Firebrian

I'm using the GM Manual Trans/Xfer case fluid as well. Except for the first or second 1-2 shift in 40-50 deg weather or below, I don't feel much notchiness at all. It's entirely gone after about 3-5 minutes. Feels no different than the Valvoline Dino ATF I used the last time around.

pozesd99'

iTrader: (3)

Have always used amsoil torque drive. Just got the redline d4 atf in. Excited to try it out. Clutch should be going in this weekend so i get to report back shortly!

2000ls1jeremy

I use same in mine

Boxxx

Forgot to update the thread, I had a few days in the 30's and 40's and there wasn't any notchiness in the shifts but it was slightly firmer in feel as expected until it warmed up some and then it was like any day 70 or above. Much less drastic than any gearbox I've used filled with 75-90W gear oil.

mac62989

iTrader: (1)

Emailed Tremec and got this response:

Hi Matt,

First, thank you for purchasing one of our TREMEC brand products.
The fluids we recommend for the T-56 transmissions are the Dexron iii/Mercon ATF or the Mobil 1 synthetic ATF. The synchromesh fluid is used specifically for our TKO series transmissions.
Hope this helps!

Boxxx

Also I don't know why it didn't occur to me to until now but the LT1 T-56 was made by Borg Warner so I don't even know why I'm in here.

BALLSS

Tremac bought Borg Warner transmissions in 1998 but nothing changed inside the T56 until Tremac came out with the 6060

Tremac did however start using the carbon blocker rings in the T56 for units they built for the 94-97 LT1 applications after 1999 IIRC and the T56 for the LSx applications. I bought my "new" LT1 T56 in 2005 and D&D said it had carbon blocker rings in it. Still had the DEX3 label on the side of the tranny. D&D said Tremac only tested DEX3 and later Mobil 1 in the T56 but not every fluid brand out there so DEX3 or Mobil 1 are the only fluids Tremac will endorse as it was explained to me by D&D

My trans case has the BW name cast into it as well as Tremac

Firebrian

If you have the cellulose lined blocker rings in your T56 (1998-2000 for LS1) then your fluid options are much more limited. From 2001 and later they should all be carbon. Haven't spent much time researching LT1 T56's but I don't see why those all wouldn't be the paper lined rings/synchros as well. On the last page I listed a number of links on these topics including fluids.

Boxxx

I think he was talking about later replacement transmissions. As far as I know and from what I've read an original LT1 T-56 would have paper lined which is why I just went with the GM MTF as suggested, I knew it'd be safe and I'm the "better safe than sorry" kind of person. At any rate I've been happy with how it's been performing so it's what I'll continue to use even if I have to change it out more often.

dojob

Just changed my '00 with 18k mi, figured 17+ yrs on original fill. Should be changed out, so no issues occur. Always shifted smooth. Want to retain that.

Used 4qts of Castrol Domestic Multi-vehicle (ATF) Automatic Transmission Fluid yesterday, form Advance Auto:
https://shop.advanceautoparts.com/p/...hTerm=castrol+

Drove around town last night, feels notchy and catchy in between gears

Now I ordered ACDelco Manual Transmission Fluid 888618008 from Summit. Switching to that, once it shows up:
https://www.summitracing.com/parts/ado-10-4033

Wanted this initially but Tremec's site just says any general DEX III. That's not the case. That Castrol feels awful.

dojob

CONFIRMED:

ACDelco Manual Transmission Fluid 888618008 is smoother than the original fill i drained out on 2 days ago and way better than the Castrol DexIII that I drained out today.

Disengaging the existing gear and engaging the next is smooth and cushioned. Shouldn't of doubted myself from the get-go and just bought this to begin with.

RevGTO

iTrader: (12)

I mentioned earlier in this thread how I replaced the original fill on my 01 T/A with M1 and got the same symptoms. My current M6 has 91k and, as far as I know, is on the original fill and shifts like a hot knife through butter. My take from the earlier experience: it ain't broke and I'm not fixing it. Just leaving it alone for now.

Firebrian

On original fill, Dex3 conventional at 90K miles would have likely sheared down to 4 cSt or lower from the original 7.0-7.5. Maybe even down 3.0. So no question that would feel a lot less notchier on the cold shifts than a fresh fluid with a 7 cSt viscosity.

In any case 3-4 cSt at 100 deg C is pretty darn thin fluid to be protecting gears and bearings at high temps and stress. Those factory fill Dex 3's from 15-20 yrs ago probably had much stronger add packs than today's Dex 3's. So that counts for some additional anti-wear protection. For today's conventional Dex 3's I don't even feel comfortable going over 5K miles on them (sheared down to 5.5 cSt by 8K miles in a T56). The synthetic ATF's do a lot better. You might get 20K-30K miles out of them before they shear down to under 6 cSt. Changing conventional ATF fluid more often is not a big deal. If you read enough threads on transmission fluids you will run across people who had problems with most any of the synthetic fluids, and some of the conventionals. Still haven't found one that said the GM/AC Delco 88861800 manual transmission fluid/ATF gave them problems.

AnotherWs6

iTrader: (17)

You'll change it when it blows up, that way no wasted money.

I know people who are religious about changing fluids in transmissions and rears and can still have problems. I changed the rear fluid in my truck for the first time in 250K miles. Fng blew up a couple of months later. Who knows with this stuff. Seems like a lot of luck.