Just a thought about adapter plates

[redhat-z]

Of all the people on here putting a manual transmission behind a VH, does anybody actually measure the runout of the crank centerline to the input shaft centerline. As you all know, the repurcussions of not doing this could be pretty severe. When I made my plate, I almost scrapped it and started over because I couldn't get the runout on centerline less than 0.006". After a little convincing, it is down to 0.003".

I just hope everyone is assuring this on their own vehicles.

[elwesso]

Do you think that with some of the thinner plates that maybe it would sort of self-correct when you tighten everything down? Probably more so with steel than aluminum.

[SuperHatch]

Do you think that with some of the thinner plates that maybe it would sort of self-correct when you tighten everything down? Probably more so with steel than aluminum.

Absolutely not. The alignment is mainly a factor of the location of the dowel pins, it has less to do with the bolts, and nothing to do with the thickness or material.

[Mettler]

How are you measuring this accurately?

[redhat-z]

I used a "Last Word" dial indicator positioned on the crank and my plate has a CNC'd center register bore that is aligned with the crank centerline. This is nothing new and is suggested practice with the fitment of almost any modified bellhousing.

[T45]

6 thousandths is nothing IMO, but I'm used to working on big boats and reduction gears. Maybe .006" is a lot when the parts are smaller. Even still, I'd be curious to see what kind of runout a stock assy has.

Even with the runout, the pilot will make sure it's centered in the crank, and as long as the plate is flat I don't see a big issue. I could be wrong though...

[SuperHatch]

Even with the runout, the pilot will make sure it's centered in the crank, and as long as the plate is flat I don't see a big issue. I could be wrong though...

Right, but when you torque down the bellhousing it will preload the input shaft to whatever direction the engine and trans are misaligned to. Once that happens, you will see seriously increaded wear to the input shaft bearings and possibly the main bearings in the motor.

[T45]

I can see that theory, but with a bronze pilot bushing in there it will wear down in a matter of seconds if there is any dis-agreement between the crank and shaft. That's it's purpose.

I'm not saying that is a good thing because it will still be off-center, but if it's off by that much then you would probably know because getting the bolts started and pilot lined up would be a *****.

[SuperHatch]

I can see that theory, but with a bronze pilot bushing in there it will wear down in a matter of seconds if there is any dis-agreement between the crank and shaft. That's it's purpose.

I'm not saying that is a good thing because it will still be off-center, but if it's off by that much then you would probably know because getting the bolts started and pilot lined up would be a *****.

Even if they wear to a point of "agreement", with every degree of rotation they will disagree again. The clutch disk is connected to the input shaft and the pressure plate/flywheel are connected to the crankshaft.

I'm not trying to argue, I just need to be clear that this is a big issue, not something to be taken lightly.

[T45]

We agree to agree. I'm not arguing either. It's just bad to have mis-alignment of the shaft with clutch disc/flywheel assy. If off by a lot then over time it will wear out the bearings in both engine and trans.

I can't see .006 causing massive wear, that's all. Most transmission's with 100k on them probably have that much play in them anyways.

[ultrapulse]

It also depends on what type of box you have. A zed box or w toyota, like most, has a high clearance bearing on the input shaft. However my T56 has a tapered roller setup meaning the shaft dont wanna move any noticeable amount from centre. Any misalignment is obviously not good, but I would try and make it more like half this for most gearboxes. Mind you I hate crap jobs and are quite fussy. Back with my first attempt (and less experience and/or workshop space) I made a bellhousing to mount a w toyota box upto my holden 202 and it was prob out by 6 0r 8 thou ata guess. The box took ages to get noisey and I did skids left right and centre. These days though I like to know it's right.

[SuperHatch]

We should also keep in mind that even though a trans with a high clearance input shaft might not mind 6 thou, a properly set up "factory" VH has around 1 thou clearance on the mains, with 2 thou being the limit. Granted, I'd aim for 2 thou on a performance build, but that's not the point.

I guess the concensus is that it is important...

[T45]

Like I said earlier, I'm used to .010-.005 being pretty much perfect so maybe I should be more concerned with even lower tolerances on smaller machines. .010 on a 2 ton 10 inch shaft doesn't really affect it that much. lol I'm learning as we go...

Not to threadjack here but just to put it into perspective of what I'm used to...

Here is a gearset that moves the railway at the shipyard I used to work at.



Here is an 16 cyl on a dredge. That plywood is about 2X3 ft and there is a coffee can on the table to get a size perspective. The valve covers are just below eye level. Notice the monster turbo and huge twin air driven starters.



Here is the pump on the dredge that is connected on the other side of the bulkhead of that engine. The engines do double duty, turning the prop/wheels and the pumps. It's a big *****. Size can be felt by looking at waterhose hanging on wall, it's about 10 ft high and I believe the piping is 24".

[ultrapulse]

Cool, big boys toys.Back to the point, it also obviously depends on the runout angle, ie how long the shaft is from one bearing to the next. With say only 6 or 8" from the input bearing to the spigot bush in the crank meaning quite low numbers. In saying all this I have never actually measured a factory setup..as in a bellhousing thats been unbolted, possibly dropped, heated and contracted for 20 years:) Mind you the VH4x bellhousings are extrememly thick and well braced, and approx 3 x thicker and much more bracing than the GM C5 vette bellhousing my gearbox cam with...

[ultrapulse]

How are you measuring this accurately?

I can at least measure accurately on a 45 as I still have the dummy shaft and my block in bits. I'll be realigning my spare z32 box next time I have it out as the workmanship of the original job looks a bit crappy.Here's some pics of what I used to measure it. The dolly bush in the input bearing space is what I used to locate the box to sort the dowels out.

[ultrapulse]

Come to think of it this dummy shaft will also work on a 41:)