Upgrading The Manual Drivetrain
This page describes the options available for upgrading the manual drivetrain.
This includes the transaxle, clutch, axles, and brakes.
Technical details on these transmission are available on the Manual
Transaxle Specifications page. You can click on each section
title below for details on that transaxle. Throughout the history
of these cars, there have been several transaxles used on them. The
first 5-speed transaxle was the A465, which was the same as the A460 except
it had a fifth gear bolted on the end of it. The description below
will start with the first transmission that is expectable for performance:
The A525 Manual Transaxle
This transaxle was used on most vehicles until 1986, except for the L-body
where it was used until the L-body's demise in 1988. It's main drawback
is a lack of strength in the casing near the differential due to the steel
plate that is used for the differential cover, and the poorly located left-side
differential bearing. High output engines will actually cause the
transaxle's case to flex due to the deflection of the poorly supported
differential. This flexing causes the gears to mesh improperly, which
eventually tears up the gears and bearings.
This problem can be aided with the installation of a Transmission Girdle
(P4349444) by Mopar Performance, which adds the required strength to the
also makes available an A525 upgrade kit which gives the A525 the Getrag
gearset of the A555. When installing the girdle, be sure to round-off
the left-side differential bearing retainer so that the bolts holes on
the girdle line up with the holes on the retainer. Also, the flange
on the differential cover has to be ground off in the areas where the girdle
contacts it, so that the girdle sits properly. Lastly, try to find
some longer bolts than the ones supplied with the girdle, so that they
take up as many threads as the stock bolts without the girdle.
The other big issue with this transaxle is that it had three different
versions of internal parts. Carbureted engines received much weaker
internal transaxle parts than turbocharged engines did. Be sure to
get an A525 from a turbocharged engine! Look at the assembly number
of the transmission on the tag that is attached to the differential case.
The best A525 transmission you can get is from a mid-1987 or later L-body.
These came with the high-strength, precision-shifting, well-sealing internal
components of the A520 transmissions and were filled with SAE 5W-30 engine
oil like the A520. One of these transmissions can be strengthened
further by installing the A555 internals. Some fabrication may be
required to do this modification.
The A520 Manual Transaxle
This transmission was introduced in 1987 (though a few 1987 vehicles got
the A525). It featured the same gear ratios of the A525, but had
a cast piece for the differential cover and a relocated differential bearing,
which solved the flexing problem of the A525. The positions of the
left-side axle output and the torque strut are slightly different for the
A520, so some fabrication is necessary if it is to be swapped with an A525.
This is probably the most popular transmission for street performance because
it has taller gear ratios than the A555 and a final drive ratio of 3.50:1
for better mileage.
These transmissions should be the same for all engines.
The A555 Manual Transaxle
This transmission was basically a heavy duty version of the A520.
It used high strength version of the A520 case, and had tighter gear ratios
which gave it a final drive ratio of 3.85:1. It featured the Getrag
high-strength gearset, a stronger intermediate shaft, and a stronger differential
with four pinion gears and larger output shafts. This is probably
the most popular racing transmission because of its high durability, but
the shorter gear ratios result in higher engine speeds. Which is
better depends on the application and the personal preference of the driver.
There are a few different clutches available. If you mild-performance
engine, your stock clutch should hold up. If you have problems with
your Turbo I clutch slipping, you can try the Turbo II clutch, which has
more clamping force.
RPS Performance Products
A manufacturer of high performance clutches for turbocharged engines, which
seem to work very well in 2.2L and 2.5L engines. They use a very
strong pressure plate diaphragm, instead of weights, to increase the clamping
force of the pressure plate by 45% to 50%. This coupled with a special
full-contact clutch disc lining that is bonded to the disc makes for a
very strong clutch. They now have three product stages available
for their clutch disc designs.
Their original "Turbo Clutch" uses a brass-impregnated organic clutch
lining to increase the frictional force of the clutch. This, coupled
with their stronger pressure plate, makes for a clutch with over 50% more
holding capability. Their "Carbon Claw" clutch is a new clutch design
that uses a light weight carbon metallic lining that can tolerate much
more heat than an organic lining (stock lining is organic). It is
also up to 30% lighter than a stock clutch disc, which makes for faster
shifting (the syncros have to do less work). The latest RPS design
is their "Turbo Clutch Carbon", which uses the carbon metallic from the
"Carbon Claw" with their strong pressure plate.
Probably one of the most popular alternative to the OEM clutches are Centerforce's
Clutches. They use centrifugal weights to increase the clamping force
of the pressure plate as the engine speed increases. Unfortunately,
there have been known problems with these clutches for our vehicles, particularly
the Centerforce Dual Friction clutch. The other versions appear to
be OK. I recommend RPS clutches over Centerforce.
The Original Centerforce (now called the Centerforce Gold) claims to
have 30% more holding force than the stock OEM clutch, while maintain a
stock pedal feel. Forward Motion
sells the CenterForce II, which provides 60% more holding capacity than
the stock clutch and is recommended for "mildly modified" vehicles.
The CenterForce Dual Friction clutch offers up to 90% more clamping force
than the stock clutch and is designed for "radically altered high performance
vehicles", but is of poor quality of 2.2L and 2.5L engines. Please
do not use this clutch. You can purchase Centerforce clutches through
companies such as
When replacing the clutch, always replace the throw-out bearing.
The throwout bearing for the A568 transaxle is designed better than the
earlier bearings. Be sure to clean and grease the input shaft yoke
so that the bearing slides freely and does not hang up. Use Mobil
1 synthetic chassis grease.
The proper axles for your vehicle depends on the vehicle. Many vehicles
have different wheel bases and therefore require different shafts.
Most manual and automatic axles are interchangeable for any given model
year (except some L-bodies). Vehicles equipped from the factory with
a Turbo II engine usually received heavy-duty axles and CV joints (i.e.
the Daytona Shelby) and these can be interchanged with other axles, as
long as the transmission has the correct output shaft size.
Most stock axles can handle a lot of torque. If you constantly
break axles, you need to make sure that your engine is properly centered.
See the How To Center Your Engine page
for more details.
This page is maintained by Russell W. Knize and was last updated 06/03/99.
Comments? Questions? Email
Copyright © 1996-2003 Russ W. Knize