Installation Overview
(reprinted from Car Craft Jan 1994)
Tremec's GM aftermarket replacement T56 assembly uses a
26 spline input shaft that mates with the existing GM clutch assembly. Also included
is a special adapter plate that bolts the transmission to the stock T5 bellhousing.
Borg Warner developed the kit using a ' 92 Camaro equipped with the optional '89-92
dual-catalyst exhaust system. Although the exhaust pipes remain unmodified, the hanger
that previously attached the pipes to the transmission mount is discarded. Most GM
F-cars (Camaros, Firebirds, and Trans Ams) use only a single catalyst, which, if
anything, should provide even more clearance for the transmission. The kit moves
the '90-92' T5 mount 1.9 inches rearward to mate with a sectioned and rewelded '93'
GM F-car transmission crossmember. This in turn requires correspondingly shortening
the rear differential torque arm by 1.9 inches. Retain the stock 27-spline skip-yoke,
but shorten the driveshaft by 2 inches.
Bellhousing and Clutch Linkage
| The '93 F car uses a "pull-type" clutch
assembly, and the T56's front face is different from traditional GM manual
transmissions. Tremecs's adapter plate provides the solution -- it bolts
the new trans to the earlier T5 bellhousing and permits retention of the
existing T5 V8 clutch system without alteration. |
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| Stock T5 V8 bellhousings rotate the T5 trans 18
degrees counterclockwise from "straight up." Borg-Warner's adapter
plate returns the T56's orientation to "straight up". Old Muncie/T10/Saginaw
transmission also mount "straight up." Use of the old four-speed
bellhousing with the T56 adapter would thus rotate the new trans clockwise
from the vertical (leaving the mounting pad nonparallel to the crossmember).
Instead, use a T5 bellhousing when replacing an old four-speed with a T56.
The '83 F-car T5 V8 bellhousing is the best choice for old musclecar retrofit
application, as it still uses mechanical clutch linkage. This unit is no
longer available from GM, so ask the salvage yards. Lakewood offers an equivalent
scattershield. The '84 - '92 Camaros use a bellhousing set up for hydraulic
linkage. |
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Cross members Modification
No detailed drawings of the modification required to mate
a '93 F-car T56 crossmember to the earlier F-car T56 crossmember exist, so it's a
cut and try proposition. The '83 and later F-car installation uses the original T5
mount. For earlier conversions, use the stock 3.75 inch bolt spacing (non-Turbo 400)
mount for the chassis in question, but attach it to the trans using metric M10x1.5x30
mounting bolts.
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| Use four countersunk sockethead capscrews (arrows) to attach
the adapter plate to the bellhousing. Note that the palate corrects the trans orientation
to "straight up." Carefully align the clutch disc splines with the input
shaft splines, then bolt the trans to the adapter plate. |
The orginal flat T5 crossmember (left) won't fit the T56. Instead,
get a '93 T56 crossmember (center). Modify it so it looks lite the one on the right.
This involves drilling a new hole (A), cutting the right side off to chane its angle
(B), and adding new material (C). Details follow: |
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Start with the left-hand side. The new crossmember attaches to
the rearmost two threaded factory mounting holes. This requires drilling
one new hole in the crssmember that corresponds to the location of the rear
most subframe hole. To find the proper hole location, scribe an easily visible
line on the subframe through the rear bolt hole that is parallel to the
vehicle's longitudinal axis. Scribe a second line at a right angle to the
first line through the rear bolt hole. Make the lines long enough so they
extend beyond the cross member when it is in position. Bolt the crossmember
and mount to the T56 trans. Install the forward left-hand cross member to
subframe bolt (A). Using the ends of the previously scribed lines as a baseline,
extend them across the crossmember. Remove the crossmember and drill a 10mm
hole at their intersection point (B). |
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Remount the crossmember to the
trans and left-hand subframe. Cut off the crossmember to the right of
the mounting pad (A). Bolt the cut-off section's front hole to the rearmost
existing tapped hole in the frame channel (B). Section and add new pieces
of material (C) to make the crossmember's existing rear hole flush with
the frame rail kick-up. Drill a new hole into the frame rail that corresponds
to the rear hole in the crossmember (D).
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A blind Rivnut or Nutsert is the "elegant" solution
for suppling the female threads required by the newly drilled bolt lole. The low-buck
solution is a 2x3x1/2 inch-thick stel or aluminum block. Shove it into position through
the large existing hole in the frame as shown so it lines up with the newly drilled
crossmember mounting hole (see arrow above), then drill and tap it for metric M10x1.5
threads. Adding a second (but countersunk) bolt hole to the frame and block will
keep the block from twisting out of position. Finally, bolt the crossmember solidly
into position using all four bolts, and final-weld all joints. |
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T56 Electric Reverse Lockout
Unlike the T5 or traditional four-speed transmissions,
the T56 uses an electrically actuated reverse-lockout solenoid system
to prevent inadvertent shifts into Reverse gear. In production applications,
the vehicle's computer will power up the solenoid only if vehicle speed
is less than 5 mph. For retrofit use, use a monetary switch to operate
the lockout solenoid. B&M, Hurst, and even nitrous oxide companies
offer shifter handles with these switches built in (normally, they're
used for controlling nitrous or the Roll Control). Connection with the
lockout solenoid at the trans requires a GM Metipack connector assembly.
If it is not desired to enable the solenoid, the Neutral to Reverse shift
can still be completed at the vehicle speeds less than 5 mph by overriding
the lockout assembly with the emergency "crash-through" feature.
The lockout assembly plunger is spring-loaded and a high side effort on
the shift lever compress the spring, overcoming the lockout.
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| Shorten the rear differential torque arm 1.9 inches by sectioning
and rewelding in the area shown. |
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| Production GM T56s accept only a fully electronic speedometer
connector (A) In both above photos, (B) indicates the location of the electric reverse-lockout
connector receptacle, a common feature on all current T56 transmissions. |
Tremec machines the aftermarket version's extension housing
for the traditional GM speedo cable connections (A), which accepts both full-machinical
cables and the hybrid '90-'92 magnetic pickup. Use GM T5 drive and driven gears for
speedo calibration. Although the speedo hookup is 2.6 inches farther rearward, the
existing cable should still hook up. Shifter location is also revised to conform
to the T5 location, eliminating the need for any floorpan modifications. |
The completed T56 transmission shows the new adapter plate,
relocated and modified cross member, and shortened torque arm.
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Critical Dimensions
Listed below are the critical dimensions of the T56 in comparison to T5 and traditional
four-speeds. Metric dimensions are converted to inches and rounded off to the nearest
0.1 inch.
| Trans Model |
A
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B
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C
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D
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E
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F
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| GM Super T10 Muncie |
6.3
|
14.2
|
23
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n/a
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n/a
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3.75
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| GM T5 V8 |
6.3
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16
|
25
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19
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21.2
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3.75
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| GM T56 F-car Prod |
4.9
|
21
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26.4
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21.1
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23.9
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3.75
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| GM T56 F-car After- market |
6.3
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21.5
|
27
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21.6
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21.6
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3.75
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Manual Transmission Parts 
