BTDT. It's *not* a pilot bushing. That is the crank. Kind of embarrasing how long I banged away with grease and a machined plug to fit the hole before I figured it out <img src="/forums/images/graemlins/scared.gif" alt="" /> I also asked about it on clubgp afterwards and they confirmed that's not a bushing.

Was your 3800 from a automatic f-body? I would've guessed the manuals (if they came that way at all) will have a bushing, but maybe not.

--Dan

If I put the clutch disc right at the end of the transmission input shaft, just as the input shaft splines start to taper and match that where the clutch hub splines start to taper, My clutch disc is .5" away from the flywheel.

Both sides of my bellhousing have cast flanges of .5", so if I take .25" off each side of the bell I get my .5"

So should I just go the full .5" 50/50 on the bellhousing, cheat the clutch disc forward off the splines about .1" or so and do .4" split or what? Mill the engine mounting surface more/less than the trans mounting surface?

I was even looking over at the mounting surface of the transmission since it has a thick .65" mounting flange thinkness. Think a machinst can stand the trans upright in a machine to mill it? That way I can split the .5" divided by 3?

Besides concentricity, spline engagement is one of the few things you can't easily tweak or cheat. <img src="/forums/images/graemlins/frown.gif" alt="" /> Pilot engagement is cake, compared to this...

Removing a half-inch from the bell seems like too much -- I'd not want to knock the flanges down to a quarter inch thickness. For reference, my McLeod bell housing is quarter-inch hydro-formed steel and is overkill, but I'd want more aluminum than that, especially since it is cast. I suppose you could build-up the backside of the front flanges with weld, and you could true up the surface just fine as long as you kept the rear face of the bell unmolested. If you do this, I'd pile on the aluminum only after bolting the bell to the back of the block (got a core motor handy?) to minimize heat-induced movement.

A machinist could easily work the front face of the transmission housing, but that's non-trivial disassembly to get to the bare housing, and you'd have to be careful to mill only those areas where the bellhousing attaches and not where the input bearing retainer attaches. Do-able, but not simple.

IMHO, look to the clutch disk itself -- do you have an old clutch disk that you can take apart? The female-splined hub around which the friction plate is built is generally connected in front of the disk...

Alignment between the flywheel and pressure plate prevents you from just flipping it and running it backward, but a custom clutch house should be able to reman your existing friction plate with the hub behind the plate, and perhaps even a spacer... hard to say what's involved without taking you clutch disk apart. Finding a shop that will do this won't be particularly easy, but I am certain that they exist, as you can get just about ANYTHING rebuilt that has friction material on it, and many industrial applications are one-off deals, where you take them in the old one and they rebuild it. Hit the yellow pages for the closest major metropolitan area -- this a dirt-under-the-nails industry that isn't likely to have much of an internet presence... a clutch CHANGE shop won't be able to do this (they just order parts, and do no rebuilds), but they might be able to refer you to a vendor who can.

IMHO, first see if you can find a friction vendor to set you up -- changing that piece should be cheaper than machining two sides of the bell plus possible the transmission, and it should have least impact on potentially creating intereference inside the bellhousing. If you can't make that work, build up the thickness of the front flanges of your bellhousing, and you'll only need to do one setup at the machinist to scalp the front face where it meets the tranny. Tweaking fron and back of the bell AND front of the tranny is gonna be three distinct setups, which will cost you enough that shortening and cutting custom splines into a longer input shaft may begin to make sense...

Thinking on this sort of stuff is MUCH more fun than cleaning my shop!

Randii

And just think, you'll shave an extra 1/2" off your driveline while you're at it, allowing you an extra 1/2" of rear driveshaft.

Maybe this is helpful. Here's a pic of some input shafts from Marlin's shop. The AR5 input shaft is on the far right. The 96 and Later R150F input shaft is in the center. Marlin made the AR5 input shaft fit into Mike Woods R150 but I'm not sure what version of the Toyota tranny he used.



Looks like it's got just enough UMPH to make it work.

This info from Marlin's board:

"Isusu chose to use a rearward pull clutch so I had to modify a Isusu front nose cone and the Toyota input to accept the larger 1 and 1/8" Toyota input shaft. I had to use the 96' and newer R150F trans with the longer input gear and extend the pilot tip as well. My extension slid into the factory Isusu pilot bearing.
Because the newer input gear does not mesh with the older (86-95') countrshaft, (greater helix angle), I was unable to use the 4.31:1 R151F trans
Yes, I used a 10.5" Toyota disk made by centerforce for the chevy V6, V8 converson.

I am doing this from memory, it has been a couple of years since I did the two conversions.

Marlin"

Oh the joys of fitting together non-stock parts!

Greg

So I am still looking for a way to bring my input shaft .5" to my flywheel. The Aisin transmissions cannot swap input shafts with other models if they are of a different first gear ratio. So swapping to the longer Isuzu AR-5 input shaft is out.

I called around on having a custom flywheel made and this is looking like a $450-500 solution.

I also called around some clutch resurfacing shops and they had never heard of changing a clutch offset so I think a custom clutch is out too.

I think I am down to a flywheel spacer/adapter. This is just a draft , with no real measurements. Holes are just for illustration for now.





This will push the flywheel out .5". It will have a snout on the crank side to center it, and the other side will support a Toyota pilot bushing so I don't have to get one made. Pics are from emachineshop.com and their software.

This will still leave the problem of starter engagement and my bolts will have to be .5" longer so there might be some more stress here. Not sure if I this would be a problem.

That Isuzu bell is stout (never noticed how thick those flanges were!), but is also pretty difficult to find... IIRC Marlin ordered the ones for Michael and Corbin's trucks straight from the dealer. I'm surprised that the friction shops can't help?

The flywheel space/adapter seems like the cheapest option, if you can really get one for $135 (I'd have guessed $300, myself - and I'd be fine with aluminum in this compression application). I'd separate the pilot bushing and spacer for less cost and complexity.

The spacer could be as simple as a flat donut to fit around the little stick-out of the crank bore, with the holes drilled... you'll need less material to do a flat, mostly 2-dimensional donut than the more 3-dimensioned setup you show. It should also save you on machine time for hogging through waste, and less operations should be cheaper, as well. Machine list could be as simple as:
1.) start with 1/2" aluminum flat plate, chucked up on lathe
2.) turn OD round to same dimension as crank OD
3.) turn ID to knock out a center hole a bit larger than the pilot bushing
4.) turn a larger ID about half-deep to fit the OD of crank shoulder stickout
5.) (optional) light cut to face the workpiece
6.) (optional) cut a slight reference groove where the crank bolt hole centers are located
7.) flip the workpiece, chuck it back in
8.) face the piece down, but leave a short shoulder OD for the flywheel to engage
The bolt holes themselves could go in with a mill for perfect balance, or could be dropped in at your end with a drill press, using the flywheel as a template. Drill 'em just a hare oversize to permit radial hole misalignment -- the shoulders on the crank and adapter are what lines things up, the bolts just clamp it all together. You'll need to factor in the cost of longer flywheel bolts (you want quality fasteners here), which may be a bit of a pain to source. You could start with a thicker plate, it just depends on what stock they have and how much material you want to play to remove... I think half-inch plate would be good enough, even narrowed a bit when you provide for the shoulder.

Starter line-up will be easy if you find some negative shims. <img src="/forums/images/graemlins/pfft.gif" alt="" />

Randii (who still likes the custom friction plate)

I edited my above post to remove that as an option for clarity. <img src="/forums/images/graemlins/frown.gif" alt="" /> The AR5 bell won't bolt to my engine, mistake on my part.



The places I called said they would drill out the old rivets and replace the friction surfaces. No one would touch changing the design of the disc itself. They said it would require hardware to act as a spacer and they wouldn't provide it or help design it.



If I get rid of that big projected piece and change to 6061 Aluminum The price drops to $100. The drilled holes are only a $5 difference so I kept them in versus doing it myself. I'll revise this with real dimensions and post pics.

About starter shims. If you shim the starter, doesn't that just push the starter down? This is the type of starter that has two vertical bolts, no horizontal alignemnt adjustments that I see.

Ok, this is a total hack, so take it FWIW...

You could make your spacer .5" less the thickness of a flexplate that'll bolt to your engine. Put the flexplate on, then the spacer and then the flywheel. Use the flexplate so you won't have to move the starter.

Flexplates are pretty light, but if anyone gives you crap, just tell them it's one of those custom flywheel weights for making it crawl at low rpm better. <img src="/forums/images/graemlins/wink.gif" alt="" />

--Dan

I wonder... how much movement do you get of the actual friction surface if you remove it and reposition it on the opposite side? Consider that you also might be able to reverse the splined piece AND replace the rivets... the aggregate change might get you close enough to just mill the back of the bell. Measure up a storm on the disk -- that may be the cheapesy and easiest option.


Whoops. I was think of starters that bolt to the front face of the bell, with the bolts parallel to the crank. 'Negative shims' are a bit of a joke (apparently a poor one!) -- think about it, wouldn't it be handy to be able to 'shim' a 31" door into a 30" door frame? <img src="/forums/images/graemlins/pfft.gif" alt="" /> Antimatter shims?

Randii