ctjackster

some of my synchros are starting to act up, thought I'd try some fresh tranny fluid before major stuff - what's the consensus on good modern oil product for my 65 (original) Muncie?

TIA

Donald #31176

I had my BW T-10 rebuilt about 4 years ago and Tony s Corvette Shop
in Md. recommended using a synthetic gear lube called "Hydro Shift".
Shifts like butter and no leaks.

SWCDuke

The original spec was Mil-L-2105D. The modern equivalent is SAE 80W-90 GL-5 gear oil - same as what is recommended for virtually all hypoid gear axles.

Duke

66BB

Jack,

It sounds like you may be up for a rebuild. Mine is out of the car now along with the engine, all being rebuilt. I should have it back in about a month and let you know how it comes out.

Marty

Subfixer

Looks like the list for this winter is growing..... I may have to move in for a week or so.....

ctjackster

Marty - I was JUST going to email you and ask how the repaint was going, and ask if the "while-I'm-at-its" had set in - we still need to cath up, maybe take the boys tubing next weekend (not using my boat enough, and it's your job to help!). What else has been added to the list of things on your car? How is the repaint progressing?

Paul, yeah, I was gonna sneak that one in on you, I need it to get through the summer (without surgery), I was just aksing an old mechanic last night "hey how hard is it to fix a synchro?" (he said it was simpy! - yeah right) and since that is a tranny-dropping exercise, I thought hmmmm, pull the tranny, fix some synchros, change the clutch (oh and swap in solid lifters and LT1 cam) while Paul is over!

I agree that list of things we are going to tackle is getting pretty long . . . . may have to have you along for the cam thing, and have at the tranny / centerforce clutch project by my lonesome.

Corbrastang

I've been using Moroso 80 weight climbing gear oil. No problems

StrayDog

I installed a drain plug in my 66 Corvettes muncie & changed the fluid to a synthetic (had no problems with tranny prior) just figured draing the fluid after so many years was a good thing....... shortly after a slight grinding / or crunching noise began when shifting to second gear................switched back to conventional 80/90 & the noise gradually went away after a few hundred miles...has not recured...just thinking the Muncie was designed for conventional transmission oil.......................just my 2 cents.....

ctjackster

really stupid question - how do I drain the fluid from the Muncie tranny? Just looked at the shop manual quickly thins morning before leaving for work, didn't find a quick answer for a dummy mechanic.

StrayDog

heres what i did.on the lower side of the transmission is a raised area Boss as i will call it ....I drilled a approx 1/2 inch hole.... the fluid will drain out taking all the alum drilling debris with it............then I tapped the treads to accomodate a pipe plug ( put grease on tap to hold particles) then installed plug.you will see the area or boss that is there for said plug in the first place,,,.apparently GM didnt install plug & saved 35 cents back in the olden days..........35 X 80,000 anyways a easy job......worked for me...Woof

ctjackster

Sounds like a perfect solution and one that I might explore, but let's assume for the moment that I didn't drill and tap a drain hole - how do folks drain it - is this like my diff, will I be "evacuating" the fluid?

StrayDog

Yes ........but the gear oil is thick so do it when its warm easyer to draw..................

JohnZ

You'll need a suction pump with a length of flex tubing on the end to empty it through the filler hole; same thing you use to empty and refill the diff. Most auto parts stores have inexpensive plastic pumps.

Plasticman

You would be better off adding the drain hole / plug.

That way you would be removing the chips and debris from years of wear & "work". Otherwise, those chips & debris just keep wearing the internals even more.

Might even think of adding a drain plug with a magnet on the end.

Plasticman

SWCDuke

Don't drill any holes unless your name is Bubba. Just use some rubber tubing to siphon out the old oil. My T-10 has a drain plug. The T-50 in my Cosworth Vega does not, so I just siphon it out.

Duke

ctjackster

ok, I certainly have my answer - there is no oem drain plug (I knew that) and no bolt that can be removed that drains the Muncie, I have to suck the oil out like I did with my rear rear diff - I am familiar with that process. As for the drill and tap a hole idea, I can see the wisdom if I was going to be draining the thing quite often, which I won't be. I also have the original engine and tranny in the car, and tend to avoid doing things that would irreversibly harm originality, so I am likely to just grin and bear it.

Thanks for all the quick advice, all of which is appreciated.

ctjackster

ok, just to update this thread - drained the Muncie last night (all my best work gets done after 10:00 when the little kids are in bed) using my oil sucker that usually gets used for oil changes in my boat. I was kind of excited at first because the fluid was a bit low in the tranny to begin with. I say excited because I was hoping the old or inadequate oil level was the cause of some recent synchro noise. Replenished the fluid with the non-syn gear oil. Dropped the car back down off the ramps & stands, took it out for the test drive to check on the shifts in and out of third (the problem before) and . . . still acting up though not as bad. And the shifts themselves are all smoother now, when not encountering the buzz in and out of third, which is quite intermittent.

Looks like I am gonna limp it through the rest of the summer and then have to do something in the fall.

StrayDog

my thoughts exactly........ usually I just read posts & dont say much,>>> as when you do make a suggestion your called a BUBBA..the intent of the Forum is to give other Corvette owners suggestions on what may or not have worked for you & let them take it form there ...........Woff the Dog

ctjackster

hey I didn't call anyone Bubba - if it wasn't an original, VIN stamped tranny I think it would be a good idea (tapping a drain plug)

SWCDuke

A homemade drain hole does not guarantee that an chips in the bottom of the trans will drain out. A magnetic fill plug is the best way to trap ferrous chips. Most non-ferrous chips will just stay at the bottom until you take the trans apart.

Duke