# which oil is recommended in a muncie 4 speed



## Mr.409 (Apr 22, 2017)

Hello
I just got my muncie out
Can someone tell me which oil is recommended in a muncie 4 speed
Thanks you for info
Carsten


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## PontiacJim (Dec 29, 2012)

Mr.409 said:


> Hello
> I just got my muncie out
> Can someone tell me which oil is recommended in a muncie 4 speed
> Thanks you for info
> Carsten


So you are still working on your car without a Factory Service Manual which will tell you things like this?

My '68 manual says 2 1/2 pints. Lubricant level should be approximately level with bottom of filler plug hole. Use SAE 90 multi-purpose gear lubricant.


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## Mr.409 (Apr 22, 2017)

PontiacJim said:


> So you are still working on your car without a Factory Service Manual which will tell you things like this?
> 
> My '68 manual says 2 1/2 pints. Lubricant level should be approximately level with bottom of filler plug hole. Use SAE 90 multi-purpose gear lubricant.


Thank you for info


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## cij911 (Oct 25, 2017)

Mr.409 said:


> Thank you for info


GL4....not synthetic


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## devildawg (Apr 27, 2012)

I concur with cij911
I would recommend Brad Penn grade 1 'classic' multi purpose GL-4 SAE 80w-90 gear oil. It's made specifically for old Muncie and Borg-Warner transmissions that require mineral base oils. This way your sure your getting a mineral base oil and NOT synthetic.
Ive been running this in my Muncie M-20 since putting it in the vehicle and after doing extensive research on the subject. The chassis shop manual lubrication section for synchro mesh transmissions specify's SAE 80w multi purpose gear lube where available or 90w that meets the specification MIL-L-2105B. ( in other words GL-4 ) . GL = gear load . The transmission rebuild chapter says fill with SAE 90w. Bottom line is you want a mineral base lube. There are so many products out there it's difficult to determine whats synthetic and whats mineral base so thats why I recommend the Brad Penn.


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## geeteeohguy (Feb 2, 2008)

Agree with these gents. Any good non-synthetic 75w/90 gear oil. The synthetic stuff tends to be hard on the synchronizers, due to it's being too slippery for the parts to 'grab' and slow down the gears.


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## cij911 (Oct 25, 2017)

geeteeohguy said:


> Agree with these gents. Any good non-synthetic 75w/90 gear oil. The synthetic stuff tends to be hard on the synchronizers, due to it's being too slippery for the parts to 'grab' and slow down the gears.


I believe it has more to do with the type of metal (but this is debatable).

Here is a great video from one of the Muncie gurus (Paul) :


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## PontiacJim (Dec 29, 2012)

Ok, watched the video. Kind of skewed in his testing as I don't care how the oil pours when cold, I want to know it won't turn to water when it is hot inside the transmission and clings to the gears - kinda useless test. And gear oil whipping around in the transmission causes loss of power? Hmmm, must have been why I got beat by that Rambler with the 401CI and blower on top.

How did we ever get by in the "old days" by simply going to the parts store and picking up a bottle of 80W-90 gear lube and never questioned its molecular make-up or friction modifiers? The same stuff you put in the trans, you used in the rear end and then if you had posi, used an additive.

From my understandings, "our old" gear oil was a GL3.

So what in the hell is GL4, let alone GL5? I did a little research, so this is my opinion. The GL5 is definitely NOT what you want in your Muncie or any other "old car" manual transmission, period. It is for newer vehicles designed for such lubricants. The use of a GL-5 lubricant in a synchromesh transmission with brass synchro's will "shorten the synchronizer life by one half".

Next is the GL4. GL4 fluids may or may not be right for the older transmissions. It all depends on what additives have been introduced into the formula - with each manufacturer/supplier having their own unique formula.

The key is that you want to steer away for the letters "EP" or "XEP." EP= Extreme Pressure additives prevent seizure conditions caused by direct metal-to-metal contact between the parts under high loads. These additives can be: Chlorinated paraffins; Sulphurized fats; Esters; Zinc dialkyldithiophosphate (ZDDP); and Molybdenum disulfide.

Why steer away? Some which contain phosphorous/sulfurous compounds (but not all depending on the EP compound and how much is used) are corrosive to yellow metals such as the copper and/or brass used in bushings and synchronizers on the older manual transmissions.

However, most all GL4 gear oils have some form of EP compounds, so you can't really get by without them. You just want to know what the EP used is and less of it is better. 

In reading online, it seems the GL4 gear oils are going the way of the GL3 that we used to use - obsoleted or more difficult to get as the GL5 and even GL6 becomes the gear oil of choice for those cars still even using a manual gear box anymore.

There are a number of choices to include synthetics that are claimed to be used with the older (Muncie) transmissions and ARE COMPATIBLE with the brass synchro rings and soft metal bushings. Looking around for recommendations I found these"

*CRC Sta-Lube* produces an SAE 85W90 GL-4 gear oil (SL24229) which is perfectly suited to all Muncie, Super T-10, and most T-10 4-speeds. Though originally most Muncie, Super T-10, and T-10 units came from the factory with 75W90 conventional gear lube, it is becoming very hard to find 75W90 conventional in the modern era – 80W90 and 85W90 are more commonly found and both can be safely used as a 75W90 replacement. Sta-Lube SL24229 will protect all the components in these classic 4-speeds and this includes their synchronizers. And it works very well in original Muncie, Super T-10, or T-10 units where the seals have never been replaced. And this is especially important since synthetic gear oil tends to leak out of older transmissions at a much quicker rate than conventional gear oil. https://www.crcindustries.com/products/api-gl-4-multi-purpose-gear-oil-85w90-32-fl-oz-SL24229.html 

*Amsoil* offers a GL4 Synthetic Manual Transmission & Transaxle Gear Lube that includes use with brass synchro's and for older transmissions (Muncie, T-10, Top loader, etc.) It is formulated with seal conditioners to reduce leaks. https://www.amsoil.com/shop/by-prod...-transmission-and-transaxle-gear-lube-75w-90/. 

*Red Line* offers their MT-90 75W90 GL-4 Gear Oil synthetic gear oil for older transmissions. Recommended for GL-1, GL-3 and GL-4 applications and safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage. https://www.redlineoil.com/mt-90-75w90-gl-4-gear-oil

*Red Line* also offers the same mix in a slightly lighter oil viscosity with MT-85 75W85 GL-4 Gear Oil. https://www.redlineoil.com/mt-85-75w85-gl-4-gear-oil

*Red Line* also offers this mix, MTL® 75W80 GL-4 Gear Oil. https://www.redlineoil.com/mtl-75w80-gl-4-gear-oil

There may be other options and brands as I did not try to rifle through all the blogs to see who is using what, but these above seemed to pop up more often in the older car categories. This simply gives you an idea of what to look for and options that can be used in our older manual transmissions. I miss the good old days when I could wake up and walk outside naked, reach down on the ground to that leaking spot under my Muncie, and say to the dog, "There's nothing like the smell of transmission oil in the morning." :thumbsup:


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## cij911 (Oct 25, 2017)

The Driven oil Paul recommended gets very good reviews as well (GL4)....


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## IdahoChevyMan (Jan 5, 2021)

devildawg said:


> I concur with cij911
> I would recommend Brad Penn grade 1 'classic' multi purpose GL-4 SAE 80w-90 gear oil. It's made specifically for old Muncie and Borg-Warner transmissions that require mineral base oils. This way your sure your getting a mineral base oil and NOT synthetic.
> Ive been running this in my Muncie M-20 since putting it in the vehicle and after doing extensive research on the subject. The chassis shop manual lubrication section for synchro mesh transmissions specify's SAE 80w multi purpose gear lube where available or 90w that meets the specification MIL-L-2105B. ( in other words GL-4 ) . GL = gear load . The transmission rebuild chapter says fill with SAE 90w. Bottom line is you want a mineral base lube. There are so many products out there it's difficult to determine whats synthetic and whats mineral base so thats why I recommend the Brad Penn.


You can never go wrong with Brad Pitt grade! 80/90 GL4 non synthetic it will be for my M21 Close ratio in the 68 Nova II. Thanks all and Happy New Year!


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## GTOTIGR (May 3, 2020)

Thought I would share my experience with using synthetics versus conventional oil in my 68 GTO Muncie. 

Somewhere between 4,000 - 5,000 miles ago/ ~15 years ago I had my original Muncie rebuilt to factory specs and decided to use Redline MTL All-Synthetic Formula. Those miles were all cruising not racing. 

I started feeling a slight grind when shifting from 3rd to 4th. All other gear changes were fine. 

I confirmed that the shift linkage was properly set and hadn’t changed, and that the clutch was properly adjusted. I then further read up on Redline synthetic oils (mind you 15 years had past), and I started to see some trends. As stated in this thread, the first was many saying don’t use synthetics in old/ Musclecar transmissions. The second being that Redlines MT-90 Full Synthetic is better for old transmissions and similar reported issues had been remedied by switching from the MTL to the MT-90. I purchased and installed the MT-90 ~ 9 - 12 months ago. Very slight reduction in the grinding but it was still there.

Four weeks ago I called the Redline tech hotline and was told that yes, while synthetic oil is more slippery than conventional oil and the the old synchro’s need a stickier oil, the MT-90 should still work fine in my transmission and that I may have other trans issues. He did suggest that I may want to try their MTL 75W80 Synthetic.

I read up on the Driven GO Conventional 80W90 Racing Oil, called the tech line, had a brief discussion with them and decided to order their oil. I changed the oil from the Redline MT-90 to the Driven GO Conventional. Today I took the car for a 50 mile drive and the 3rd to 4th shift grinding issue went away.

BTW, I had read several threads discussing how to remove the trans oil from a Muncie without a drain plug. There were many suggestions, including unbolting the trans from the bellhousing and spinning it until the drain hole was facing the ground. Another said drill and tap a hole in the lower section of the case that seems intended for a drain plug (apparently used on M22 trans). Of course it’s up to you... My approach has always been to use small diameter clear hose purchased at ACE Hardware along with a hand oil pump purchased from the auto parts store (picture enclosed). Knowing how much oil your trans holds will allow you to measure the oil extracted to verify that you’ve gotten the majority of it removed. Use the same pump to put the new oil in. Note that unless you have a lift, you’ll need to put the entire car up on jack stands so that it’s level in order to replace the oil to it’s proper level. With the car level I pumped the oil in until it’s starts overflowing from the fill hole.


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## Old Man Taylor (May 9, 2011)

I always used 90 weight dinosaur oil in my Muncie's. They sent me the oil to use with my 5-speed.


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## PontiacJim (Dec 29, 2012)

GTOTIGR said:


> Thought I would share my experience with using synthetics versus conventional oil in my 68 GTO Muncie.
> 
> Somewhere between 4,000 - 5,000 miles ago/ ~15 years ago I had my original Muncie rebuilt to factory specs and decided to use Redline MTL All-Synthetic Formula. Those miles were all cruising not racing.
> 
> ...


I don't know where the use of synthetic gear oil comes from with these older transmission and rear ends. I have seen this recommended as well. Bad idea as you found out. The later transmissions, like my S-10 or the Tremec 5 speed is designed to use the trans type fluids. Unless it states synthetic, then I would not recommend using it. They can be too slippery and too thin and not "cushion" the gears/synchros/bearings as needed.

I use the same pump for my S-10 to fill it and when I used to change the automatic trans fluid in my '97 Toyota, I used one of those inexpensive hand pumps with the long hose that you can snake down the dipstick tube, suck the old fluid out, and then refill with fresh.


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