4+3 to ZF Conversion
Pro
Joined: Jan 2003
Posts: 664
Likes: 119
From: Albany OR
Here's what I did on my 85 4+3 to ZF swap:
Used ZF from ebay, my is out of a 90, make sure it is from a L98 or LTI/LT4 car not a LT5 car, different input shaft lengths.
New bellhousing, mine was a take off from an LT4 so it is the magnesium version.
I used a Fidanza aluminum flywheel, they make one specifically for this swap.
I bought an OEM clutch assembly (you have to get the one that is for the year that your ZF is, the TO bearing is different for the early ZF’s and the later ZF’s).
I bought new clutch master cylinder and slave cylinder for a ZF equipped car.
I bought a used clutch hydraulic line from ebay.
I bought a used starter from ebay (you have to get the one that matches the bellhousing you will be using, early ZF belhousings use the large nose starters like your car has, later ZF bellhousings use the small nose gear reduction type starters).
I bough a new clutch pilot bearing for ZF car, I think your 4+3 one will work though.
I bought a Hurst short throw shifter from ebay and installed before I put the ZF in the car, much easier than when the tranny is in the car. The extra benefit besides the shorter throw and better feel is that the stock 4+3 interior shifter trim plate will work, I guess with the stock ZF shifter the trim plate opening is to narrow to be able to shift the ZF into reverse.
I bought a new drive line. The ZF and 4+3 are the same length, just a different size yoke for the tranny tail shaft, much larger on the ZF.
I bought new pig tails for the speed sensor and reverse light connection, they are different than the 4+3.
You will need to cut out the old shifter from the tranny tunnel, the hole needs to be a little bigger than the old shifter pocket especially at the front. Then you will need to fabricate a fiberglass or metal patch to cover the hole. I used metal.
I needed some longer bellhousing to engine block bolts for the thicker flrange on teh magnesium bellhousing.
You will need the correct bolts for the tranny to bellhousing.
Flywheel bolts will depend on what flywheel you end up using, my Fidanza came with new flywheel bolts.
I think that is everything, at least what I remember.
Some people have used different clutch and flywheel set ups. What I used has worked well for me so far.
The C beam between the tranny and the diff. are the same.
Anyway, this is what I did and I am happy with the results.
Brian
Used ZF from ebay, my is out of a 90, make sure it is from a L98 or LTI/LT4 car not a LT5 car, different input shaft lengths.
New bellhousing, mine was a take off from an LT4 so it is the magnesium version.
I used a Fidanza aluminum flywheel, they make one specifically for this swap.
I bought an OEM clutch assembly (you have to get the one that is for the year that your ZF is, the TO bearing is different for the early ZF’s and the later ZF’s).
I bought new clutch master cylinder and slave cylinder for a ZF equipped car.
I bought a used clutch hydraulic line from ebay.
I bought a used starter from ebay (you have to get the one that matches the bellhousing you will be using, early ZF belhousings use the large nose starters like your car has, later ZF bellhousings use the small nose gear reduction type starters).
I bough a new clutch pilot bearing for ZF car, I think your 4+3 one will work though.
I bought a Hurst short throw shifter from ebay and installed before I put the ZF in the car, much easier than when the tranny is in the car. The extra benefit besides the shorter throw and better feel is that the stock 4+3 interior shifter trim plate will work, I guess with the stock ZF shifter the trim plate opening is to narrow to be able to shift the ZF into reverse.
I bought a new drive line. The ZF and 4+3 are the same length, just a different size yoke for the tranny tail shaft, much larger on the ZF.
I bought new pig tails for the speed sensor and reverse light connection, they are different than the 4+3.
You will need to cut out the old shifter from the tranny tunnel, the hole needs to be a little bigger than the old shifter pocket especially at the front. Then you will need to fabricate a fiberglass or metal patch to cover the hole. I used metal.
I needed some longer bellhousing to engine block bolts for the thicker flrange on teh magnesium bellhousing.
You will need the correct bolts for the tranny to bellhousing.
Flywheel bolts will depend on what flywheel you end up using, my Fidanza came with new flywheel bolts.
I think that is everything, at least what I remember.
Some people have used different clutch and flywheel set ups. What I used has worked well for me so far.
The C beam between the tranny and the diff. are the same.
Anyway, this is what I did and I am happy with the results.
Brian
Advanced
Joined: Jul 2005
Posts: 86
Likes: 0
85 4+3 ZF swap
Hi im a new member but i am also have the same conversion done, although my corvette is an 85. You see, I have had this mechanic working on my car for three months now and he is just giving me the runaround, at the moment he is telling me that i need a whole new wire harness and that the kit is $900. On your post you said you need new pig tails? Could you please tell me where i can get these.
Pro
Joined: Jan 2003
Posts: 664
Likes: 119
From: Albany OR
KCcorvette,
I sent you a email response. I read your email before I saw your post on this thread. I thought this thread was dead as I had not seen any activity on it in over a week so I no longer was looking for it. Hope the email reply helps.
Brian
I sent you a email response. I read your email before I saw your post on this thread. I thought this thread was dead as I had not seen any activity on it in over a week so I no longer was looking for it. Hope the email reply helps.
Brian
Melting Slicks
Joined: Apr 2000
Posts: 3,490
Likes: 2
From: Oviedo FL
I have posted this on many occasions...
CorvetteZ51Racer did this a couple of years ago and I copied his instructions:
Swapping a ZF 6 speed transmission into a 1984-1988 Corvette involves a lot of work. First and foremost, the shifter accomodations are different between the ZF and 4+3 transmissions. Making the modifications for the shifter linkage is the most daunting part of the swap. Other than the fiberglass fabrication in the transmission tunnel, no fabrication work needs to be done: everything else is merely parts swapping.
Parts list
-----------
1) ZF 6 speed transmission out of an '89-'96 Corvette w/ bellhousing and shifter
2) Driveshaft from the same (actually, all you need is the output shaft yoke from the ZF driveshaft as the shafts themselves are the same, but they are VERY hard to find separately)
3) For the clutch setup, you have a few options:
a) stock ZF hydraulic clutch system, dual mass flywheel, and stock ZF clutch assembly
b) stock ZF hydraulic clutch system, single mass flywheel, stock ZF clutch assembly, and single mass conversion clutch pivot ball** Note: '85-'88 4+3 flywheels will work just fine. The '84 FW is too thin to use with a ZF-style clutch. Despite the fact that 4+3 clutches are listed as 10.75" clutches and the ZF is 11", it will work.
c) stock 4+3 hydraulic clutch system, single mass flywheel, McLeod p/n 1345 push-type throwout bearing conversion, and 4+3 style clutch.
4) IF your bellhousing is from a '92-'96, you will also need a new starter motor (LT1/4's use mini starter). '89-'91 bellhousings retain the 4+3 style starter motor.
5) If using the ministarter, you will need a longer (54" if memory serves...maybe 60") starter cable.
6) If possible, '89 center console plate. If you can't find one, don't stress, the '84-'88s will fit with a minor modification.
7) Fiberglass cloth, resin, and acetone.
Process
-----------
The first thing is to remove all of the 4+3 related parts. Do not forget to remove the 4+3's OD oil cooler tubes. They can be a major hassle to remove as they are full length hard lines that snake under the motor. If you don't need to save them, you can save yourself a lot of time by simply cutting them off in pieces and pulling them out part by part.
1) Get the car HIGH up on jackstands (the high-rise 3 ton jackstands work well for this).
2) Pull the entire exhaust off up to the manifolds/headers.
3) Remove the driveshaft.
4) Remove OD oil cooler lines, shifter linkage, and wiring.
5) Support the engine AND transmission on SEPARATE jacks or stands.
6) Remove the torque arm/C beam.
7) Disconnect the transmission from the bellhousing and remove from the car.
8) Remove the starter motor.
9) Unbolt bellhousing from the back of the motor and remove.
10) If you choose to reuse the 4+3 flywheel and clutch assembly with the McLeod TO bearing, you can skip ahead to step 16. If you choose to use the ZF style clutch, remove the clutch assembly from the flywheel.
11) If you are using anything other than the stock '85-'88 4+3 flywheel, remove the flywheel and install the new one (unless your rear main seal is leaking...now's a GREAT chance to replace it if it is
12) Install the new clutch assembly.
13) Remove stock 4+3 hydraulic clutch system. You will need to get under the dash to get the linkage between the clutch pedal and clutch master. BE VERY CAREFUL not to drop the spring clip for the pushrod!
14) If you're using the '92-up mini starter, you will need to install a longer battery cable to the starter.
15) Install new hydraulic clutch system. Be sure all who are easily offended are not present, as this step will induce high volumes of expletives (the aforementioned spring clip on the clutch pedal pushrod is a lot of fun to reinstall).
16) Install ZF bellhousing. If you are using a ZF style clutch, make sure the clutch fork is engaged with both the pivot stud AND the TO bearing before bolting bellhousing in place.
17) Install clutch slave cylinder. The pivot ball has an adjustable depth. Refer to the GM service manual for setting the pivot stud depth.
18) Ok...here's the LLLOOONNNNGGGG step. Time to go upstairs and do the transmission tunnel mods:
a) Remove both seats
b) Remove center console and transmission tunnel trim pieces to expose top and sides of the transmission tunnel
c) Remove entire shifter mechanism and bracketry from tunnel recess
d) Cut out recess from transmission tunnel. You will want to cut just wide of the edges of the recess. On the side of the recess towards the back of the car, you will end up cutting the fiberglass back to the joint with the steel floorpan.
e) Using a grinder or high speed rotary sander, you need to cut a ledge into the fiberglass....you're basically creating two tiers in the surface of the fiberglass. If possible, do this on both the inside and the underside of the tunnel.
f) take some fine mesh mechanics cloth (wire mesh) and mold it to create a smooth shape to the tunnel...you're trying to bring the tunnel back out flush with the rest of the piece.
g) I used a HOT batch of fiberglass resin to "glue" the mesh in place. Once the mesh is firmly in place, you want to apply 2-3 layers of fiberglass cloth on both sides of the wire mesh. I used 8oz cloth.
h) once the fiberglass patch is installed and cured, you want to mark the shifter hole location and cut it out. I used an angle grinder to cut the hole out.
19) Once the fiberglass patch is taken care of, the center console plate needs to be addressed. If you're reusing the '84-'88 plate, some of the plastic needs to be trimmed underneath the plate on the support structure to clear the rubber shifter boot.
20) If you're using the ZF style clutch, skip to step 22. For the McLeod TO bearing, you will need to make a -3 AN (or is it 4? Instructions included with the bearing specify the size) hose to run from the TO bearing all the way up to the clutch master cylinder.
21) Using the McLeod instructions as a guideline, remove the input shaft housing on the transmission, and bolt the TO bearing in it's place. Be sure that the bleeder hose is on top when the bearing is installed.
22) Install the transmission, making sure to carefully snake the AN hydraulic hose for the McLeod TO bearing through the slave cylinder hole in the bellhousing.
23) Install the shifter assembly.
24) Install the torque arm/C beam
25) Install the driveshaft
26) Install the starter motor.
27) Install the exhaust system
28) Reassemble interior
29) NOW GO DRIVE IT!!!
Mike
CorvetteZ51Racer did this a couple of years ago and I copied his instructions:
Swapping a ZF 6 speed transmission into a 1984-1988 Corvette involves a lot of work. First and foremost, the shifter accomodations are different between the ZF and 4+3 transmissions. Making the modifications for the shifter linkage is the most daunting part of the swap. Other than the fiberglass fabrication in the transmission tunnel, no fabrication work needs to be done: everything else is merely parts swapping.
Parts list
-----------
1) ZF 6 speed transmission out of an '89-'96 Corvette w/ bellhousing and shifter
2) Driveshaft from the same (actually, all you need is the output shaft yoke from the ZF driveshaft as the shafts themselves are the same, but they are VERY hard to find separately)
3) For the clutch setup, you have a few options:
a) stock ZF hydraulic clutch system, dual mass flywheel, and stock ZF clutch assembly
b) stock ZF hydraulic clutch system, single mass flywheel, stock ZF clutch assembly, and single mass conversion clutch pivot ball** Note: '85-'88 4+3 flywheels will work just fine. The '84 FW is too thin to use with a ZF-style clutch. Despite the fact that 4+3 clutches are listed as 10.75" clutches and the ZF is 11", it will work.
c) stock 4+3 hydraulic clutch system, single mass flywheel, McLeod p/n 1345 push-type throwout bearing conversion, and 4+3 style clutch.
4) IF your bellhousing is from a '92-'96, you will also need a new starter motor (LT1/4's use mini starter). '89-'91 bellhousings retain the 4+3 style starter motor.
5) If using the ministarter, you will need a longer (54" if memory serves...maybe 60") starter cable.
6) If possible, '89 center console plate. If you can't find one, don't stress, the '84-'88s will fit with a minor modification.
7) Fiberglass cloth, resin, and acetone.
Process
-----------
The first thing is to remove all of the 4+3 related parts. Do not forget to remove the 4+3's OD oil cooler tubes. They can be a major hassle to remove as they are full length hard lines that snake under the motor. If you don't need to save them, you can save yourself a lot of time by simply cutting them off in pieces and pulling them out part by part.
1) Get the car HIGH up on jackstands (the high-rise 3 ton jackstands work well for this).
2) Pull the entire exhaust off up to the manifolds/headers.
3) Remove the driveshaft.
4) Remove OD oil cooler lines, shifter linkage, and wiring.
5) Support the engine AND transmission on SEPARATE jacks or stands.
6) Remove the torque arm/C beam.
7) Disconnect the transmission from the bellhousing and remove from the car.
8) Remove the starter motor.
9) Unbolt bellhousing from the back of the motor and remove.
10) If you choose to reuse the 4+3 flywheel and clutch assembly with the McLeod TO bearing, you can skip ahead to step 16. If you choose to use the ZF style clutch, remove the clutch assembly from the flywheel.
11) If you are using anything other than the stock '85-'88 4+3 flywheel, remove the flywheel and install the new one (unless your rear main seal is leaking...now's a GREAT chance to replace it if it is
12) Install the new clutch assembly.
13) Remove stock 4+3 hydraulic clutch system. You will need to get under the dash to get the linkage between the clutch pedal and clutch master. BE VERY CAREFUL not to drop the spring clip for the pushrod!
14) If you're using the '92-up mini starter, you will need to install a longer battery cable to the starter.
15) Install new hydraulic clutch system. Be sure all who are easily offended are not present, as this step will induce high volumes of expletives (the aforementioned spring clip on the clutch pedal pushrod is a lot of fun to reinstall).
16) Install ZF bellhousing. If you are using a ZF style clutch, make sure the clutch fork is engaged with both the pivot stud AND the TO bearing before bolting bellhousing in place.
17) Install clutch slave cylinder. The pivot ball has an adjustable depth. Refer to the GM service manual for setting the pivot stud depth.
18) Ok...here's the LLLOOONNNNGGGG step. Time to go upstairs and do the transmission tunnel mods:
a) Remove both seats
b) Remove center console and transmission tunnel trim pieces to expose top and sides of the transmission tunnel
c) Remove entire shifter mechanism and bracketry from tunnel recess
d) Cut out recess from transmission tunnel. You will want to cut just wide of the edges of the recess. On the side of the recess towards the back of the car, you will end up cutting the fiberglass back to the joint with the steel floorpan.
e) Using a grinder or high speed rotary sander, you need to cut a ledge into the fiberglass....you're basically creating two tiers in the surface of the fiberglass. If possible, do this on both the inside and the underside of the tunnel.
f) take some fine mesh mechanics cloth (wire mesh) and mold it to create a smooth shape to the tunnel...you're trying to bring the tunnel back out flush with the rest of the piece.
g) I used a HOT batch of fiberglass resin to "glue" the mesh in place. Once the mesh is firmly in place, you want to apply 2-3 layers of fiberglass cloth on both sides of the wire mesh. I used 8oz cloth.
h) once the fiberglass patch is installed and cured, you want to mark the shifter hole location and cut it out. I used an angle grinder to cut the hole out.
19) Once the fiberglass patch is taken care of, the center console plate needs to be addressed. If you're reusing the '84-'88 plate, some of the plastic needs to be trimmed underneath the plate on the support structure to clear the rubber shifter boot.
20) If you're using the ZF style clutch, skip to step 22. For the McLeod TO bearing, you will need to make a -3 AN (or is it 4? Instructions included with the bearing specify the size) hose to run from the TO bearing all the way up to the clutch master cylinder.
21) Using the McLeod instructions as a guideline, remove the input shaft housing on the transmission, and bolt the TO bearing in it's place. Be sure that the bleeder hose is on top when the bearing is installed.
22) Install the transmission, making sure to carefully snake the AN hydraulic hose for the McLeod TO bearing through the slave cylinder hole in the bellhousing.
23) Install the shifter assembly.
24) Install the torque arm/C beam
25) Install the driveshaft
26) Install the starter motor.
27) Install the exhaust system
28) Reassemble interior
29) NOW GO DRIVE IT!!!
Mike
