Hydrolic throw out bearing conversion concerns...

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darkhorizon
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Hydrolic throw out bearing conversion concerns...

Post by darkhorizon »

Got my 94 sunbird bellhousing, brand new htob, brand new clutch and spec alum flywheel...

took some measurements:

surface of trans, to fully retracted htob = 2 5/16

Surface of PP fingers to block mating surface fully installed and torqued = 2 11/32

Surface of PP fingers to block mating surface with .090 inch spacers on the PP to flywheel to simulate wear = 2 7/8

Distance from flywheel friction surface to block mating surface, 3800 = 7/8

Distance from flywheel friction surface to block mating surface, stock 2.8 = 13/16
Last edited by darkhorizon on Thu Jun 12, 2008 12:57 am, edited 1 time in total.
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Series8217
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Post by Series8217 »

.9 inch spacers to simulate what wear? The clutch doesn't wear more than a few tenths at most. The pressure plate and flywheel wear can be measured in hundredths.
darkhorizon
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Post by darkhorizon »

oops, mistyped that wear number, it was.090.
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Series8217
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Post by Series8217 »

Where are you putting the spacers? I don't think the rate between the pressure plate friction surface and the fingers is not 1:1. I'm not exactly sure what it is though.

Do you know the distace from the mating surface of the regular GETRAG to the standard throwout bearing when fully retracted?

EDIT: Why didn't they make the flywheel have the same offset as the 60* from the block, since its only being used for Fiero conversions anyway?
darkhorizon
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Post by darkhorizon »

Series8217 wrote: EDIT: Why didn't they make the flywheel have the same offset as the 60* from the block, since its only being used for Fiero conversions anyway?
I think its close enough to assume that it will work, as far as the flywheel thickness goes...

Those spacers let me see how far the fingers stuck out when the disk is worn. I would imagine for that measure ment to be correct you would have to remove like 1/10 to space the PP back in.. but I could be mistaken.

Either way, I know that the fingers will start to stick back into the HTOB, a significant distance
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Post by The Dark Side of Will »

That's strange.

phpBB/viewtopic.php?t=3376

I measured 2.25 total engaged stack height on my Centerfarce clutch, which would work with your measured distance from the bellhousing surface to the HTOB.

2 11/32 sounds a little bit high for that dimension.

Has your 2.8 flywheel been resurfaced?
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Re: Hydrolic throw out bearing conversion concerns...

Post by Kohburn »

darkhorizon wrote: surface of trans, to fully retracted htob = 2 5/16

Surface of PP fingers to block mating surface with .090 inch spacers on the PP to flywheel to simulate wear = 2 7/8
so you are trying to fit a clutch into a space that is 9/16 " too small?
darkhorizon
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Post by darkhorizon »

The Dark Side of Will wrote:That's strange.



Has your 2.8 flywheel been resurfaced?
I am going to say its a OEM 88 flywheel I know it has had very few miles on it.
which would work with your measured distance from the bellhousing surface to the HTOB.
It would work, but it would offer almost no wear expansion...
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Post by The Dark Side of Will »

The CF already had quite a few miles and a LOT of launch practicing on it at that point. I don't have the disk thickness, but it was already pretty worn.
fieroguru
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Post by fieroguru »

Are you sure you have the right hydraulic throwout bearing? On my original 93 Getrag, the distance from the bellhousing face to the HTOB is just over 2 3/8" vs. your 2 5/16"
Image

From my records the last time I messed with a stock 2.8, the distance from the engine bellhousing to the furthest part of the pressure plate is 2.368" with .830" being the distance from flywheel face to bell housing.

What pressure plate are you using? I have installed 3 specs with the HTOB setup (stage 2+, stage 3 and stage 3+) and on everyone of them the pressure place fingers did not stick out further than the pressure plate rivots - even when you provide for wear.
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Post by The Dark Side of Will »

I just spoke to Christian. I had to unseat the input bearing in that transmission to get the bellhousing to sit flat on the mill table. Reseat the bearing and then take another set of measurements.
darkhorizon
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Post by darkhorizon »

Its already sitting fairly well from what I can tell on the bell housing surface...

What do I have to do to get the input shaft bearing pressed down more?

The HTOB looks quite different from the one in the picture there... I have a "shoulder" that sits sorta inbetween everything... I have a feeling that might be the kicker here.
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Post by fieroguru »

Here is another couple of pics of the HTOB for the 93 Getrag:

Image

Image

There are several versions of these: 92-94 Getrag, 95+Isuzu and later model Getrags... might have just been packaged wrong.

Notice the blue seal hanging out... that's what happens when you exceed its travel and the piston comes out of the bore (no snap ring to keep it together).
darkhorizon
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Post by darkhorizon »

So in your picture you are FULLY compressed? Ours is 47mm high sitting flat on the table, aka 1.85inches. making it .17 inches shorter than ours, and you used a carpenters tape along with it possibly not being perfectly flat.. so minimum it is .17inches shorter. If it was 1 1/16 shorter it would put us into the perfect range of the extra 1/4 of clearance we are looking for right now.

Christian is convinced the flywheel is too tall, but the 1/16 or less that it is too tall is nothing compared to how far the system is actually off by right now. If I had your exploded HTOB I would have about .12 inches of clearance between the face of the htob and the fingers of the PP, right now they are near perfectly interfaced.

As far as the inputshaft bearing goes... It may be incorrectly seated but it has little to no effect on the HTOB figment at the moment.
darkhorizon
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Post by darkhorizon »

just talked to rhinopac, the makers of the HTOB we got.

He walked me through some steps to check the tolerances of some things, really knowledgeable and helpful guy. I had him look up any other HTOB that would even pretend to work with ours, and he said that the one he had listed for a quad and 95+ motor was 2 or 3mm shorter than the one we had. The line config was similar also.

On rock auto they list this

BCA/NATIONAL Part # 619005 More Info {Ball Bearing Bore=1.2" Outer Diameter=3.23" Width=2.676"}
Hydra-Clutch®; (NVG T550) (5 Speed)

thats 67mm high aka 5mm shorter than what I have.... and significantly larger in diameter than the one I have. my bearing bore is .9, and my diameter is 2.9..... ugg this is so confusing!!
Last edited by darkhorizon on Fri Jun 13, 2008 11:52 am, edited 3 times in total.
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Post by Atilla the Fun »

I have nothing to add, but I want to thank all of you for all of this, as I may find something helpful for my own project.
darkhorizon
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Post by darkhorizon »

Now I cross listed the new "shorter" ones that they say they have, and found a few "95 specific" ones by raybestos.

NOW I find a izusu throwout for a 95.

BCA/NATIONAL Part # 619006 More Info {Ball Bearing Bore=1.9" Outer Diameter=2.9429" Width=1.5583"}
Hydra-Clutch®; (Isuzu 5 Spd.)

same exact bore and outer size, but MUCH shorter than both of ours!!!

It was listed next to this 1761 rhinopac that the rhinopac guy told me was a bit shorter. I have a 1756 here right now.
darkhorizon
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Post by darkhorizon »

I found a AC delco picture, listed for the 95 transmissions, and it measured the 43mm based on counting pixels on the picture.... dont really know if that means anything....

I am completely lost here.... What replacement part did you get guru?
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Post by Nashco »

Similar to Attila, I have nothing to offer but this is really good info. I started to look into a HTOB long ago and decided it wasn't worth the hassle with a stock clutch, but when doing custom clutch work in the future this will probably come in handy. Good work.

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Post by fieroguru »

darkhorizon wrote:So in your picture you are FULLY compressed?

Christian is convinced the flywheel is too tall, but the 1/16 or less that it is too tall is nothing compared to how far the system is actually off by right now.

As far as the inputshaft bearing goes... It may be incorrectly seated but it has little to no effect on the HTOB figment at the moment.
In the pick , there is about 1/16" from the plastic base to the metal flange right below the bearing face, so it could be possible that a piece of a seal is stuck keeping the bearing from going down some more. I have a non-exploded one on the shelf that came with the used tranny, but I am currently 350 miles from there. I can check in when I get back on Sunday.

If the flywheel is 1/16" further from the engine, that is part of the issue. Sure you might be able to find a shorter HTOB, but the available stroke will be reduced by about twice the difference in height (base and piston would both have to be shorte). If these things had a snap ring to keep them from self-destructing if over extended, it would be worth a try. However, they don't and if you go too far you will destroy it and will be out 100 to 150 for a new one.

It has been several years since I looked into this, but I thought the Getrag was in hiatus from 1995 to 2000 and GM used the isuzu during these years. If this is the case, then the 95 HTOB you have is for an Isuzu tranny.

Another reason just getting a shorter HTOB might be an issue is the depth of the flange on the ID of the HTOB - this is very close to resting on the input bearing face. A shorter HTOB was most likely designed around a shorter protrusion of the input bearing face to the base of the case. So there is a chance that a shorter HTOB will hang up and not be fully seated and not give you the room you need. I would siggest you double check the depth of this inner flange and the protrusion of the input bearing face to see if that isn't an issue right now.

Everything I have seen shows this generation of the Getrag from 92-94, but not all of them had the HTOB. It has been several years (and I do not have my notes with me), but I though the FWD GM Getrag was in Hiatus from 1995 to 2000 and that they only ran and updated version of the Isuzu during those years.

My thread on Old Europe lists all the measurements and links to the part #'s I used in my swap with the 1992-1994 HTOB Getrag:
http://www.fiero.com/forum/Forum2/HTML/091336.html

I suggest you start with the right HTOB for the tranny and go from there.
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