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What is a Powerglide
transmission?
When was the TH350 transmission first
offered?
When was the TH400 transmission first
offered?
What were the stock tranny gear ratios for the
Muncies?
What is that whining noise coming from my Muncie
M22?
What is a Powerglide
transmission?
It was the "base" 2-speed automatic tranny on the
small-block Camaros. Many base Camaros were ordered up with the
Powerglide.
It's a good transmission and capable of very respectable performance. The
Powerglide in 'built' form was the preferred drag-race transmission for quite a
few years until the TH350s and TH400s came around.
The Powerglide was available on SS350 (295/300HP)
Camaros, and fairly common though many SS buyers opted for the 3-speed TH350 in
1969 if they wanted an automatic.
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When was the TH350
transmission first offered?
The TH350 wasn't officially offered as an option
(RPO) until 1969, although some 1968 327/275 Camaros did manage to get the
3-speed TH350 as they were part of an internal GM test fleet. The only way to
identify if your 1968 car has an original TH350, would be by a date code.
Surprisingly enough in 1969, when the TH350 did become available, consumers
really must have really liked it as the it outsold the Powerglide 78,849 units
to 66,423. Mostly 6 cylinder and small block cars got the
tranny. It was never
used on the big blocks as it wasn't powerful enough (350 lb-ft of torque, hence
the "350"). The big blocks got the TH400 (400 lb-ft of torque capacity).
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When was the TH400
transmission first offered?
The TH400 first appeared on GM passenger cars in
1965. It was available on all first gen big block
Camaros. Although, it was
also used in some small block applications.
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What were the stock
tranny gear ratios for the Muncies?
They were as follows:
Series Gear Ratios Input Grooves Output
(Ratio) Years 1st 2nd 3rd 4th Spline (Input) Spline
-----------------------------------------------------------------------
M20 (Wide) 63-65 2.56 1.91 1.48 1.00 10 None-7/8" clust pin 27
M20 (Wide) 66-71 2.52 1.88 1.46 1.00 10 2 - 1" cluster pin 27
M21 (Close) 63-71 2.20 1.64 1.28 1.00 10 1 - 1" cluster pin 27
and 7/8" clust pin
M20 (Wide) 71-74 2.52 1.88 1.46 1.00 26 2 - 1" cluster pin 32
M21 (Close) 71-74 2.20 1.64 1.28 1.00 26 1 - 1" cluster pin 32
M22 (Close) 65-69 2.20 1.64 1.28 1.00 10 None-1" cluster pin 27
M22 (Close) 70-74 2.20 1.64 1.28 1.00 26 None-1" cluster pin 32
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What is that whining
noise coming from my Muncie M22?
This noise is normal and has to do with the angle at
which the gears mesh. You'll usually hear in 1st, 2nd, and 3rd gear (but not
4th) after you've accelerated and you then release the gas pedal, letting the
car slow down with the engine force. It almost the same sound as when you're in
reverse. The M22 has a shallower mesh angle which causes the "whine". The
reason for the angle change is that it increases the load carrying capacity of
the gears. The disadvantage is the increased noise. Those who selected the M22
over the M21 decided that they could live with the gear noise for the increased
strength. The reason you don't hear it in 4th gear is that 4th is a direct
output from the input (1:1 ratio), and there are no significant gears
involved.
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