Thread: M6 to A4 conversion guide for 98-02 F-body

Stealing this back from LS1 tech since I did all the work for it, hopefully it can help you guys out! Feel free to make it a sticky if you wish!

T-56 to 4l60E swap in an 02 F-body

What you will need:
4l60E Automatic transmission
Torque converter w/bolts
Flexplate w/ bolts
Transmission cooler
4L60E shifter with cables, Park Neutral switch and shiftlock controls
4l60E shift handle
Automatic pedal set
Auto transmission dipstick
Transmission shift lever
Shifter cable bracket (mounts on transmission pan)
Automatic console top
4l60E transmission crossmember
4l60E Torque arm mount
PNP switch wiring pigtail
Shiftlock control wiring pigtail
Automatic trans wiring harness
Automatic PCM or have yours re-flashed
Trans temp gauge (optional)
Trane temp manifold ( optional)
9X9 piece of sheetmetal
4X4 piece of sheetmetal

Stage 1: prepping the car
Disconnect the negative battery cable
INTERIOR: Part 1
1. Remove the Shifter handle
2. Remove the upper console, disconnect the TCS switch (if present), ashtray light and cigarette lighter
3. Remove the lower console, disconnect the auxiliary outlet connector
4. remove the rubber shiftboot
5. Remove the front driver seat and rear driver seat
6. Remove the underdash panels on the driver and passenger side of the car
7. Remove steering column (Not required but it makes the pedals easier to get out, I just worked around it)
8. Disconnect the clutch master cylinder, the throttle cable and brake control lever from the pedals
9. remove the clutch master cylinder from the firewall, ijust left it in the engine bay for now
10. Disconnect the connectors for the brake lights, clutch override and cruise control (cruise is on BOTH the brake pedal and the clutch)
11. Once disconnected you can unscrew the switches for the brake lights and cruise control from their respective pedals
12. Remove the throttle pedal, it is held on by 1 clip
13. Remove the 2 13 MM bolts (one is way up above the pedals) and the 6 13MM Nuts that hold the pedals in place
14. Next rotate the pedals CAREFULLY over the steering column (if installed) or pull them out if you took the column out.
15. Put the brake light and cruise switches onto your A4 pedals and install the pedals in the reverse you took the M6 pedals out, it is a bit easier
16. Hook up the wires to the switches that are present. Leave the clutch override disconnected for now and the way I dealt with the cruise control switch was to press the button in and tie it tightly with electrical tape and a zip tie. Another way to do it is to find an automatic car and get the electrical pigtail off of the pedals that doesn’t have the extra connectors for the clutch pedal, I couldn’t find one and it is no longer available from GM.

Underneath/engine bay: Part 1
1. Disconnect the 4 Oxygen sensor connectors
2. remove the exhaust from the headers back
3. Remove the driveshaft
4. Remove the driveshaft loop (if installed)
5. disconnect the VSS, skipshift, reverse lockout and pull the harness ont top of the transmission as far as possible
6. Remove the starter motor and inspection cover, disconnect the wiring harness ground next to it
7. Disconnect the low oil sensor and crank position sensor and remove the connector from the AC compressor
8. Loosen or remove the fan belt
9. Remove the alternator, or at least loosen it enough to get the connector off the alternator, there is also a ground on this side up on the fender
10. Remove the ground wire on the driver side of the block
11. Now you should be able to pull the wiring harness up to the top of the engine CAREFULLY, I think I covered all the connectors but check if the harness gets stuck
12. Now remove the following connectors on the top of the engine (There may be a few I can’t remember off the top of my head so make sure you get them all)
a. Intake air temperature
b. Mass air flow
c. Throttle position sensor
d. Idle air control valve
e. Coolant temp sensor
f. All 8 fuel injectors
g. Fuel pressure sensor
h. Canister purge valve
i. MAP sensor
j. Cam sensor
k. Low oil pressure sensor
l. Knock sensors
m. Grounds on the back of the driver side head (it is a 15MM bolt)
n. A/C accumulator
o. The 4 connectors on the passenger side fender
p. The 2 vacuum lines that are bundled in the harness
q. Both connectors on the PCM
13. Next climb in the passenger side of the car and go under the dash by the kick panel and disconnect the two connectors that run through the firewall.
14. remove the PCM
15. Remove the firewall grommet and pull the connectors that run into the car out into the engine bay
16. If you didn’t miss any grounds or connectors you should be able to get the harness out now.

Transmission Removal:
1. Remove the shifter handle from the transmission
2. Raise and support the car, then support the rear axle separately
3. Remove the torque arm and transmission mount
4. Put the transmission on a transmission jack and remove the crossmember
5. Support the engine with a block of wood and stand under the oil pan
6. Remove the hydraulic clutch line from the master cylinder (if still hooked up)
7. Remove the 8 15MM bolts that hold the transmission to the bellhousing (don’t miss the one by the vent tube!)
8. Slide the jack backward from the bellhousing (you may need a pry bar) until the input shaft is clear of the bellhousing, then drop the jack down and put the old transmission in a safe place
9. Now remove the 13MM Bolts that hold the bellhousing to the engine, then remove the bellhousing
10. Remove the pressure plate, clutch disc and flywheel
Part 2:
Installing the new transmission
1. Put the new wiring harness on top of the engine and get the transmission and O2 sensor harness down the back of the engine. Now may be a good time to get the grounds on the back of the head and the cam, oil pressure, knock and MAP sensors plugged in
2. Install your dipstick tube
3. Install the flexplate
4. Put the automatic transmission up on the jack and install the torque converter, make sure it goes in all the way, there should be roughly 1 ? inches between the front of the bellhousing and the converter body, if there isn’t it isn’t all the way in.
5. Put on the torque arm mount, shift control lever and shift cable bracket
6. Try to get the torque converter and flexplate holes closed to lined up
7. Slide the transmission up into place making sure to line up the dipstick tube on the way up.
8. Once it is in place go ahead and put in the 13MM Bellhousing bolts and torque them down
9. Now line up the torque converter and flexplate and get the bolts in there and torque them down
10. Install the new transmission crossbrace and transmission mount
11. Plug in the 20 way connector and VSS and the transmission is in place
12. Reinstall the torque arm and the car can go back on the ground

Underneath and Engine bay, Part 2:
1. Reinstall the driveshaft and driveshaft loop (if installed)
2. Plug in the alternator and re install it
3. Install and hook up your front O2 sensors if possible
4. Connect the crank position and low oil sensors and hook up the ground on the passenger side of the block
5. reinstall the inspection cover and starter motor
6. Install the transmission ground somewhere to the body
7. Hook up the driver side engine block ground and the ground up on the driver side fender area
8. Lower the car back down to the ground
9. Position the wiring harness so it lays properly on the engine then connect all of the connectors, I started on the passenger side and went around the engine then up to the front
10. Once you have them all hooked up run the wires through the firewall under the PCM and hook up all the looms and the harness is in place
11. Install the PCM and hook the main connectors up to it. And that should be it for the harness

The floorpatch and shifter installation
-This was the biggest pain of the install for me, so be patient!
1. Get yourself a 9"X9" piece of sheetmetal to start with
2. Trace the basic outline of the hole in the floor FROM THE TOP onto a piece of paper
3. cut the paper to the outline you traced and put it on your 9X9 piece of metal
4. Take a marker and trace the outline onto your sheetmetal and cut it with tin snips
5. Take the marker and the metal to the car. Put the piece of sheetmetal in place, odds are you are going to have to tweek it. Worry about the front and back first and get them how you want them. Cut it accordingly and hit with a sheetmetal hammer until the front and back fit nicely on the floor.
6. Once you get the front and back the right size take your marker and draw a line on each side of the metal patch where you estimate the car starts to curve
7. Now I don't have any metal benders but it did find out a 3 inch piece of PVC in a vise gives you a real good curve. We put a decent curve in it on each side then went back to the car and hammered it down (gently) to the right shape. At this point it required some more trimming so we got that done and it fit almost perfectly.
8. Take the sheetmetal back out again and file down all the sharp edges you made before you put your eye out!
9. Now with that done get back in the car and bring your old underconsole shift boot with you. Lay the patch down and put the boot over it exactly as it would be if you were putting it back in the car. Take the marker and mark the top 2 holes and bottom 1 hole on the boot onto your patch. Take it all out AGAIN and head to your drill or drill press (highly recommend a press for this)
10. Drill the 3 holes out, I think we used a 3/8 bit, You want the holes to be BIGGER then the screws, trust me you won't get it dead on unless you spend hours doing this. Once the 3 holes are drilled it's back down to the car.
11. Check the alignment of the holes and file them out as necessary to get the screws in. FYI: the patch stripped 2 of my screw holes in the car, I fixed this by using a larger screw so be warned. Now reinstall the patch and the boot and screw them down. Mark the rest of the holes and repeat step #10.
12. Now with that done it is time to drill the holes for the shifter. Before you do this you MUST get the old bracket off the Airbag module. It is tack-welded on so tap it off with a hammer and chisel. Remove the shift boot and re-install just the plate. Then take your shifter, put the 2 back bolts in and find out you have a 1 inch gap between the floor and the shifter. Not a big deal, time to get creative. Mark where the holes need to go on the floor for the shifter with an awl (can't get a marker through the holes), take it all out and head back to the drill
13. Drill out the 2 holes then take the shifter and elongate the 2 mounting holes LENGTHWISE only, again you won't get it perfect, at lease we didn't, so this will give you some slop to work with.
-----From here on this is what "We Did" it may or may not be what you want but it works----
14. Grab 2 1/4 bolts, about 2.5 inches long. Grab 2 flat washers, the wider the washer the better as long as it is 1/4 inch. Take the patch, 2 bolts and 2 washers over to your welder (hope you have one). We welded the bolts through the bottom of the patch to make studs out of them. (I will post up pics eventually so be patient).
15. While it cools go ahead and get 4 3/8 inch nuts (about a 1/2 thick each).
16. Now that it is cool grab the patch and the 4 nuts and get back inthe car again. Re-mount the patch, put the nuts onto the studs and then put the shifter in place, hopefully it fits as well as ours did, it was off by a little bit (thus the elongation of the holes) but it will work.
17. Pull the shifter back out, get the drill with a 2 inch holesaw and drill out a hole as close to the top left corner of the patch as you can get WITHOUT cutting the edges or taking out a screw. This will be for your shifter cable/boot.
18. Now to brace the patch so it won't expand and contract while you are driving look around for an old piece of metal. We found one with holes in it that just happened to coincide with the studs we made so we cut it to length. It will go over the studs and then the 4 nuts will be on top of it. It should add some rigidity to it.
19. Clean it with lacquer thinner, scuff it with 100 grit sand paper, Prime, paint and let it dry, I used Rustoleum on it but it takes a few days for it to get good and hard, so if you are in a hurry use a different paint.

Installing the transmission cooler and temp gauge
This is a play it by ear part, I can’t give you guidance on this because it depends entirely on what kind of cooler you get, I suggest just following the manufacturers instructions on this one, it is not hard to do. Also I made a bracket for the tarns temp manifold, but install it wherever you can if you bought a temp gauge
Wiring the shiftlock control and PNP switch
You are going to need to run a total of 8 wires for the 2 switches, 6 for the PNP and 2 for the shiftlock. The connector pigtails you bought from the dealer for an exceptionally high price should be labeled A-F on the PNP and A-B on the shiftlock the wires go to the following places
PNP switch:
A. Shift Lock control circuit - Black/white wire from shiftlock control solenoid (Connector C200, Pin E)
B. PCM - Orange/Black wire from the white connector (Connector C220, pin H)on the end of the engine harness (the one that is inside the car on the passenger side under the kick panel)
C. Back up Lights - Brown wire, Same connector as above (Connector C220, Pin G)
D. Ground - Light green wire in Connector C400, Pin F (not sure where this one is but I can look it up) or to a chassis ground.
E. Start circuit - Clutch override switch (on the pedal), Purple/white wire
F. Start Circuit - Clutch Override switch (on the pedal), Dark green wire

Shiftlock Control:
A. PNP switch, Pin A
B. Brake light switch

Once that is all done bundle up the wires and tuck them up under the dash and do the following:
1. Permanently mount the floorpatch with some kind of body sealer to keep water out
2. Install the shifter and run the cable through the floor, installing the grommet
3. Put the lower console in ( use your old ashtray light for the light in your shift indicator) and hook up the accessory outlet
4. Install the upper console and shift handle
5. Re-install the seats and under dash panels
6. Raise the car again and run the shift cable through the bracket, lock it in place and put the clip on it, then hook the cable up to the shift control lever on the transmission
7. put fluid in the transmission
8. Re-install your exhaust and hook up the negative battery cable and you are all set to try it out

Testing your new transmission

Testing the Brake lights: Step on the brake, they should illuminate, if they don’t the switch may be unplugged or out of adjustment. To adjust it just turn it in it’s threads until it works

Testing the PNP Switch and shiftlock control: With the car SHUT OFF Put the car in reverse and you should get your reverse lights. Next put it back in park, put on the E-brake and block the drive wheels, just in case. Then start the car (if you haven’t added fluid to the transmission yet now is the time). It should start up and not try to move. Now with the brakes off try and move the shifter (be careful because if the shiftlock doesn’t engage you are going to end up in reverse) if it doesn’t move then the shiftlock is working. Now step on the brake and the shiftlock should disengage allowing you to put it in gear. If it works put the car in park and shut it off. If it didn’t work check the 2 wires and repair accordingly. If it did work, with the car off put it in any gear and bump the ignition. The car SHOULD NOT START, if it tries to start troubleshoot the appropriate wires until it works right.

Now warm the car up to operating temp (hopefully you decided to put in a trans temp gauge to keep an eye on it), run it through the gears and top off the fluid, check for leaks and then go for a ride.

Thank you for the great write up. I am sure this will be of great use!

Indeed, thank you

Is there a lot of people that want an A4 over an M6 even to the point of swapping the tranny? If so that could really help in me buying a car because that way I could swap the A4 out.

Well if you wanted the fastest time possible. Don't waste your time with an M6. The A4s have the real potential the faster you go. And it is less things you have to do when the light turns green.

i agree that an Auto is a better 1/4 mile selection but i'd much rather have a M6 for toolin' around or the road course. Great writeup man. We need these~Cole~

This is my last clutch. After this one I am going A4.

It is a great write up, I have a hard time driving auto's I like the manual because it gives me somthing else to do. I wish we had had an auto the 98 GTR Skyline I co owned in Japan, I couldn't shift left handed that well lol!

Ya I was fucking up bad. I drove a right hand drive toyota truck in Iraq one day. Damn man that was hard.

Yeah my friend freaked out most of the tracks in the original grand turismo game were in Japan. I could drive the car on the open roads more speedway type tracks was banned from the road course/drift course. My reflexes are retarded right hand driving

Originally Posted by dixonk

This is my last clutch. After this one I am going A4.

That's what happened to me, 3 $3000.00 transmissions and 4 $1000.00 clutches in 3 years, I just got tired of breaking it all the time. In went the auto and nt a single problem since. I do miss the M6 on the regular road though