Muncie M21 fluid?

[Rat407]

I was wondering what synthetic fluid would be good to use in my muncie. I have a 65 Impala and right now I'm using regular 80w-90 weight.

I'm not sure of what to use. I don't have an owners manual and the question just came to me since I was on here reading about tranny fluids.

I was wondering if the GL-5 would work? Right now I need to get it resealed. It has sat for months at a time with little use and the seals have dried up some. I plan on using it now on a regular basis and was wanting to install synthetic. Any suggestions?

Thanks

 

[plexx]

I had that tranny in my camaro years ago (converted it from an auto to the muncie).I know that this tranny likes the oil to be alittle on the thick side, no less than an 80w90.I don't know if I would go synthetic in this unit since it is an older tranny and a very heavy duty unit, the regular dino 80w90 would do you fine,worked fine in my camaro for many years and many VERY HARD miles. Hope this helps.

 

[goatdude]

I have used dino GL-5 oils, dino GL-4s and Red Line MT-90 in my Muncie. The Red Line oil shifted the cleanest and over time stayed that way vs what I felt was a decline in shifting ease with the usual GL-5 "80W90 gear lube". NAPA sells a GL-4 that also works pretty good but my vote is for the Red Line MT-90.

 

[pgtr]

I believe 'SAE90 GL5' (80 for cold) was originally the factory spec years ago and perhaps was factory fill. Your original owner's manual or factory service manual from the 60s or early 70s would say this. But nowadays I keep reading about GL4s being the way to go for manual transmissions requiring a gear lubricant. Not just for metal compatibility (I believe the Muncies use bronze synchros and modern GL5s aren't so bad?) but also matching the friction needed to best allow synchros to optimally operate.

Here's a few I've run across and would consider:

Regular GL4s:
-CRC/Sta-Lube 85W90 GL4
-Pennzoil GearPlus 80W90 GL4


Synthetic GL4s (only):
-Pennzoil Synthetic 75W90 GL4
-Redline MTL(70W80 GL4), MT90(75W90 GL4)
-Amsoil 80W90 Marine GL4


Regular GL5s:
-Castrol HypoyC 75W90 or 80W90 GL5
-Havoline 80W90 GL5
-Exxon Superflow 80W90 GL5


Synthetic GL5s (incl combos):
-Mobil1 75W90 GL5
-Valvoline Synpower 75W90 GL5
-Castrol Syntec 75W90 GL5
-Redline 75W90NS GL5
-Royal Purple 'Max-Gear' 75W90 GL4/5 combo
-Amsoil (2 types?) 75W90 GL4/5 combo


Other(?):
-GM Synchromesh???
-ATFs???


===========

What's best? Dunno. On 'paper' I'd guess the RL MT90 or Pennz GL4 Synthetic? I've NEVER seen any Pennz gear lubricants and have NO idea where these can be purchased. RLs can be had though it may be necessary to scrounge a bit locally or order online. I'd also guess the regular (non-synthetic) Sta-Lube and GearPlus GL4s to be good candidates as well.

Despite what I've heard about GL5s now purportedly being suitable in some cases for manual transmissions w/ 'yellow' metals (I presume that includes bronze?) - I just seem to be a little reluctant.

I've not heard any conclusive recommendations for either an ATF or one of the various 'synchromesh' lubricants like GMs. I'd expect them to be too light and leaking to be a problem perhaps?

I'd like to hear more what what works and, perhaps more importantly, what does NOT work in reality (not on paper) in old Muncies myself...

 

[sbc350gearhead]

I use RP Max-gear GL-4 GL-5 rated fluid in my BW super T-10, and it seems to work great. It is the only synthetic that I have used in it though. I am sure that the amsoil and redline would work just as well though.

 

[Rat407]

Thanks pgtr. I might try the Redline, not sure. I need to do a few things to the car other than tranny seal replacement. I wonder if Auto RX would work for me on this instead of replacing the seals? Just a thought. Might ask Frank.

Thanks everyone else for the info. I miss driving the 65 big block but with gas so high and 8mpg it just isn't cost effective right now with other bills to pay.

 

[JohnBrowning]

The early Corvettes that came with Muncies had a whale ester based fluid in the transmission and in the rear diff. THe cloest I have found to replicateing this fluid is with Redlines MTL. I have alot of Corvette customers that are very happy with this combination in their Muncie!

P.S. I do not sell any lubricants. I just tested a lot of lubrivcants looking to make my customer happy!

 

[pgtr]

quote:

---

Originally posted by JohnBrowning:
The early Corvettes that came with Muncies had a whale ester based fluid in the transmission and in the rear diff. THe cloest I have found to replicateing this fluid is with Redlines MTL. I have alot of Corvette customers that are very happy with this combination in their Muncie!

---

Huh!?

Can you provide more details or info on this whale oil GM used specifically in Corvettes?

Corvettes ran Muncies from about '63 or so up til about '74. Which ones are you referring to as early? '63-'67?

What about all the Muncies destined for millions of other GMs besides Corvettes. They didn't get the whale stuff?

GM manuals from 'the day' I'm familiar with simply list "SAE 90 GL5", nothing special.

The MTL is a bit light for a Muncie 4 speed IMHO. I think MT90 might be a better option. But if the Muncie is new or rebuilt or whatever the MTL (or GM Synchromesh) might be worth a shot. If it doesn't leak out, it might produce easier shifting in a Muncie. But the Muncie was originally made for a heavier oil in mind like an MT90 and benefits from a good quality GL4 (like Redline) from what I can tell.

============

You mentioned that MTL is the closest substitute you found for this purported "whale ester based fluid ...[used]...in the rear diff." I presume we all know this but it's worth repeating perhaps... MTL is NOT for differentials and as a GL4 will potentially ruin ring/pinion gear set in short order!

============

As to this claim of '63-? Corvettes running whale based oils in both their boxes here's my thought on it based on what little I know...

Back in the 60s GM's Positrac additive did contain among other things some element of whale oil I'm told. Whaling has long long ago fallen out of favor. Not sure exaclty when but sometime in the 70s I believe GM finally found a substitute ingredient for their Positrac (limited slip) additive. You can buy their additive at any dealer and it's good stuff. It's one of the better LSD fluids out there and quite popular w/ many car crowds, not just the Chevy types.

Most modern differential oils include a friction modifier for LSDs making such additives unnecessary. If you purchase one that doesn't have it and need an LSD friction modifier, you can use GM's or whoever's separate additive. I suggest sneaking up on it. Add a few ounces at a time to the diffential fluid until all chatter is gone. Most folks report that thigns quite down between about a 1/2 bottle and 1 bottle (2 max, these are VERY tiny bottles last I checked, maybe 6 oz) but as always YMMV.

But again, I don't see much need for that approach. Every modern GL5 oil that states it's for limited slip differentials has always worked fine in LSDs as is w/ no clutch chatter in my limited experience.

The GM additive was and is not specific to early Corvettes and was for any GM sporting an optional 'Positrac' and works fine in any other makers LSD as well. Positrac was not standard on Corvettes until about '70 or so though it was an overwhelmingly popular option by then.

This GM additive has nothing to do w/ Muncie 4 speeds.

 

[JohnBrowning]

First I did not say that it contained whale oil outright. What I said was that the esters used in the lube were whale based. Most products in the 50-late 60's had whale based oils or esters in them. ATF, premium gear lubes, lib stick, make up foundation, cleaners, and some oil additives just to name a few items that had either whale oil or esters derived from whale oil. I know for a fact that the positrac unites this in use.

THe Muncie conection was what I was told by a gentleman that rebuild them. Seeing how he had been doing this longer then I had been alive I took him at his word. It also made sense since most muncie did not have the shift quality that the owners reported the car to have when new.

In private testing we found that the MTL recreated the feel of the origanal OEM fill as reported by the origanal owners of the cars. THe only thing different between the Redline MTL and all of the other products we tested was the huge percentage of synthetic esters. This lead me to belive that the old Tranny Tech. must have been right about the whale esters.

So my statement about whale esters in the Gear Lube come from a combination of word of mouth from old timers and my personel observations on modern quest to find a replacement lube for the origanal.

I am not trying to rewrite Chevy by the Numbers.

 

[pgtr]

quote:

---

Originally posted by JohnBrowning:
First I did not say that it contained whale oil outright. What I said was that the esters used in the lube were whale based. Most products in the 50-late 60's had whale based oils or esters in them. ATF, premium gear lubes, lib stick, make up foundation, cleaners, and some oil additives just to name a few items that had either whale oil or esters derived from whale oil. I know for a fact that the positrac unites this in use.

---

OK. Your original statement sure made it sound like this whale oil was something specific to early Muncies as installed in Corvettes. Compared to the millions of manual trannies of the same basic design at the time not to mention the millions of muncies installed in other GM products - didnt' quite follow what made early Corvette muncies special w/ respect to large water going mammals.

quote:

---

Originally posted by JohnBrowning:
THe Muncie conection was what I was told by a gentleman that rebuild them. Seeing how he had been doing this longer then I had been alive I took him at his word. It also made sense since most muncie did not have the shift quality that the owners reported the car to have when new.

---

Oh come on now! You're older than that aren't you? COnsidering Muncies only appeared in Corvettes in '63 or so and didn't start getting rebuilt in a common or widespread fashion until the 70s or so.

quote:

---

Originally posted by JohnBrowning:
In private testing we found that the MTL recreated the feel of the origanal OEM fill as reported by the origanal owners of the cars. THe only thing different between the Redline MTL and all of the other products we tested was the huge percentage of synthetic esters. This lead me to belive that the old Tranny Tech. must have been right about the whale esters.

---

Well I don't know which product(s) you compared the MTL to but regardless I can assure you that MTL is quite unique for several reasons:
A) It is the only lightweight 70W80 GL4 on the market period.
B) It's one of the very few GL4s on the market.
C) And it's one of only 2 or 3 GL4 gear lubes that claims to be synthetic.

When you say that the success you had w/ the MTL was due specifically to it's "huge percentage of synthetic esters" why do you discount these other differences outright?

The Muncie owners I've spoken to have cited MT90 as a general preference. Yet others have noted that Muncies are tolerant of varoius lubricants, even GL5s or 'combos'. Many Muncie rebuilders themselves have only suggested MTL specifically if a fresh quality rebuild has been done but not necessarily on an older, worn unit.

quote:

---

Originally posted by JohnBrowning:
So my statement about whale esters in the Gear Lube come from a combination of word of mouth from old timers and my personel observations on modern quest to find a replacement lube for the origanal.

---

The only thing I can corroborate for you is the whale oil link to the old 1st generation GM positrac additive that is long gone but was replaced an an equally effective incredient back in the 70s.

I can also add that many manual transmissions on the road today from the 70s, 80s, 90s and made on various continents, not just Muncies from 63 or so as installed on Corvettes do in fact suffer from less than like-new perfect performance because manufactures don't insist on specing GL4 or owners don't care to install GL4 and settle for the much more prevalent GL5's sold at any supermarket.

quote:

---

Originally posted by JohnBrowning:
I am not trying to rewrite Chevy by the Numbers.

---

But you are going on the subjective memory of someone that drove a car back in the summer of 1964 or spring of 1966 as your measurement standard.

I submit that a freshly blueprinted M21 w/ MTL may very well shift better than a visit in a time machine to a '65 fuelie did the day it left the dealership. Especially on a cold January morning. Who's going to prove me wrong?

I think we are at least mostly in agreement on the conclusion of MTL though I think it's better left to a fresh rebuilt like new unit myself. I just don't agree w/ the reasoning leading to the conclusion nor do I consider MTL the only show in town for Muncies. And I fail to see anything unique about Muncies installed in Corvettes from the 60s over many other applications. In fact I'm not even sure Muncies intended for Corvettes had unique casting numbers - would the folks in Indiana have even known a given unit was destined for Corvettes and used the whale stuff over the other junk?

thanks,

 

[Bror Jace]

I'd be reluctant to go with a thinner weight unless you are willing to have it rebuilt regularly. If using Red Line, I'd use their GL-5 75W90.

In addition to the fluids previously mentioned, I'd be tempted to try the Schaeffer blend 80W90 gear oil:

http://www.schaefferoil.com/data/267.html

or even their full synthetic version:

http://www.schaefferoil.com/data/740-741.htm

Corrosion is NOT an issue with the Schaeffer oils and they are available by the quart from Tim Mills, a sponsor on this site.

The Chevron gear oils might be available in your area and would be worth investigating. Probably comparable to Penzzoil ... really good stuff.

--- Bror Jace

 

[pgtr]

I agree Bror and I didn't mean to imply I was recommending MTL - I'm only mentioning it w/ hesitation and qualifications. Hands down the Muncie likes the 75W90s. This is where most folks that work on Muncies seem to to be as well. These are obviously venerable and old transmissions - all the more reason for a 90. Is that Chevron a GL4 by chance? Last I checked it wasn't but I'm not sure off hand. I know I'm pretty stuck as being biased towards GL4s in manual trannies but many Muncie owners seem pretty happy w/ GL5s or GL4/5s. Like the Chevy SB itself, this tranny seems pretty 'flexible'

thanks,

 

[JohnBrowning]

THe only vechiles with Muncies that I have worked with extensively are Corvettes. It is hard to find older muscle cars that came with muncie trans that still have the origanal trans in them. It is even harder to find on with the same owner that bought it when it was new. Corvetts are about the only car that you run across routinely with the above combination!!

Whale esters and whale oil were common place in automotive fluids of the period! It is considered common knoldge tht early ATF trany fluid made extensive use of whale esters! THey used whale esters back then for the same reason we like to use Polyo ester base stocks today.

Even things as mundane as compass's used whale oil and Walres(sp) oil in latter years. Now they use kerosine which does not work as well.

P.S. I am only 30 years old. If it makes you feel better one of My mentors when I was an aprentice was an aprentice himself under Hilter third reich! He started his aprenticeship with BMW aircraft power plants.

[ September 27, 2003, 11:34 AM: Message edited by: JohnBrowning ]

 

[pgtr]

JohnBrowning,

I didn't mean to drag your age out - sorry 'bout that - in all honesty you seem knowledgeable beyond your years and I mean that as a complement.

BTW do you work on Muncies much yourself in general or as a hobby or what?

thanks,

 

[JohnBrowning]

pgtr, I am not upset! I like talking to people! I like history a lot. I have always tried to find people that knew what I wanted to know and then either modeled them or worked for them. You can learn alot from someone when you break bread with them. I often found that you could learn more over a beer or a dinner plate in friendly conversation then you could at the work place. Try it some time. The hardest part is breeching the gap and listening. One you learn to bridge the personel /professional gap and you learn to listen alot of people will share what they know for nothing at all.

Do not take my brevety as hostility. I am not a good written comunicator with out spell check so I will always try to make things brief!!

I have worked on my share of manual transmissions but would not call myself a SME on Muncies.

[ September 28, 2003, 12:18 AM: Message edited by: JohnBrowning ]