I have an 88 with a Series III SC with an aluminum flywheel in front of a 282 Getrag. I put Redline MTL in it when the motor went in and it had the Getrag, marbles in a can, rattle at idle. I got tired of hearing it and tried the old GM # 12345349 synchromesh in it. It didn't do anything for the rattle but seemed to shift a little better.
I just changed to Redline MT 90 and it made a huge difference. It still makes a little noise at idle but way less than before. It shifts much better also. I am thinking draining 1/2 quart out and adding some Redline Lightweight Shockproof and see what that does.
The heavier oil might be an issue during the winter but mine is not a DD so I won't be driving it when it's cold. Makes me wonder if the 5W30 transmission oil spec was a result of the CAFE standards like the 0W and 5W 30 engine oil requirements.
I just changed to Redline MT 90 and it made a huge difference. It still makes a little noise at idle but way less than before. It shifts much better also. I am thinking draining 1/2 quart out and adding some Redline Lightweight Shockproof and see what that does.
Interesting. The following was posted very recently.
My ´88 Fiero with higher viscosity oil shifts easier than my ´87 Fiero with thin 5W30! Therefore, I would say the transmission oil has only a slight influence on shifting effort.
There are Getrag transmissions which shift easy into 1st gear and others not. Each transmission is different, there´re different tolerances, etc. A transmission with “bad tolerances” can lead to higher friction on some contact surfaces and thus it shifts with more resistance.
FYI: I run 75W90 in order to reduce the axle seal leakage. But of course not only leakage is reduced with higher viscosity oil, it also improves resistance to flank scuffing, pitting and improves bearing lifetime. Therefore, I run 75W90 now.
I thought I might be pushing the limits by having added one or two ounces of STP oil supplement to the 10w-30 dino oil in my Formula's Getrag, but I guess not.
Some people swear that "gear oil" will destroy a Getrag, due to it being so much thicker than what was originally recommended (5w-30).
[This message has been edited by Patrick (edited 11-15-2015).]
Myself I run half synchromesh and half Lucas, as the Lucas will stick to gears and climb up the gears, and that is exactly how the Getrags oils themselves.
I myself have ran a Kia Manual trans with a hole in the bottom for over 800 miles only feeding it a quart of Lucas every week (Big gaping hole) so that stuff does work
The MT-90 is also awesome stuff, but it's main goal is to reduce impact damage. if you pour a dime size amount onto a table or the floor and hit it with a hammer it will actually adhere to it's self and stick to the hammer and not splatter anywhere.
If you are considered about running the 90wt MT-90 redline also has a lighter weight version of the MT-90 called "Shockproof 75w90NS" which is comparable to Motul Gear 300
I think that the moly would be too slippery for the synchros to work right. I asked Dave at Redline about their Shockproof oil and he does not recommend any oil with friction modifiers for synchronized transmissions for that reason.
He suggested adding some 75W140NS, no friction modifiers, if I decide I want to increase the viscosity to try and eliminate the last bit of rattle. I may try that next summer if the summer heat brings the louder rattle back.
Here's what UUC Motorwerks recommends to cure gear rattle in BMW manual transmissions
Make: BMW Models: All BMW models including E46, E39, E36, Z3, and Z4
BMW Transmission Rattle / Gear rattle / Gear lash noise
With most any lightened flywheel, everyone sees the benefits immediately due to the reduction of the rotation weight. However, if there is a downside, it's the possibility of a rattle sound that may be evident at idle/low rpm. Note that this particular effect is only evident at idle with the clutch let out.
For details on what actually causes the sound, click here.
Heavier weight transmission fluid will damp the rattle effect, but may not be suitable for cold climates or high-mileage transmissions. The goal, then, would be to find a fluid that would have the high-temp heavy viscosity to damp the rattle but retain the low-temp thin viscosity and synchro additives to ensure all-condition smooth operation.
After experimenting with different weight transmission lubricants, we have come up with a formula that eliminates the gear rattle in the majority of test cars.
The recipe:
1 quart bottle of Redline 75W140NS Gear Oil. ( click here to order ) The "NS" oils have no friction modifiers, thus does not increase shifting effort. From the Redline information about the gear oil: "a GL-5 which does not contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting."
and...
1 quart bottle of Redline D4 Synthetic ATF. ( click here to order ) "D4 ATF is designed to satisfy the improved low-temperature requirements which will be in the new Dexron IV specification, and the improved shear-stability requirements which will be part of the new Mercon specifications. The balanced frictional characteristics provide smooth and consistent shifts for extended drain intervals. Provides improved shifting in cold weather."
How to use:
Drain the transmission (preferably when warm so as to allow as much of the original fluid to drain). Put in the full bottle of 75W140NS, then fill the remainder with the D4 ATF. Note that the majority of BMW transmissions will not take 2 complete quarts, so you will be left with approximately 1/5th of the bottle of D4.
HOT CLIMATE MIX
If you live in an area that is normally hotter than average (California or any Southern or SouthWestern state) then the ambient temps might make your transmission run hotter. In turn, this lowers the viscosity of the transmission fluid, which lessens it's ability to damp the gearbox rattle. Such being the case, we suggest substituting Redline MT-90 for the D4 ATF. So the mix is 1 bottle 75W140NS and the remainder of 1 bottle of MT-90.
MT-90: "MT-90 Manual Transmission Lubricant; a 75W90 GL-4 gear oil designed for use in manual transmissions and transaxles. Provides excellent protection of gears and synchronizers and its balanced slipperiness provides a perfect coefficient of friction, allowing easier shifting." ( click here to order )
Here's what UUC Motorwerks recommends to cure gear rattle in BMW manual transmissions
Make: BMW Models: All BMW models including E46, E39, E36, Z3, and Z4
BMW Transmission Rattle / Gear rattle / Gear lash noise
With most any lightened flywheel, everyone sees the benefits immediately due to the reduction of the rotation weight. However, if there is a downside, it's the possibility of a rattle sound that may be evident at idle/low rpm. Note that this particular effect is only evident at idle with the clutch let out.
For details on what actually causes the sound, click here.
Heavier weight transmission fluid will damp the rattle effect, but may not be suitable for cold climates or high-mileage transmissions. The goal, then, would be to find a fluid that would have the high-temp heavy viscosity to damp the rattle but retain the low-temp thin viscosity and synchro additives to ensure all-condition smooth operation.
After experimenting with different weight transmission lubricants, we have come up with a formula that eliminates the gear rattle in the majority of test cars.
The recipe:
1 quart bottle of Redline 75W140NS Gear Oil. ( click here to order ) The "NS" oils have no friction modifiers, thus does not increase shifting effort. From the Redline information about the gear oil: "a GL-5 which does not contain the friction modifiers for limited-slip hypoid differentials. This makes the transmission synchronizers come to equal speeds more quickly, allowing faster shifting and much easier low-temperature shifting."
and...
1 quart bottle of Redline D4 Synthetic ATF. ( click here to order ) "D4 ATF is designed to satisfy the improved low-temperature requirements which will be in the new Dexron IV specification, and the improved shear-stability requirements which will be part of the new Mercon specifications. The balanced frictional characteristics provide smooth and consistent shifts for extended drain intervals. Provides improved shifting in cold weather."
How to use:
Drain the transmission (preferably when warm so as to allow as much of the original fluid to drain). Put in the full bottle of 75W140NS, then fill the remainder with the D4 ATF. Note that the majority of BMW transmissions will not take 2 complete quarts, so you will be left with approximately 1/5th of the bottle of D4.
HOT CLIMATE MIX
If you live in an area that is normally hotter than average (California or any Southern or SouthWestern state) then the ambient temps might make your transmission run hotter. In turn, this lowers the viscosity of the transmission fluid, which lessens it's ability to damp the gearbox rattle. Such being the case, we suggest substituting Redline MT-90 for the D4 ATF. So the mix is 1 bottle 75W140NS and the remainder of 1 bottle of MT-90.
MT-90: "MT-90 Manual Transmission Lubricant; a 75W90 GL-4 gear oil designed for use in manual transmissions and transaxles. Provides excellent protection of gears and synchronizers and its balanced slipperiness provides a perfect coefficient of friction, allowing easier shifting." ( click here to order )
At some point I plan to try either MT90 or 75W140NS / D4 ATF.
I am currently running Redline MTL.
"MTL is a low 75W, almost a 70W, at very low temperatures and a high 80W, nearly an 85W, at elevated temperatures, providing adequate viscosity to prevent wear and deaden gear noise. MT-90 is a thicker 75W90 version of MTL. The shear stability and oxidation stability of these products are excellent, thus the physical characteristics of Red Line MTL and MT-90 will change little with use. Red Line MTL is classified as a 75W/80W gear lubricant satisfying the API Service requirements of GL-3 and GL-4. MTL also satisfies motor oil viscosities SAE 5W/10W/30, and the viscosity requirements for ATFs. MT-90 is a 75W90 GL-4 and also satisfies motor oil viscosities SAE 10W/15W/40. The additive chemistry used is non-corrosive, so even though they will provide GL-4 performance, they will not corrode synchros or bushings. Because of its low corrosivity, Red Line MTL and MT-90 could also be used in transmissions requiring GL-1 or GL-3 lubricants. Seal compatibility is designed to be similar to petroleum-based lubricants." http://www.redlineoil.com/c...90%20Tech%20Info.pdf
I have an 88 with a Series III SC with an aluminum flywheel in front of a 282 Getrag. I put Redline MTL in it when the motor went in and it had the Getrag, marbles in a can, rattle at idle. I got tired of hearing it and tried the old GM # 12345349 synchromesh in it. It didn't do anything for the rattle but seemed to shift a little better.
I just changed to Redline MT 90 and it made a huge difference. It still makes a little noise at idle but way less than before. It shifts much better also. I am thinking draining 1/2 quart out and adding some Redline Lightweight Shockproof and see what that does.
The heavier oil might be an issue during the winter but mine is not a DD so I won't be driving it when it's cold. Makes me wonder if the 5W30 transmission oil spec was a result of the CAFE standards like the 0W and 5W 30 engine oil requirements.
I replaced one quart of Redline MT90 with a quart of 75W140NS today and drove about 30 miles to see what difference it would make.
The temperature was about 70 degrees, the shifting is pretty much the same as with all MT90, which is a little better than it was with the MTL, and the rattle is quiet.
I hope that summer temps don't bring the rattle back. If it does I'll try adding another quart of the 75W140NS.
Here's what Redline says about using 75W140NS in transmissions.
Contains extreme pressure additives like our 75W140 GL-5 oil, but lacks friction modifiers to balance slipperiness
Popular for historic and vintage transmissions, like Mid-1930s to early-1950s synchro-equipped gearboxes in cars and trucks Helps with noisy or rough shifting in troubled A-833 Dodge/Plymouth 4-speed transmissions from 1964 to 1969
Option for noisy transmissions when mixed with 75W90NS or MT-90 to bring viscosity level up
I wonder if there would be a problem replacing 1 quart of MTL with 75W140NS, I already have MTL in it, maybe I can skip the MT90 step?
I elected to just drain the MTL because I was going with straight MT90. The vis numbers of the oils at 100 degrees centigrade are MTL - 10.4, MT90 - 15.6 and 75W140NS - 26.9. I don't have a clue what the numbers are after mixing but there are many discussions about different Redline oil cocktails for other Getrag transmissions that also have gear rattle at idle. Mine still has a very slight rattle, I may add another quart of 75W140NS when summer gets here.
You could always add more 75W140 to the MTL if 1 quart doesn't cut the rattle down as much as you want.
I've been interested in this thread from the very start as I have a Formula with the infamous "Getrag rattle".
However, I've now also got added interest in this topic as I'm currently on the fence making a decision on whether to buy an earlier model Mitsubishi 3000GT VR4... which came from the factory with 5-spd Getrags... and which often suffer from "tired" synchros.
I don't wish to send this thread off in a totally different direction (let's keep it Fiero oriented), but if anyone has any comments or advice on what oil might be helpful to use in the 3000GT Getrag tranny, please send me a PM. Thanks.
[EDIT] I decided against buying a 3000GT VR4 (bought a JDM Subie instead), so I no longer require insight on the Mitsubishi's Getrag tranny.
[This message has been edited by Patrick (edited 06-09-2018).]
In really hot temps my Getrag transmission still had a slight rattle at idle with the Redline mix. I put straight 75w140 NS oil in and it is better. It also shifts a little better and is easier to shift from neutral to first when stopped.
Straight 75w140 NS may be hard to shift in really cold temps but I don't drive it in the winter anyway.
Coincidentally, I was researching BG Syncroshift ii against the GM Syncromesh. It didn't get much traffic on the thread I started.
The BG is 75w-80, which I realize isn't as thick as what you are running. But . . . gear oil viscosity is measured differently than motor oil. Generalizing, the 75w-80 gear oil is very close to 10w-30 or 10w-40 motor oil. Point here, if you are running 75w-140, your cold temp viscosity (the 75w) might not be that far off. The thicker hot temp viscosity would explain why you were able to silence the rattle.
API Service Class GL 5+ SAE Viscosity Grade (Gear Oil) 75W140 Vis @ 100°C, cSt 26.9 Vis @ 40°C, cSt 179 Viscosity Index 188 Pour Point, °C -45 Pour Point, °F -49 Brookfield Viscosity, Poise 1200 @-40°C
Contains extreme pressure additives like our 75W140 GL-5 oil, but lacks friction modifiers to balance slipperiness
Popular for historic and vintage transmissions, like Mid-1930s to early-1950s synchro-equipped gearboxes in cars and trucks
Helps with noisy or rough shifting in troubled A-833 Dodge/Plymouth 4-speed transmissions from 1964 to 1969
Option for noisy transmissions when mixed with 75W90NS or MT-90 to bring viscosity level up
Also used in clutch-type limited slip differentials in racing for maximum lock up-some users add Limited Slip Friction Modifier in small doses to customize slippage
Recommended for API GL-5, GL-6, MT-1, MIL-L-2105E, and SAE J2360
Some people swear that "gear oil" will destroy a Getrag, due to it being so much thicker than what was originally recommended (5w-30).
I am one that's thoroughly convinced. When I had the clutch replaced in my first 85GT, the garage refilled the transmission with 80 w 90 hypoid gear oil. I got 80 miles out of the transmission before it broke, and all of that except 9 miles was interstate driving.
I am one that's thoroughly convinced. When I had the clutch replaced in my first 85GT, the garage refilled the transmission with 80 w 90 hypoid gear oil. I got 80 miles out of the transmission before it broke, and all of that except 9 miles was interstate driving.
I'm not sure what viscosity half MTL and half 140 ends up, but its been good for around 3k miles so far.
API Service Class GL 5+ SAE Viscosity Grade (Gear Oil) 75W140 Vis @ 100°C, cSt 26.9 Vis @ 40°C, cSt 179 Viscosity Index 188 Pour Point, °C -45 Pour Point, °F -49 Brookfield Viscosity, Poise 1200 @-40°C
Contains extreme pressure additives like our 75W140 GL-5 oil, but lacks friction modifiers to balance slipperiness
Popular for historic and vintage transmissions, like Mid-1930s to early-1950s synchro-equipped gearboxes in cars and trucks
Helps with noisy or rough shifting in troubled A-833 Dodge/Plymouth 4-speed transmissions from 1964 to 1969
Option for noisy transmissions when mixed with 75W90NS or MT-90 to bring viscosity level up
Also used in clutch-type limited slip differentials in racing for maximum lock up-some users add Limited Slip Friction Modifier in small doses to customize slippage
Recommended for API GL-5, GL-6, MT-1, MIL-L-2105E, and SAE J2360
This is good info, and it would indicate the viscosity is further off from others (such as Syncromesh) than I thought. The Pennzoil Syncromesh has a 100C viscosity of only 9.08 cSt and a 40C viscosity of 41.6.
When you first hear the Getrag rattle its a little unnerving. The Getrag rattle is the sound the Getrag transmissions (particularly 5 speed’s like those found in E30’s, BMW’s and GM’s) makes when it is in Neutral and the clutch pedal is not engaged.
The sound completely goes away when either the clutch pedal is engaged or the car is in gear.
Some would describe the sound like a bag of marbles, gear chatter, or similar metal rattling.
The sound is not a fault within the transmission, rather what you are hearing is the unengaged gears vibrating against their neighbors.
If you have ever heard a large 18 wheeler idle in neutral you would have likely heard a loud metal rattling sound as well. Again its not because the truck is broken, its because of the play in the gears when not engaged. The sound is louder in an 18 wheeler because the gears are bigger.
As the transmission accumulates miles the sound may get louder as the gears and bearing clearances inside become ever so slightly larger. It is not indicative of the transmission failing.
Never the less its annoying and sometimes embarrassing.
The noise can be significantly effected depending on the transmission oil you use. The thicker the oil, the harder the gears and bearings have to work to bounce around.
The solution is to mix one part 75w80 (or similar) and one part heavy weight oil like 75w-140 or 85w-140."
