I'm running mobil 1 5w30 in my 5 speed and it seems to shift a little notchy and it's easy to blow shifts under hard acceleration.

Is that oil too thin for the synchronisers to work correctly? And if so what would be better? I want to stick with a synthetic

I saw some mobil 1 gear oil in the store but it was really a heavy weight and about $8 a quart. Would that work better and be worth the expense?

GM recommends their 12345349 Synchromesh transmission fluid. That is what I have and there are no problems. You need one quart.

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If it doesn't leak, GM Synchromesh Fluid (was about $8 a quart several years ago). Available at GM dealerships. Since it's what GM recommends, and is about the same cost as the other stuff you mention, I would use the Synchromesh Fluid.

Now, if my axle seals (or whatever) were leaking, and I wanted to get by on something cheaper until I could fix the leak, I'd be using plain old 5W-30 engine oil. Reason: That's what GM recommended for use in the Getrag, before they changed their recommendation to Sychromesh Fluid.

...but that's just what I'd do

[This message has been edited by StuGood (edited 06-22-2001).]

I use the 5/30 and mines shifts just fine how ever I dont ever beat on it either. but this is the first Ive heard of the syncromesh oil I might have to go and gets me some too.this new earl sounds really smooooth.

I have used both the GM recommended oil and synthetic 5w30. And I found the GM oil worked best. With the 5w30 the shifts were not smooth and it was tough getting it into first gear at stoplites. With the GM stuff the shifting and first gear problems went away.

Pennzoil makes synchromesh fluid for $4.00/ qt, works great. I got mine at a local quick lube that is a Pennzoil dealer, they sold me all I wanted.

Synthetic engine oils can be too slipery for use in manual transmissions. Synthetic transmision lubricants usually have aditives to increase friction and help the synchros do their job. GM Synchromesh is a good choice. I have always had good experience with Redline MTL.

I got the GM synchromesh.

$15 a quart!!!!!!!!!!!!!!!

And contrary to one of the above posts, the getrag 5 speed takes 2 quarts not 1.

It had better be worth it.

2.7 quarts, according to my Haynes manual and my dipstick.
I've always run 5W-30 Havoline, regular or synthetic, makes no difference IMHO.
I'll try a bit of the GM synchromesh next changeout. It's always been a bit notchy. PFF is the first place I ever heard of using the synchromesh fluid.

Can the Syncromesh and 5W30 be mixed ok? You'll still have about a pint of fluid in the tranny after draining (I found this out when I split the case on my Getrag!). I want to switch to the Syncromesh but wasn't sure if there were any special precautions to take to flush out the old fluid.

According to the chilton manual, and the original 88 fiero owners manual, the getrag takes 4 pts which is 2 quarts.

The Izuzu 5 speed takes 2.7

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88GT 5sp, in desperate need of an LT1
http://www.geocities.com/fiero88gt1/

The best stuff is http://www.redlineoil.com/redlineoil/mtlti.htm My car shifts smooth and nice with this.

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Josh (known by TheFiero64 for first 1239 posts)

My pics

Update:

Been 3 days with the synchromesh and so far it's very impressive. No blown shifts, no problems getting into 1st at stoplights.

It's like a whole new trans. Shifts are solid and precise.

2 thumbs up!

I have used Mobil 1 for more than 5 years now. I'll try that to see if I can have a new tranny too

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Alex4mula

Update too

Changed oil yesterday ($9/qt!). Right away I felt it smoother while cold. Drove today to work (16 miles) and overall I could say it feels better. Good improvement for $20! TKS.

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Alex4mula

I second, er... third, er.... Well....

At 100K I changed the Muncie's tranny fluid to Mobil 1 5W30. I wasn't easy on it, nor did I constantly beat on it. I also agree with the statement, "It was always a bit notchy," and it didn't change, leak, or otherwise behave like I had to worry about it after the change.