Muncie insights

Real tech discussion on design, fabrication, testing, development of custom or adapted parts for Pontiac Fieros. Not questions about the power a CAI will give.

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crzyone
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Re: Muncie insights

Post by crzyone »

Yeah when I started reading this yesterday I was like "oh, I haven't seen him on in a while" to all the old user names then I saw the dates lol....
The Dark Side of Will
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Re: Muncie insights

Post by The Dark Side of Will »

Lol... Yeah, I was putting a 282 together for a customer and needed to dig up my notes on how the shim selector tool actually worked.
pmbrunelle
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Re: Muncie insights

Post by pmbrunelle »

The 2nd gear tooth counts are in the initial post, but since my Muncie is currently apart, I decided to count all of its gear teeth and document that for future reference.

M19 Gearing

Input Shaft
1: 15
R: 12
2: 22
3: 37
4: 47

Idler Shaft
R: 29

Output Shaft
Final: 21
1: 53
R: 41
2: 43
3: 46
4: 38

Differential
Final: 86
Planets: 15 (I believe that the exact same gear is used on the Fiero Getrag 282)
Satellites: 11 (I believe that the exact same gear is used on the Fiero Getrag 282)
Last edited by pmbrunelle on Tue Sep 28, 2021 12:29 pm, edited 1 time in total.
The Dark Side of Will
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Re: Muncie insights

Post by The Dark Side of Will »

Snazzy.
pmbrunelle
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Re: Muncie insights

Post by pmbrunelle »

The Dark Side of Will wrote: Mon Jun 19, 2006 6:57 pm Shift shaft seal: 3667
I used the National 3667 for my transmission rebuild. However, I noticed that it wept oil from the shift shaft seal.

The National 3667 is meant for a shaft dia. of 0.690", according to the specifications on the Rockauto information pane.

I measured my shift shaft and it's about 0.550". Looks like the hole on my present seal is a bit big.

SKF 5606 is also listed on Rockauto for the Fiero Muncie.

The SKF 5606 is meant for a shaft dia. of 0.563", according to the specifications on the Rockauto information pane.

I have ordered some SKF 5606 seals, and I will see if they seem like a better choice.
pmbrunelle
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Re: Muncie insights

Post by pmbrunelle »

pmbrunelle wrote: Fri Oct 08, 2021 3:04 pm I have ordered some SKF 5606 seals, and I will see if they seem like a better choice.
That's what I ended up putting on my Fiero, but my car is hibernating for the winter. Ya know, crystallized water everywhere :wink:

********************************************************************************

I was wondering about the concept of selective shims and preload... (not a discussion specific to the Muncie, but anything similar with tapered roller bearings and shims)

It seems like the idea is as you draw the case halves together, the aluminium case halves stretch a bit, and then you hope that any further length variations that occur in service can be absorbed by this stretch, hopefully avoiding play.

So the input shaft and countershaft are parallel and close together, such as 76 mm apart. Lets not discuss the diff bearings, which are in a faraway continent.

What happens when one shaft is shimmed longer than the other shaft? Is it possible that the longer shaft could force the case halves apart, creating play for the shaft that was shimmed slightly shorter? (Even if both shafts appeared to have proper preload, when studied individually.)

Visually, the bearing bores on the case look like they would move together, since they are so close.

I am wondering if the small amount of compliance between both bearing bores is enough to avoid problems, in conjunction with the shim increments. Is that how the setup works?
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Re: Muncie insights

Post by The Dark Side of Will »

Since preloading a bearing depends on "stretching" the case anyway, stretching the part next to the part a couple 0.001's more probably won't do much... might cock the bearing seat just a smidge, because there's one side that's not pulling as hard as the other three. I think you'd be really hard pressed to tell a difference, even if you got to wear some bearings out.

For the record, the F40 ALSO has all shafts running in tapered roller pairs.

The 282, and I *think* the F23, have some kind of sealed bearings at the outer locations which can take the thrust loads from the gear tooth helix angles. They need only straight rollers at the inner ends. The diffs are the only tapered roller pairs in those two boxes.
pmbrunelle
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Re: Muncie insights

Post by pmbrunelle »

Yeah, I figure that there might be some cocking going on.

Back in the pre-FEA days, probably it would have been pretty simple to characterize case stretch by applying forces and measuring movements with dial indicators.

Then, the distance preload spec could be translated into a force preload range, which could be compared with the bearings' axial load capacities.
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Re: Muncie insights

Post by The Dark Side of Will »

Also need to look at it over temperature, because the aluminum case expands more than the steel shafts and cast iron diff carrier. A higher operating temp would want a higher cold pre-load in order to achieve desired operating pre-load.
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