We're getting ready to replace the transaxle fluid in my Fiero (around 120K miles) and I see there are two GM Syncromesh fluids.... the regular OEM syncromesh (ACDelco# 10-4006) and a Professional/Gold friction modified syncromesh fluid (ACDelco #10-4014). Which would be the better fluid to utilize?

THANKS

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JOE 4RE
'88 Fiero GT
Med. Red Metallic
loaded 5 speed

There are 2 types of GM Synchromesh Transmission Fluids:

Standard and Friction Modified which both are the same viscosity: SAE 75W-80

ACDelco 10-4006 is the 'standard' fluid, and the bottle also has (GM) 88900333 on the label.

ACDelco 10-4014 is the Synchromesh - Friction Modified fluid and the bottle also has (GM) 88900399 on the label.

Both fluids are 'Friction Modified', however the Friction-Modified version dosage has 5% more and has a friction additive for LSD clutch packs that require a GL4 fluid.

The standard fluid lacks the friction additive.

Read more on this thread from last year:
GM Synchromesh transmission fluid question by Rsvl-Rider
https://www.fiero.nl/forum/Forum2/HTML/147395.html

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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

quote Originally posted by Vintage-Nut: There are 2 types of GM Synchromesh Transmission Fluids: Standard and Friction Modified which both are the same viscosity: SAE 75W-80 ACDelco 10-4006 is the 'standard' fluid, and the bottle also has (GM) 88900333 on the label. ACDelco 10-4014 is the Synchromesh - Friction Modified fluid and the bottle also has (GM) 88900399 on the label. Both fluids are 'Friction Modified', however the Friction-Modified version dosage has 5% more and has a friction additive for LSD clutch packs that require a GL4 fluid. The standard fluid lacks the friction additive. Read more on this thread from last year: GM Synchromesh transmission fluid question by Rsvl-Rider https://www.fiero.nl/forum/Forum2/HTML/147395.html

V-Nut, thanks for the link to the more in depth thread. So it sounds like the standard Syncromesh (10-4006) or equivalent should work fine in my stock '88 GT?


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JOE 4RE
'88 Fiero GT
Med. Red Metallic
loaded 5 speed

[This message has been edited by JOE 4RE (edited 10-21-2024).]

quote standard Syncromesh (10-1014) or equivalent

I believe you mean ACDelco 10-4006 and yes, it should work fine in a stock '88 GT.

And of course, the link has members opinions and comments....

quote Originally posted by Vintage-Nut: I believe you mean ACDelco 10-4006 and yes, it should work fine in a stock '88 GT. And of course, the link has members opinions and comments....

CORRECTED... thanks

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JOE 4RE
'88 Fiero GT
Med. Red Metallic
loaded 5 speed

The synchromesh fluid required in the Getrag is GM part number 89021808
The USA number is 12345349
I believe that was the old number.
The other member has the updated GM number.
88900333

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fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

Yes, GM changed synchromesh part numbers over the years....

The 'Newest' GM number is 88900333 for 'Standard' Synchromesh in the USA, which formerly was 12345349

And Canada and USA have different GM / ACDelco numbers; Canada is 89021808