When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Looking to change out the fluid in my '02 T56, it calls for GM 88861800, ordered some as I have previously from Amazon but received GM 19540137, did some searching and apparently it is the replacement part number but several things I have read suggest not using it in the older T56. Thoughts?
Looking to change out the fluid in my '02 T56, it calls for GM 88861800, ordered some as I have previously from Amazon but received GM 19540137, did some searching and apparently it is the replacement part number but several things I have read suggest not using it in the older T56. Thoughts?
Is the 19540137 thick like gear oil? Google says it’s a 75w80 which is way thicker than 88861800, so you don’t want to use that if that’s what it is.
88861800 was an automatic transmission fluid (Dexron III) so an ATF labeled Dex/Merc will have the same or close to the same viscosity index as the 88861800. There are some fluids that say they are compatible with Dex III (Valvoline Maxlife) but it’s thinner than Dex III. It’s closer to the same viscosity as Dexron vi which is what replaced GM replaced Dexron III with as far as ATF goes. Dexron VI is a “low viscosity” (LV) fluid where as Dexron III was not. All of this being said I bet almost any automatic transmission fluid would work. But I wouldn’t use 75w80 gear oil.
*Edit*
I’m basing “betting that any ATF will suffice” on the fact that I’ve used Synchromesh ATF (not Royal Purple) in a T5 that called for Mercon and there weren’t any ill results. There wasn’t anything to write home about either though. It performed the same with the cheaper Dex/Merc.
Last edited by Y2K_Frenzy; Sep 2, 2025 at 08:02 PM.
Thanks for the feedback, I called two local Chevy dealers and asked if they had GM 88861800, one said no, they other said they had GM 19540137 which was the new part number. I have not opened one of the bottles to see what the viscosity is like.
Ah ha! I think now maybe we’re getting somewhere as far as why the thick gear oil type fluid superseded a Dex III type fluid. Maybe since the AR5 was more mass produced than the T56 after GM no longer licensed Dexron III for use in GM vehicles (GM 88861800) they only wanted to market one manual transmission oil. So instead of bottling up some Dex VI ATF and calling it “T56 Fluid” they just went with what they’d sell more of instead of paying two different bottling co’s.
Tremec switched to carbon vs paper blockers in early 2000's for the T56. Paper and synthetics did not get along. Carbon its not a problem. Me, I use D3 even though Tremec verified my 05 built trans has carbon....sticker on side of my trans says D3
The AR5 is an Aisin trans like all the Toyotas / jeep / etc, where the T56 is a Borg-Warner / Tremec trans. Most B-W & Tremec trans are ATF. All Aisin manuals are gear lube
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
T56 fluid ? 
