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