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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The Dark Side of Will
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Muncie insights

Post by The Dark Side of Will »

I assembled a hybrid Muncie yesterday and today.

I'm using the 1st (and second) gear and case from a V6 box with 4th (and 3rd) and FD from economy 4 cylinder trans. I also installed an EP LSD. This is going to a customer doing a 383 swap.

In no particular order:

The V6 and I4 second gears have the same ratio, but different tooth counts: 20:39 (V6) vs 22:43 (I4).

The Muncie is refreshingly simple compared to the Getrag. Trust the Germans to complicate things. The Getrag has 3 shift rails for 5 forward gears. The Muncie has 1 shift rail for 4 forward gears. The shifted gears in the Getrag ride on needle bearings. The shifted gears in the Muncie ride on plain bearings. The lubrication for these bearings is handled in a very complicated way involving small fabbed sheet metal pieces in the Getrag. It's very simple in the Muncie, involving a couple of casting features and a couple of simple machining steps during manufacture.

The short Muncie 1st and the tall 1st both have the same number of teeth on the output gear. Don't confuse them.

The early transmission has separate 3rd & 4th output gears that spline on to separate locations on the output shaft. The later V6 transmission has 3rd & 4th outputs as a single cluster that splines to one location on the shaft. The Getrag uses a heat-shrink press fit of the 3-4 cluster on the output shaft. The V6 box also has a screw in retainer on the outer end of the output shaft. This has LEFT hand threads. The older transmission does not have this. All of these features make it necessary to keep 3rd & 4th with the output shafts they were originally on. These gears can't be swapped from I4 to V6 transmission.

The input shaft outer bearing is a slip fit, not a press.

All three shafts use tapered roller bearings. The toolset for selecting the shims for these bearings can be had on ebay for $20 or so (I'll have the tool number tomorrow... don't remember right now and it's still at the shop).

The Muncie uses the same diff carrier bearings as the Getrag. The diff bearing shim part of the Muncie tool kit can also be used in the Getrag.

There are Chrysler transmissions that use the same bearings as the Muncie. I'm tracking down the Chrysler P/N's for the shims.

I've got some other things like tooth loading charts and such, but I'll put those up later.
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Post by MNFatz »

Scroll about 1/2 way down the page. There's a pic of the shim selector and the tool number there.

http://realfierotech.com/phpBB/viewtopi ... c&start=40
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Post by The Dark Side of Will »

Yup. J-26935. I got mine cheap. That is in fact the thread that planted the idea in my head.

There's a toolset for the Getrag that lists for over $700, but this will do the Getrag as well.
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Post by MNFatz »

I wished I would have known about the gearset swap.

I swapped in 84 econo internals in an 85 case. 1st gear is worthless and even 2nd could be a little taller.

I'm not sure what to think about the 3/4 hop. I'm not sure that 4th gear is the right choice for a good 1/4 mile. Outstanding for highway cruising though.

I've got an extra isuzu laying around. How truly crappy are they? I could crack mine open and take some pics.
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Post by crzyone »

So in your opinion which transmission is built stronger? The V-6 muncie or the getrag?
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Post by The Dark Side of Will »

I think it's a toss-up.

If you wanted to split hairs, you might be able to call the Muncie better, because the 3.31 first has 10% lower specific tooth load (lbs of tooth load per inch of tooth width per ftlb of input torque). The Getrag and the 4 cylinder Muncie both have about the same specific tooth load in 1st.

I really can't make any judgements about the cases. That the V6 Muncie case is stronger than the 4 cylinder case is obvious. However, I think the relative strengths of the Getrag & V6 Muncie cases is pretty much impossible to tell by visual inspection.

I've never heard of someone breaking a couple of one, then switching to the other and not having problems.
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Post by p8ntman442 »

FWIW the izuzu five speed uses the same 3 shift rails to shift 5 gears and it oils the tranny with a bunch of plastic rails that become brittle after a while.

My experiance with getrag 5 spds is that the output shafts are not all the same within the same year depending on application. The muncie is deffinatly a easy tranny to dig into and put back together, then its the getrag, and the izuzu is the biggest pita.
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Post by The Dark Side of Will »

Parts:

Input shaft seal: 3732S
Axle Seals: 3543 (same as Getrag)
Shift shaft seal: 3667

Input shaft inner bearing: SET4 (Timken); A4 (general industry)
Output shaft inner bearing: SET5 (Timken); A5 (industry)
BOTH outer bearings: 15101 (Cone) & 15245 (Cup)
Diff carrier bearings: SET11 (Timken); A18 (industry) (Same as Getrag)

Information from:
http://www.timken.com/industries/automo ... talog.aspx

The input shaft shims have been discon by GM.
Several Chrysler transmissions use them, so they should be available from Chrysler for some time now.

Code: Select all

Input Inner Bearing (SET4) Shims
Chrysler P/N's
P/N          Thickness
04202751     0.62mm
04202301     0.66
04202302     0.70
04202303     0.74
04202304     0.78
04202305     0.82
04202306     0.86
04202307     0.90
04202308     0.94
04202309     0.98
04202310     1.02
04202311     1.06
04202312     1.10
04202313     1.14
04202314     1.18
04202315     1.22
04202316     1.26
04202317     1.30
04202318     1.34
04202319     1.38
04202320     1.42
04202321     1.46
04202322     1.50
04202323     1.54
04202324     1.58
04202325     1.62
04202326     1.66
04419650     1.70
04202753     1.74
04202754     1.78


Diff (SET11) & Output Inner Bearing (SET5) Shims
Shim dimensions:2.421 OD     2.165 ID
Chrysler P/N's
P/N          Thickness
04883546AA   0.42
04883545AA   0.46
05222345     0.50
05222346     0.54
05222347     0.58
05222348     0.62
05222349     0.66
05222350     0.70
05222351     0.74
05222352     0.78
05222353     0.82
05222354     0.86
05222355     0.90
05222356     0.94
05222357     0.98
05222358     1.02
05222359     1.06
05222360     1.10
05222361     1.14
05222362     1.18
05222363     1.22
05222364     1.26
05222365     1.30
05222366     1.34
05222367     1.38
05222368     1.42
05222369     1.46
05222370     1.50
05222371     1.54
05222372     1.58
The diff shim dimensions are 55mm (2.165) ID, 61.5mm (2.421) OD.
These shims are useable on BOTH the diff AND the output shaft of the Muncie.
Last edited by The Dark Side of Will on Wed Jun 21, 2006 1:57 pm, edited 1 time in total.
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Post by The Dark Side of Will »

p8ntman442 wrote:FWIW the izuzu five speed uses the same 3 shift rails to shift 5 gears and it oils the tranny with a bunch of plastic rails that become brittle after a while.

My experiance with getrag 5 spds is that the output shafts are not all the same within the same year depending on application. The muncie is deffinatly a easy tranny to dig into and put back together, then its the getrag, and the izuzu is the biggest pita.

I haven't been inside an Isuzu, but I thought from the relative thicknesses of the overhaul instructions that the Isuzu would have been much easier than the Getrag.

The Getrag output shaft differences only vary by final drive ratio... which varies by application. The 3.94 setup has a thrust washer and a roller 1st gear bearing. The 3.61 has a needle 1st gear bearing and a needle thrust bearing.
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Post by MNFatz »

And heres what it all looks like. The kits come with all the bearings, races, input shaft seal and axle seals. The part number is in the lower right hand corner of the pic. This one came from www.drivetrain.com Good vendor, but old fashioned. Submit your order and call them to make sure they got it.
Image

The last time I checked synchros were still expensive. In the 84 I tore apart one of the synchros was obviously bad, the other one looked like new. It's a shame not to replace these.

You probably should replace the fork bushings as well, but I didn't bother.
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Post by The Dark Side of Will »

The blocker rings are ~$100 each.
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Post by The Dark Side of Will »

I fixed/improved the Chrysler shim P/N table

Here are the GM P/N's:

Code: Select all

GM P/N's
4.376 - Shim, Transmission Input Gear
463077     1.50mm
463078     1.60
463069     1.70
463070     1.80
463071     1.90
463072     2.00
463073     2.10
463074     2.20
463075     2.30
463076     2.40
465401     2.50
465402     2.60
463079     2.70
463080     2.80
463081     2.90
463082     3.00

4.412 - Shield-Shim, Trans Output Gear
463049     1.50mm
463050     1.60
463041     1.70
463042     1.80
463043     1.90
463044     2.00
463045     2.10
463046     2.20
463047     2.30
463048     2.40
463053     2,50
463054     2.60
463051     2.70
463052     2.80
I couldn't find a listing for differential bearing shims, so presumably the GM shims work in both positions as well, although the ones I pulled out of this transmission were different.

Waitaminnit... I wonder if I have to look in the axle group, as opposed to the transmission group for the diff bearing shims... Freakin' GM... WTF?

Anyway, I've been told the GM shims are discon, but I'll submit this list to the local dealershp and find out for myself.
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Post by The Dark Side of Will »

I forgot to put the oil shield retainer on top of the output shaft shim gauge when I put the setup together to measure. I'll just subtract the thickness of that part from the output shaft measurement.

On the Input shaft, I measured 0.107 clearance on the tool.
On the Output shaft, I measured 0.112 clearance - 0.036 for the retainer gives 0.076 gap.
On the diff I measured 0.068 clearance.

The manual says:

"Determine the largest shim that can be placed into the gap and drawn through without binding. Use the next shim size smaller for the output shaft and differential. On the input shaft, use two sizes smaller. If end play occurs, use the next larger shim sizes."

It does NOT give acceptable end play specifications, though.

Anyway, the smallest GM shim that would go through the input shaft gap of 0.107 would be 2.70mm, which means that according to the manual, I should use the 2.50mm shim.

The smallest GM shim that would fit in the output shaft gap of 0.076 would be 1.90mm, so I should use the 1.80mm shim.

On the diff, the 0.068 gap would fit a 1.70mm shim and thus require 1.60mm shim, which is very close to the bottom of the GM range.

The euivalent Chrysler thicknesses are:
Input: 2.50 - 2 x 1.26
Output: 1.80 - 2 x 0.90
Diff: 1.60 - 1.58 OR 2 x 0.82

However, further consideration reveals that GM's shim specs allow 0.009-0.011 end play on the input shaft and 0.005-0.007 on the output shaft and diff.
The Getrag uses the same bearings and is assmbled with 0.003-0.004 *preload* rather than end play.

I'm inclined to go down to zero end play on the Muncie, despite GM's recommendations. The differential coefficients of expansion of the aluminum case and steel shafts will increase the end play as the transmission warms up, and since this trans will be subject to SIGNIFICANTLY more than its rated throughput, I'd like to have the clearances as tight as reasonable.
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Post by The Dark Side of Will »

I hate being run around in circles by someone else's stupidity.

Common Sense and Occam's Razor both inidicate that the collapsed height of the telescoping gauges in the shim selection toolset should be the same as the length of the spacers that hold the case halves apart. This would make the gaps in the telescoping gauges directly comparable to the gaps that would be behind the races.

However, the F#@%ing Dumb@$$ who designed this tool apparently made little of either common sense OR Occam's Razor and made the collapsed height of the gauges .010 SHORTER than the length of the spacers.

DAMMMIT

So what I thought was excessive end play is actually acceptable preload... and I've wasted several days figuring that out because of the fucking moron who thought he knew better than to make things as simple as they obviously & fucking well ought to be.

Anyway... shims to be ordered momentarily.
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Post by The Dark Side of Will »

Revising the shim specs:
Input: 2x1.26mm (04202316)
Output: 2x0.90mm (05222355)
Diff: 0.82 + 0.78 (05222353, 05222352).
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Post by Pyrthian »

The Dark Side of Will wrote:However, the F#@%ing Dumb@$$ who designed this tool apparently made little of either common sense OR Occam's Razor and made the collapsed height of the gauges .010 SHORTER than the length of the spacers.
could that be for the space of the sealant for when they get assembled?
no, I guess not - then it would have to be longer, not shorter...nm
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Post by The Dark Side of Will »

The O-ring that seals the TOB support/Input shaft seal retainer/Input shaft bearing retainer to the case appears to be an 034.
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Post by The Dark Side of Will »

The Dark Side of Will wrote: The diff shim dimensions are 55mm (2.165) ID, 61.5mm (2.421) OD.
These shims are useable on BOTH the diff AND the output shaft of the Muncie.
Looking up this thread for someone reminded me to fixt this...

This info is NOT correct. The diff shims are NOT useable in the output shaft shim location. The OD is slightly wrong. I ended up having to (precision) grind down the old output shim to work with the other output shaft.
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Re: Muncie insights

Post by The Dark Side of Will »

Since I never posted the full tool info here:
The Dark Side of Will wrote:The stand-offs are:

4.5088
4.5109
4.5088
4.5082
4.5079
4.5084
4.5080
AVG: 4.5087

26935-2 (Input shaft)
4.3750 + 0.3494 - 0.2466 = 4.4778
Difference: 0.0309 (!! WTF?!?)

26935-4 (Output shaft)
4.3775 + 0.3757 - 0.2530 = 4.5002
Difference: 0.0085

26935-3 (Differential)
4.3814 + 0.3778 - 0.2598 = 4.4994
Difference: 0.0093

Positive Difference -> Tool gap wider than actual gap.
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Re: Muncie insights

Post by Emc209i »

Ten years after the original post, and thirty years after the transmission was first used! 8)
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