both hands on the wheel, how am I supposed to shift
gears?  With a little practice, I developed a technique. I used the "two
feet, two hands" method to depress the clutch and then I would let go of
the wheel with my right hand and bat the gear shift lever into the next
gear before the returning clutch force succeeded in shooting me out
through the top of the car and onto the street behind.

The "two feet, two hands" method fell short, however when it came to
executing coordinated gear changes because with both feet on the clutch
pedal there was no foot left for the gas pedal. The little Midget would
lurch into motion, smoothly accelerate to 5000 RPM in first gear, but by
the time a shift to second gear was completed, the Midget had slowed to
a crawl. Other drivers gave me a wide berth and many curious looks.

Feeling that Maryann might not like the way that the clutch worked, I
decided to do something about it. Luckily, the clutch slave cylinder
from a 1972 MG Midget has a more favorable geometry, even if it didn't
fit on the bell housing very well. After some additional modifications,
the 72 Midget slave cylinder solved the excessive force and insufficient
travel clutch problems and replacing the Toyota part with an MG part
made the Midget even more original.

Well, was it worth all the trouble? A big YES! The Datsun 5 speed
trans-mission is a perfect match, gear ratio wise, to the little 1275 cc
Midget engine. The transmission is relatively quiet, it has a
synchromesh in first gear, and the fifth gear overdrive allows the car
to easily hum down the highway at 75 MPH, while the engine turns a safe
4000 RPM, and to go faster than it has ever gone before in it's 35 years
on this earth. Driving Maryann's MG Midget is now a lot of fun.

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