[tiresmoke55]

Hey guys
Really quick question,

Long story short i just got a 89 chevy 1/2 ton 4.3 5-speed standard truck.

I was doing a oil change and what not on it so i decided to check the trans gear oil,, well the gear oil was very low, so i added some 80/90 gear oil to it like i would almost all chevy standard **** trans, didn't think nothing about it of course, Then earlier today i was talking to a buddy of mine and he said it didn't take 80/90 oil it took some weird name oil that was clear????

any thoughts on this,,,,,,, like i said its a 89 chevy 2wd 5-sp why would it take any different style gear oil??? I think my buddy might be messing with me but i figured i would ask........... any info would be great thanks always....

[1931 steve]

Your truck should have the Muncie 5 speed in it, and if it does it takes Synchromesh trans fluid GM part #12345349

Steve

[tnsmith10]

Originally Posted by 1931 steve

Your truck should have the Muncie 5 speed in it, and if it does it takes Synchromesh trans fluid GM part #12345349

Steve

muncie huh??? try new venture 2500-3500

[1931 steve]

Originally Posted by tnsmith10

muncie huh??? try new venture 2500-3500

According to Alldata both the 4 speed and 5 speed are both Muncie's, for a 1989 1500 2wd truck.

Steve

[tiresmoke55]

Originally Posted by 1931 steve

Your truck should have the Muncie 5 speed in it, and if it does it takes Synchromesh trans fluid GM part #12345349

Steve

Hello.
If this truck takes this kind of fluid and i put synthetic 80/90 in it,, what is the worst that kind happen? thanks

[runn141]

Originally Posted by 1931 steve

According to Alldata both the 4 speed and 5 speed are both Muncie's, for a 1989 1500 2wd truck.

Steve

1st time i ever heard of it

[1931 steve]

Originally Posted by tiresmoke55

Hello.
If this truck takes this kind of fluid and i put synthetic 80/90 in it,, what is the worst that kind happen? thanks

Chances are you will get harder shifts maybe some grinding, or nothing. If I were you I would drain and refill with the correct fluid. Just my .02

Steve

[runn141]

Originally Posted by tiresmoke55

Hello.
If this truck takes this kind of fluid and i put synthetic 80/90 in it,, what is the worst that kind happen? thanks

i put 80/90 weight in a transfer case that was supposed to have 50 weight motor oil and burnt it up. ive seen a transmission in a 1 ton chevy 5 speed that took a synthetic transmission fluid but maybe thats what the synchromesh is?

[Bumpstick]

Ok plain and simple take that 80-90wt out right away...

Its a close tolerance trans and it will over a period of time (fairly short) it will reduce the syncro`s to nothing...

Long before the GM trans fluid came to be they recommended either a quality 20wt motor oil or even 10-30wt and to this day (since the early 90`s) I have several running Mobil 1 10-30wt synthetic with less noise in 1st & 2nd and still going strong...

[Blazin72]

Originally Posted by Bumpstick

...to this day (since the early 90`s) I have several running Mobil 1 10-30wt synthetic with less noise in 1st & 2nd and still going strong...

Tiresmoke, it's always good to have a shop manual for your vehicle. I don't mean the Chilton or Haynes manuals either, I mean the factory manual for it. It'll tell you just about everything you need to know for your truck. I had an Isuzu Trooper that I was going to put 90w in as you did. I looked in the manual and it said to use 10w-40 motor oil just as Bumpstick mentioned. There could also be a sticker on the transmission itself. My Silverado has the sticker on the PTO cover and says to use the GM fluid (with whatever part number it is) or equivelant.

[sbchevfreak]

There could also be a sticker on the transmission itself. My Silverado has the sticker on the PTO cover and says to use the GM fluid (with whatever part number it is) or equivelant.

The oil for yours is unavailiable to the public by the original manufacturer, Castrol. This is why you must buy it from a dealer. Little inside tip, the same trans was used bt all the big three, and Chrysler sells it the cheapest.


The Synchromesh fluid is not the same, if you put it in a NVG4500, you'll kill it in a week. Both the Muncie, and the NVG3500 used the synchromesh fluid, so go to GM, grab about 4 quarts and do an oil change.

[tiresmoke55]

hey guys, thanks for the great info

My truck has over 220,000 miles on the tranny that is in it now. It did make a little noise, i stuck that 80/90 gear oil in it and all the noise went away, hmmmmm......i called the trans shop today and they said that they dont ever use that special syncmesh fluid and all it was was basically clear dextron/mercron ATF.......they told me that since the truck had so many miles on it to run a 50/50 mix of 80/90 gear oil and the rest in normal ATF fluid. What is your thoughts on this since my truck has over 200,000 miles on it? thanks alot!

[Bumpstick]

10=30wt Mobil 1, nothing else... Be happy...