I thought that I saw a post that says this is a bolt in swap. Any one out there know if this is an easy do? Love the idea of a .5 to one OD.
Thanks, FATED

It's almost bolt in. You have to cut a hole in the fiberglass tunnel and patch it though.

You won't like the idea of a 0.5 OD on your 3.07 rear end unless you plan on driving 90mph often. With that 6-speed, you'll want to swap to a 3.45 or 3.55 rear.

I have a parts list, I'll post it here later. It'll cost you about $1600-$2200 for everything to do the swap.

I have 3.55 rear end I installed about a year ago. Thanks for the response. I will be looking for the parts list.

Here's the list. So what's wrong with your 4+3?




COMPLETE PARTS LIST FOR 4+3 TO ZF6 CONVERSION:

84-85 Corvettes only:

89-93 black-tag ZF6 & 90-93 ZR1 clutch set or 95-96 blue-tag trans & 95 ZR1 clutch set
Standard Flywheel p/n: 6516 from Kragen/PartsAmerica (reusing original flywheel not recommended)


86-88 Corvettes only:

89-93 black-tag ZF6 & 90-93 clutch set or 95-96 blue-tag trans & 95 clutch set
Reuse stock flywheel or 89-96 ZF6 (dual mass) flywheel


Everyone:

91-96 bellhousing, from salvage yard

89-96 clutch fork and pivot stud, from salvage yard

88-91 starter

89-96 clutch master cylinder (recommend cast iron unit)

91-96 clutch slave cylinder (recommend cast iron unit)

91-96 clutch slave hose, from salvage yard

89-96 driveshaft, from salvage yard (or just get the slip yoke and install it on your 85-88 manual driveshaft)

TH400 rear seal, Timken #9449 (optional)

Backup switch connector, a.k.a. horn connector, AcDelco # PT1357 or Napa # ECHEC11

(5) metric M12 x 45mm transmission bolts, McMaster.com # 92820A650

(6) standard 3/8" x 1-3/4" pressure plate bolts, McMaster.com # 92316A630

17mm allen driver socket attachment (for fill & drain plugs, available at autozone/kragen in a 3-pack)

12mm allen driver socket attachment (for fork pivot stud)

3 quarts of GM 1052931 or Pennzoil Synchromesh from Autozone

Sheetmetal, rivets and sealant for patching the trans tunnel, and some extra carpet insulation.

Hurst B-4 Shifter Boot p/n 1144580 or OEM 89-96 shifter boot


For dealing with salvage yards..., refer to my part number/application guide and make sure you're getting the right stuff:

CLICK HERE

CorvetteSalvage.com and Vette2vette.com are recommended.


Beware of defective parts!

The ZF6 replacement throwout bearings are Chinese and prone to failure. Inspect the rear flange carefully before purchase for cracks. If it breaks, the car will be undriveable.

CLICK HERE

For awhile, many of the slave cylinders were defective from the factory with a backwards seal. This has since been addressed, but check anyways incase you got an old one:

CLICK HERE
CLICK HERE ALSO


Shifter Upgrade:

I highly recommend installing a Hurst or B&M shifter before installing the ZF6. They are far superior to the stock shifter but are a bitch to install when the trans is in the car.


Gearing and Vehicle Speed Sensor (speedo)

The stock 3.07 ring/pinion makes 6th gear unusable under 85mph. I recommend upgrading to a 3.33,3.45, or 3.55 ratio. This will require changing your speedometer gears.

CLICK HERE

Some background info on the VSS: There are 4 types of VSS's, "large gear" 40-45 teeth, or "small gear" 35-40 teeth, and "early" 84-90, or "late" 91-96. 4+3 owners, just install your old VSS in the ZF6. Automatic owners, you can install your "small gear" VSS upside down in the ZF6 to get proper mesh.


Push-type Clutch Options:

You can retain your "push type" clutch setup with the ZF6 if you convert to a hydraulic throwout bearing. This gives you a superior clutch setup, and more clutch options, but isn't bolt on. Check with forum member LD85 for more info. Hydraulic throwout bearings are made by McLeod, Howe and Ram.


debunking a few myths:

My 85 did not require a longer battery cable (+). The stock one is long enough. I had to tweak the end of the cable to fit the ministarter terminals and rerouted it sideways to the positive battery terminal to get extra reach. Do this when the bellhousing and trans are out of the car.

The longer ZR-1 pivot stud was NOT used. I used the regular pivot stud tightened down all the way. The fork comes close to the rear of the bellhousing with clutch out, you'll need to slide it onto the pivot stud, put the bellhousing in place, then tighten the stud into the bellhousing.

Actually nothing. I went to the 4.55 gear set for the snap but my cruse MPG is in the pooper. I was getting about 24 measured at 70 and it has dropped to about 18 MPG. With a .5 OD I should make it back.

You gave me advice on the 4+3 right after I bought the car. I replaced the transmission but kept the OD.
I also replaced the clutch complete and noted the flywheel was nearly pristine. I don't think the car was ever driven hard or abused other than never servicing the gearbox.
Is there any other reason why I cant reuse the 85 flywheel other than impending failure of the flywheel?

This is why I suggest not using it with the 11" ZF clutch:

http://www.corvette-guru.com/modules/ ... pe=&topic_id=3346&forum=1

Also the replacement flywheel I used was only about $40 after core.

Did you use a dakota digital to adjust your speedo?

I belive that is what I used for speed adjustment. It is a black box full o DIP switches that I mounted under the passenger seat.

Also, I did find some more info on the swap. After reading it sounds to me like I can use the Howe 82876 slave and an adjustable master, shim the Bell Housing and use the 85 clutch Pressure plate and disk. Is this true?

I can't help you there. Everytime I researched keeping the 4+3 clutch I ended up with halftruths and untested information.

LD85 might be able to help. I recall the Howe doesn't fit and needs shims on the bellhousing, although the 89-90 bellhousing will help, it's ever so slightly deeper.

What about cutting the flywheel down more?

I just don't like the idea of bellhousing shims. That whole thing is a weak structural member, and on the C4 especially it gets a lot of force put on it carrying the weight of the drivetrain bouncing around.

Unless your shim consists of an aluminum or steel plate that covers the entire surface, I don't like it.

I have a lot of aluminium sheet. I have some .080 and some .020 to make a full shim. I will PM LD85 and see what he says.
When I was 16 I had a 47 Harley that had a bad front sprocket. I replaced it with a non sprung sprocket and the damn thing was just about un rideable. Either the engine would die or the wheel would spin.

The Transmission I am looking at comes with the BH, PP, and CD. It is a blue tag so I may have more room then. I will have to bush the bearing cover to bring it out to 1.375 for the Howe slave.

Why not go with a richmond 6 speed. Might be cheaper in the end?

If I buy the parts Im looking at I can bring this in for less than 1800. If I don't think I can do it for that I will probably stick with my 4+3.

Don't be concerned about clutch engagement with a non-sprung disc on a 1-pc flywheel.

It's a non issue.

And by non issue, I mean you will not know the difference. I have zero problems with clutch engagement on the street or track now that I've got the right combination in there. It drives like you'd expect it to straight from the factory.

In fact if anything the sprung 4+3 was worse. At very low rpms I would sometimes get bucking in 1st gear, probably due to the sprung hub.

I can't speak for aftermarket clutch discs, but the only complaint I've ever seen is the same gear noise, and the few that put sprung hubs on a one piece flywheel didn't report an improvement. If a sprung hub killed the gear noise, GM would have used it.

Just so I have it straight, if I use a flywheel that has been ground flat on the clutch side, like the Kragen 6516, I can use the ZF clutch disk and pressure plate ?
More or less the whole ZF setup?
I can get the flywheel for about 50 bucks and if the non sprung hub is not a problem Im good to go except for a slip yoke, starter, hole cutting, and plumbing.

You got it.

Other than the noise, the other downside of the ZF is the low quality clutch components.

Whatever you do, avoid the DOM (smooth, thin, black powdercoated) clutch cylinders like the plague. They use aluminum pistons which will corrode the hell out of the steel cylinder walls.

Buy cast iron ones instead. These have steel pistons, although the seals aren't quite as good so you may get a little more weepage over time, but overall it will last longer. I already destroyed one trans from a bad clutch master, I don't want to do it again. Also the reservoir caps on the cast units suck, reuse the rubber boot from your 4+3 master.

And I don't like the throwout bearing setup, they are prone to failure and defects so inspect them carefully before installing.

All of those parts mentioned above are made in China. But in this case you don't have a choice.

Does anyone know the PN for the slip yoke that fits the ZF6? Is it SY-1310-3550 ?
Regards,

It doesn't have it's own p/n seperate from the driveshaft. Unless you happened to find some sort of TH400 yoke that fits the spline and ujoint.

Does a 1.172 X 27 spline 1.5 " seal sound right? Seller clames it to fit ZF-6.
Another question, what about reusing the 85 master clutch cyl?
Regards,

You can use the Howe TOB, I had to shim my bell housing @ .165" I just went to Home depot and bought .055 thick sheet metal and traced a line from my bellhousing and cut the shims, and stacked 2 of them combined with the shim that comes with the stock BH.

You will have to remove a bolt from the face of the ZF and put a longer bolt in that will prevent the Howe from spinning.

I bought a Wilwood master, get the same bore as you have now, I bought a 3/$ bore and it is a little more stiff than the stock 5/8" bore it will allow you to adjust the stroke and you will need a , once it is set, you will need to bolt on a clutch pedal stop.


You can read about it here Howe Install,, but if you have questions, post them here.

Edit, measured my shims today it is .165", you can buy two .090" mid motor mount plates from Summit for $37. each if you want to buy the spacers with holes already in them

Got my tranny out, if you need measurements, let me know.

Shim = .165" thick

Any dimensions I will probably take myself when the time comes.

I got the transmission, clutch Assy. and bell housing for $1250 so if all the parts are as good as they look, it should be a low cost swap. I will also be changing out the engine at the same time. I got a 2 piece seal crank so I could re use my 85 4+3 flywheel. So much for planning ahead. Looks like a 1 piece seal would have given me a few more options.

It seems that I have about all the parts to do this either way. Right now I think I will go the Central Coaster way and use the surfaced flywheel and all of the ZF stuff. Coud change my mind later. The only real issue I can see with that is the TOB.

I was curious as to why a smaller master Cyl. coldn't be used to cure the issue of the TOB blow out on the push install?

I really apreciate all of the info I have got from you folks.

Regards,

FATED: I was curious as to why a smaller master Cyl. coldn't be used to cure the issue of the TOB blow out on the push install?

The blow out is caused by the spacing issue, if your HOWE has lets say .549" of stroke, and it takes .375" to disengage the clutch, then it only leaves you @ .125 of travel before the piston can pass the O-ring that holds the fluid in the TOB, if you account for your air gap of @ .174", then you are on the hairy edge,,,the HOWE 82876 only has .549 of travel and I used this TOB because of the lack of space available between the clutch fingers and the tranny face, but if you space the tranny back by using spacer or a thicker bell housing, you could use the HOWE 82870 that has .789" of travel and you would be less likely to blow the piston past the O-ring.

McLeod #1345 Push/ TOB has a stop so that the piston will not come off, but the #1345 cost $350 for the bearing and you still need to necessary spacing.

Also, I found this to use for spacers, I think I will order it and throw my 3-piece stack up in the trash. I'll buy some longer dowel pins as well.

MOROSO 62595 - $47.00

O.K., let me ask dumber questions. Could the nose piece be machined down to clearence? I think I am going the way of Central Coaster so this question is kind of a "what if".
My original inclination wasto use the Howe 82870

What nose piece do you mean?

You mean a shorter trans snout in order to have more room for the TOB?

I think you remove that snout to put the hydraulic TOB on there.

LD?

Quote:

No it slides ontop of the sleeve, I'll post a pic of what I have since its on the floor right now.

That is just what I was thinking if you cut .165 off of the bearing cover snout (or whatever you might call it) you would not have to shim, maybe huh? Unless the TOB bottoms out aginst the transmission. Just wondering.

No, the sleeve on the ZF stays where it is, to take off .165 or whatever amoutn, you would have to reduce the stack/compressed height of the HOWE, which I looked at and it can not be done.

Quote:

Now you are correct that the McLeod 1345 does indeed replace the sleeve

The pic makes it all clear. Thanks for the info.

What's stopping you from turning that snout down by .165 so the Howe can sit further towards the trans? I think most of the aluminum on the face of the snout it is just web-type reinforcement for the casting.

The sleeve flange is cold formed thin gauge steel and the flange part that goes onto the tranny is not solid. Also, it exposes a bearing face behind the flange, also, the sleeve helps for the HOWE to stay concentric with the spinning PP fingers.






Thats why the McLeod is nice, you actually use that space for the base of the piston housing

At the risk of raising the boredom factor, the Howe 82870 is 3/4" thinner when compressed than the 8288 and has about 1/2" more throw. It seems like the BH shim would not be required and you would have more travel before over extension.

All of this because I still don't know for sure which way to go. They say indecision is the key to flexability.
Regards,

You can always do a push type later, your best option is to get a Single Mass FW (@ $390) , and the ZF Clutch (@ $390)

The McLeod #1345 TOB is @$400 and the push type clutch is @ $250 for a stocker and $300 for a Centerforce DF clutch and @$200 for a stock FW , plus @$30 for ss braided lines and "if ou need a Bell hosuing spacer, the cost would be $37-$47 dollars.

So the cost is @ the same, your choice,

So nice of you to take your trans apart and snap pics for all of us.

Quote:

From the time i jacked it up to washing my hands was 2 hrs 15 minutes,,, pretty pathetic if you ask my wife

You mean pathetic that you've had that much practice at it?

It still takes me about 8 hours for a full clutch/trans swap.

Quote: yes

Installed the ZR-1 clutch, machined flywheel, and 89 hydraulics. Son depressed clutch and I could turn the rear wheel over easly. Must work.

Keep us posted!

Quote:


The ZR1 stud (you sent me) has worked well for me. The aftermarket flywheel I used is singlemass and roughly 3/8" thinner than the dual mass. The ZR1 stud is roughly 5/16" taller. Geometry ended up being the same as stock, and the clutch grabs about an inch off the floor.

More than one way to skin a cat for sure.

My aftermarket flywheel is very similar to the 4+3 part that you had trouble with:

http://members.cisdi.com/~anesthes/f-car-t5/flywheel.jpg

However, I'm using a ceramic clutch from fort wayne (similar
to the one pictured below) and I think the 'buttons' are spaced far enough inside that it doesn't overlap like the stock clutch did:

http://members.cisdi.com/~anesthes/zf6/fw-zf6-kevlar.JPG

When I was in Florida last week, I spoke to a guy with a '94
for a bit. He was using a fbody LT1 flywheel, with a sprung LT1 disc and ZF6 pressure plate. I was confused as I've read the LT1 flywheel needs to be machined as much as .080" to work. When you think about it, .080" is only about 5/64".

Stock fork to slave distance is 1.438"
4+3 flywheel and stock stud is 1.230"

So reducing flywheel by .375" reduces distance by .208

So I'd imagine a .080" increase would barely be noticable to the slave cyl (about .144" increase) So why are people cutting these flywheels??

Unless my math is wrong, you would think for a 1pc rear car the LT1 flywheel and sprung disc is plug and play.


The ZF6 flywheel is 1 7/16" thick

Whats the LT1 fbody flywheel?


-- Joe

Well its interesting to me that you can use a Flywheel, that is 1/2 the cost of the single mass or 1/3 the cost of a dual mass Flywheel,

Using the ZR1 stud is a good option for as long as they last, since the longer pivot Studs are discontinued, this option will only last so long

And today, I was told by Carolina Clutch that the thicker ZR1 Pressure plates will not longer be thicker than the standard PP and that Valeo is no longer making them, I don't know if this is possible but this is what I was told.


I am very tempted to buy the McLeod 1345 Push type TOB and reverse engineer it so there would be no need for Block spacers, my brother runs a CNC lathe where he works and this type of work is gravy for him, he works in very, very tight tolerances on exotic metals so this would be sleep walking for him.

McLeod tech tells me that the 1345 is a "non-mover" so McLoed will not spend another minute trying to improve this TOB

Fuck! That sucks. At least when the part is discontinued I can get store credit on my lifetime warranty.

Quote:

I really would like to find out what the actual measurement is of the LT1 fbody flywheel. I know it doesn't help folks with 2pc rear mains, but I'm curious where this whole milling .080" off came from.

My unsprung, singlemass setup drives fine but the noise is a little lame. When we had the car on the dyno a few weeks ago the operator thought it was going to explode.

-- Joe

Quote:

Probably the same place all other free internet information comes from. Spoken once, regurgitated 5,630 times, and questioned never.

Quote:

Figures.

-- Joe

Well, if youy have the ZR1 stud, you are OK.

Just thought that I would try the starter before I took it off of the jack-stands. No starter. I had to use a 1/4 inch spacer instead of the 3/8 inch. This put the starter lock out switch out of adjustment.
I am going to think about this for a minuet then just bypass the damn thing.

O.K. I drove this thing around a couple of blocks. This thing is incredibly noisy. I am going to look for some other source of the noise but I don't know what it could be. At first I thought that valves were bouncing off of the pistons,(new engine too), but then realized it was coming from some where else, after changing to stock rockers and adjusting valve lash until I was nauseous. Decided to go with the blow it up and do the autopsy route. Engine runs fine and noise go's away at 3000 turns/ 30 mph 2nd gear. Also put header wrap on with the high temp paint sealer. Caught fire. Little damage, going to jack it up now and check it out. Peel off the header wrap too.
Thats my update for now.