MD9 3-SPEED AUTO 125THC ONLY AUTO USED MG2 5-SPEED MANUAL MUNCIE 3.61 RATIO V6 ONLY MT2 5-SPEED MANUAL ISUZU 3.35 RATIO L4 ONLY MY8 4-SPEED MANUAL MUNCIE 3.32 RATIO 1984 L4 ONLY M17 4-SPEED MANUAL MUNCIE 3.65 RATIO V6 ONLY M19 4-SPEED MANUAL MUNCIE 4.10 RATIO 1984 L4 ONLY
Note: MG2 is the Getrag-designed Muncie built transaxle
Note: the V6 Muncie is stronger than the L4.
Final
1st 2nd 3rd 4th 5th Drive RPO
1984 L4 3.53 1.95 1.24 0.73 3.32 MY8
1984 L4 3.53 1.95 1.24 0.73 4.10 M19
1985 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1985 V6 3.31 1.95 1.24 0.81 3.65 M17
1986 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1986 V6 3.31 1.95 1.24 0.81 3.65 M17
1987 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1987 V6 3.50 2.05 1.38 0.94 0.72 3.61 MG2
1988 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1988 V6 3.50 2.05 1.38 0.94 0.72 3.61 MG2
1st 2nd 3rd
MD9 2.84 1.60 1.00
Final
Drive Code RPO
1984 3.18 PF MD9
1985 3.06 CD MD9
1985 3.18 PF MD9
1986 3.06 6CD MD9
1986 3.18 6PF MD9
1987 3.33 7CPC MD9
1987 2.84 7PSC MD9
1988 3.33 8CPC MD9
1988 2.84 8PSC MD9
From PENN-JERSEY FIERO CLUB NEWSLETTER No. 9, corrections and additions from Scott Backer
Each of these transaxles are used on many different GM front wheel drive cars as well as on the Fiero. There are a range of different final drive axle ratios available depending on the car and the year etc. but they are all basically the same internally and have the same bell housing bolt pattern.
This means that any of them can bolt up to either the 2.5 litre 4 cyl. engine or the 2.8 litre 6 cyl. or for that matter the Quad-4 or the 3.8 litre monster-motor. The difference is in their capacity for torque and in the arrangements of the external shifting mechanism which is a bit unique on the Fiero.
As for the torque capacity - the Isuzu will fit the V6 cars but is said to not be heavily enough built to take the torque - so this is not a good swap. Zolt in Toronto had an Isuzu in a V6 car and it only lasted a year or so before melting down on a fast trip down a freeway (ouch).
The [V6's] 4 speed Muncie is very heavily built and can be used with any engine including a V8 (within reason) and the 5 speed Getrag is also a heavy duty unit.
From: Peter Frise (edited with corrections from Scott Backer)
All manual 1984 cars had the Muncie 4-speed transaxle. All 4-cylinder cars made in 1985 and later had the Isuzu 5-speed. 1985-1986 V6 models used the Muncie 4-speed. Sometime in late '86, Pontiac introduced the Muncie/Getrag 5-speed in the V6 which was used for the rest of production. When did they change? See below.
From: Sketch
Based on research I did some time ago, the earliest VIN with a 5-speed has the last 6 digits as 277411. At this time I would say that any lower # is a 4-speed until we can verify a lower build #. Since 83,974 86's were built, the 5-speeds started appearing somewhere around the 77,411 production time. This is only a "lead", be sure to verify mechanicaly.
From: Paul Vargyas
If you can see the trans U can tell if it's a 4-speed or 5-speed. The 5-speed Getrag has the backup light switch almost directly under the shifting linkages at the transaxle. It also has a little dipstick on the aft side of the transaxle just above the left (drivers side) inboard CV joint.
From: Lee Brown
The axle ratio is the "differential" ratio. In the transaxle the differential and transmission are combined in one unit (in "conventional" rear drive, the tranny is up front connected to the engine and a drive shaft then connects to the differential [rear end]).
The axle ratio is the ratio of the input to the output. For example 3.42:1 means 3.42 turns of the output of the transmission for one turn of the axle (wheels).
The transmission might have ratios (way oversimplified) of 1st gear: 3:1; 2nd gear 2:1; 3rd gear 1:1. Overdrive might be 0.95:1 (or 1:1.05).
So, in first gear (using my numbers):
Engine turns 3,000 (RPM)
Trans output is (3000/3:1) 1,000 RPM
Axle ratio is (say) 3.5:1
therefore wheels turn at 286 RPM
(now calculate the circumference of the wheel, allow for slippage of clutch,
tires/road, etc., and you'll get ft/minute and convert to MPH).
This explains why at the same RPM (engine speed) you are traveling at different speeds in different gears (even though the axle ratio stays the same). This also explains why with the same engine and transmission, different axle ratios produce different speeds (and different pulling capability and different MPGs).
From: Ken
"My car grinds when going into first and reverse. My dealer says this is normal. Is it?"
Your dealer's right. Sorry. It's pretty easy to understand if you can see the inside of a manual trans, but kind of hard to explain without it. But I'll try. :-)
First Gear problem:Basically the synchronizers in your trans are little clutches. When the clutch (engine clutch, not synchro clutch) is disengaged, the clutch disk stops spinning. When the car is moving, the output side of the trans is turning (because it's attached to the wheels) but the input side is stopped (because the clutch is dis-engaged). The synchro has to speed up the input side to match the output side and this may be difficult since first is a pretty low gear (input side turns a lot for 1 turn of output side), so there is a mechanical disadvantage when trying to overcome things like friction, the inertia of all the trans parts, and the inertia of the clutch disk. Similarly, if the car is stopped but you just disengaged the clutch, it may be hard to shift into 1st because the shychro is trying to slow down everything that's still spinning. Other gears engage easier because they have less of a mechanical dis-advantage for spinning up (or slowing down) the input side.
Reverse Gear Problem:
Reverse is not synchronized. When you shift into reverse, you are physically engaging two straight cut gears. They will grind if either one of them is moving -- output (because the car is moving) or input (because you just disengaged the clutch and it hasn't spun to a stop yet). If you sit still, shift the car into neutral, disengage the clutch, and wait long enough, it will shift into reverse without grinding. What you're doing when you shift into 3rd then R, is stopping the input shaft. This is because you're matching the input shaft speed to the output shaft speed (which is zero if the car's not rolling). Once they're both stopped -- no grinds.
From: Doug Chase
There are two fill plugs. One is the speedometer fitting. There is a "H" and a "L" indicator on the bottom of the fitting. The second is a fill plug just behind the left (drivers side) axle on the side of the trans. There should be a plastic washer under it that says, "USE WITH 5W-30 FLUID ONLY".
From: Scott Backer
As to draining the transaxle, there is a drain plug in the transaxle approximately between the axles on the very bottom. Drain all the fluid and replace the plug being careful not to tighten it too much (the case is aluminum). The fill hole is on the drivers side of the case slightly aft and above the axles. Use a rubber tube and funnel to replace the oil. Check the transaxle dipstick so as not to over fill. The book lists oil capacity as 1.9L (4.0qts). The problem is that not all of the oil will drain out. So keep an eye on the dipstick when replacing the oil (SAE 5W-30 standard engine oil is recommended).
Be sure to also change the oil filter and clean around the drain plug before you reinstall it. Dirt does not help the plug seal to the oil pan...
From: Lee Brown
"I have a Chilton and Haynes manuals (no Helms). Neither talks about drive shaft removal from the transmission. How much of this must come off? Outer CV joint only, outer and inner CV joints both, or what? Are any special tools required to remove CV joints? I probably want to check these out anyway."
From: Sketch