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.
While looking high and low for a definitve answer to the correct fluid in the nwc t5, I remembered I had an original 1987 factory service manual in the garage. Atf may be acceptable alternative in some people's opinion, but here it is black and white. Moderator do what you wish with this information since the sticky claims otherwise.
While looking high and low for a definitve answer to the correct fluid in the nwc t5, I remembered I had an original 1987 factory service manual in the garage. Atf may be acceptable alternative in some people's opinion, but here it is black and white. Moderator do what you wish with this information since the sticky claims otherwise.
Dextron 2 is atf, probably can’t find it anymore. I’m sure dex 6 would be better
That whole question and the answer in the manual is PURE CRAP.
GM's (and every other customer that bought the T-5) recommendation for fluid, changed from year to year, with NO CHANGE WHATSOEVER to the underlying parts.
I'm no expert, merely an interested observer although with MANY decades of experience as a design engineer dealing with corporate dumbassitude. Vorteciroc on this forum, who worked for GM in that same capacity as a powertrain engineer, can probably be more definitive re. GM in particular and how they did things. Butt it seems to me, that EVERY SINGLE YEAR (and it was YEARLY, not quarterly, or alternate years, or on any other schedule), GM brass hats had a big "conference" of some sort, where the various "interested parties" would come to argue such points. So, you had the engineers (ALWAYS lowest on the decision-making totem pole and NEVER listened to), raw bean counters (production cost), warranty admin dept, govt regulations compliance such as CAFE, the marketing dept, and so on. Each of these constituencies has a point of view and AGENDA. Some years, it seems like either the next-higher-level-executives (download GM's org chart sometime: it'll make you PUKE) either had some turnover so they got new people in positions of power with different opinions, or different ones were disgraced, or owed some other faction a favor this year, or some other equally non-technical concern would dominate the decision. Meaning, there was NO CONSISTENCY and NO RATIONALITY in the "decisions" they made. So, one year, the warranty dept would win, and they'd advocate for a gear lube type of transmission fill; then the next year the CAFE dept would win, and they'd advocate for the thinnest (least drag) fluid fill; the next year the accountants would win, and they'd advocate for the cheeeeeepest possible thing they could buy that could masquerade as "fluid" and still get through the warranty period with few enough failures to appear profitable; and so on. Meanwhile, in EVERY year, the EXACT SAME gears, the EXACT SAME bearings, the EXACT SAME seals, the EXACT SAME synchro clutch rings (brass, in the 1st design T-5), the EXACT SAME bushings, and so on, all assembled to the EXACT SAME tolerances, were being supplied to GM, BY AN OUTSIDE VENDOR (Doug Nash, using Borg-Warner as their contract mfr), according to THEIR design specs, and whose own fluid spec GM chose to override at their own discretion.
And GM's "recommendation", viewed in that light, means ... what?
The 1st design (87-back in our cars; different year range in some others) has straight rollers, brass synchro rings, and so on. 60s / 70s stuff. ALL of those parts need a relatively thick lube, but not like the old 50s 95W-140; 75W-90 or 80W-90 is just about ideal. ATF is too thin: the countergear bearings IN PARTICULAR, one of which is THE SAME PART # as the axle bearings in your 10-bolt, will GRIND TO POWDER with lube that thin, much faster than if the proper lube is used. Try filling your C-clip rear axle with ATF and see what happens to the axle bearings.
Ignore the unvarnished unmitigated unadulterated unalloyed CRAP you see in the manual on this matter. Use synthetic 75W-90 such as Mobil1.
Last edited by sofakingdom; 04-24-2024 at 09:47 PM.
ALL of those parts need a relatively thick lube, but not like the old 50s 95W-140; 75W-90 or 80W-90 is just about ideal. ATF is too thin: the countergear bearings IN PARTICULAR, one of which is THE SAME PART # as the axle bearings in your 10-bolt, will GRIND TO POWDER with lube that thin, much faster than if the proper lube is used. Try filling your C-clip rear axle with ATF and see what happens to the axle bearings.
That's weird. My counter shaft bearings never "ground to dust" using the recommended ATF. None of the bearings did. Not even when placed behind a T5 killing 400. Don't get me wrong, I don't doubt that 75w90 would also work just fine. My bud's got an '88 Fox with a WC T5, it's got 200,000 miles on it, I had the trans out/apart about 3 years ago to replace some of the shifting rail parts. Bearings were not dusty at all, and I put it back together with only the shifting pieces, replaced. He had it at the drag track this past Friday night. IDK...the ATF hate seems like it's a bit overplayed.
87-up Frod used the 2nd design T-5. Totally different transmission. Tapered rollers w preload, composition frictions on the blocker rings. Those are SUPPOSED TO use ATF. Unlike the 1st design which has straight rollers IDENTICAL IN EVERY WAY to 10-bolt rear axle bearings - same part # - and BRASS blocker rings.
Use ATF in the 2nd design. (88-up in our cars) Use gear lube in the 1st design. (87-back) Yes, ATF will "work" in the 1st design, at least for awhile; but isn't "right" or "optimum".
87-up Frod used the 2nd design T-5. Totally different transmission. Tapered rollers w preload, composition frictions on the blocker rings. Those are SUPPOSED TO use ATF. Unlike the 1st design which has straight rollers IDENTICAL IN EVERY WAY to 10-bolt rear axle bearings - same part # - and BRASS blocker rings.
Use ATF in the 2nd design. (88-up in our cars) Use gear lube in the 1st design. (87-back) Yes, ATF will "work" in the 1st design, at least for awhile; but isn't "right" or "optimum".
Oh! O.K. So totally different trans. Not quite, but you're right about the counter shaft bearing. However, it doesn't really matter; I also said this:
Originally Posted by Tom400CFI
My counter shaft bearings never "ground to dust" using the recommended ATF. None of the bearings did. Not even when placed behind a T5 killing 400.
Like many veterans on this forum, I have plenty of other T5 experiences that lasted into the 150k miles realm that I failed to mention to avoid boredom & repetition, but the point is, there is no problem with ATF in any T5, just like there is also (probably) no problem with gear oil in that gen T5 either -even though it's a "home brewed" solution to a problem that doesn't exist. I've seen a plethora of T5 failures, I haven't seen counter shaft bearings "grind to powder" yet. Be it in a Mustang, F-bod, Jeep, S-10, Nissan...haven't seen it.
It could be stated (and I've read, in a T5 rebuilding how-to article), that gear oil is "too thick" for the tolerances in the tapered roller bearings on the main shaft, which IIRC are 0.000", +/- 0.0002? It's been ~30 years since I had to reference that spec so it might be wrong, but it's essentially "0", no clearance. The article claimed that ATF was necessary as it's thinner and would get to and lube those tight tolerances where gear oil would not. Do I believe that? Not really. Even though there is documentation there, saying that gear oil could actually hurt the main shaft bearings, I agree with you and feel that it'd work fine. Gear oil will work fine. ATF will work fine. "Synchromesh" will work fine. It doesn't matter. They're ALL, better than good enough if you change 'em when you should (which no one does). A well maintained, NOT-beat-on T5 will cruise right on by 200,000 miles w/no issues with any recommended lube, w/no dusty or powdered bearings.
I'd wager that the counter shaft bearing grinding to dust is about as prevalent as 305 3rd gens "pole-vaulting" themselves with steel drive shafts, but I haven't researched the actual stats on either.
Last edited by Tom 400 CFI; 04-25-2024 at 09:13 AM.
The 1st design T-5 DOESN'T HAVE that. The mainshaft bearing is a single-row ball bearing with NO preload. The bearing between the clutch gear and the mainshaft is about 7 loose STRAIGHT rollers with no cage. The rear is supported by the drive shaft yoke bushing like most other transmissions. There ARE NO tapered rollers on the 1st design T-5 mainshaft.
Many of the 1st design T-5s I tore up, first with the original L69 and later with a 400, had failed countershaft bearings. Since those run directly on the gear (the gear IS the inner race, just like C-clip axles, in fact the rear countergear bearing is THE SAME PART NUMBER as the 7½" and 8.2" axle bearing), that also trashed the gear. Which made the whole circle-the-drain positive feedback situation concerning the front of the case, EVEN WORSE. Anything that contributes to misalignment between the clutch gear and countergear will kill the T-5, including wear on the bearings.
The 1st design T-5 is a 60s / 70s design. Very much like a Muncie or T-10 except MUCH smaller in many critical areas. The 2nd design in MUCH more modern, with preloaded tapered rollers throughout, except for that one spot at the tip of the mainshaft, where it still has straight rollers (although as an assembly with a cage, not just loose rollers you load in by hand and stick in place with grease the way the 1st design is) and a Torrington to manage the end-preload.
The 1st design T-5 has BRASS blocker rings, just like a 60s / 70s manual transmission. The 2nd design has COMPOSITION rings, that look exactly like a GM smoothie automatic transmission clutch. This is yet another significant difference between them.
For all of these reasons, the 1st design T-5 works best with gear lube, while the 2nd design requires ATF or Synchromesh. Yes, ATF "works" in a 1st design; better than running it dry (although if the front countergear bearing is loose in the case, ATF leeeeeeks out MUCH faster than gear lube). But it is NOT optimum, and NOT correct; and GM's stuuupid instructions remain utterly meaningless, especially as they changed them from year to year WITHOUT ANY CHANGE WHATSOEVER to the actual PARTS inside the transmission.
Back in the 70s and 80s when my late little bro and I had a lively business rebuilding Muncies and T-10s, we used half STP and half ATF in those sometimes, which made them shift REAL slick but also leeeeked kind of alot. T-10s in particular, which usually have a much "stiffer" feeling than a Muncie, seemed to benefit from that. I never tried it in any 1st design T-5 though, because the synchros were already so large in comparison to the other parts, that they didn't need to shift any slicker than they did with gear lube.
It sure does. I've set 'em up. It has that....on the MAIN shaft.
Not sure what you're "arguing" here, or why you're getting worked up about it. Both recommended lubes will work fine, if changed. People don't change trans oil...and then they have problems. People beat on the trans, and then they have problems, no matter WHAT oil you put in 'em.
:thumbs:
You are correct: I'm sorry. I effffed up, was thinking about old 4-speeds too much maybe. The mainshaft bearing IS in fact a tapered roller.
The basic premise remains however. The 1st design T-5 is largely a 60s / 70s piece; with BRASS blocker rings and STRAIGHT ROLLERS on the countergear like a Muncie or T-10, it needs gear lube, as GM themselves passed on the info from Doug Nash in its earlier years, before the CAFE g00bz won the "annual retreat" argument and, contrary to Doug Nash's specs, called out for ATF. All this of course before Synchromesh even EXISTED.
Use gear lube in your 1st design T-5. It's ... just ... ALTOGETHER better suited to the parts it's built out of. Yes, ATF "works". Yes, Synchromesh "works". NO, it isn't the "right" thing for the parts the transmission is built out of. Most especially if your case already has any of the distortion across the front that allows fluid to leeeeeek out.
I'm "arguing" this because it's the TRUTH. The PARTS dictate the proper lube, NOT the "manual". Having dealt with 1st design T-5s since they appeared, and of course 4-speeds for MANY years before that, it's not too hard to penetrate the BULLSPIT that GM put out in the latter years of the 1st design T-5, where they REALLY wanted vehicles equipped with it to get a tenth or 2 better MPG. The CAFE people eventually prevailed, against the better judgment of the engineers and the warranty people, in spite of the thinner fluid being less than ideal. The FACTS remain though: the PARTS that the 1st design T-5 is built out of, are more suitably lubed with gear lube, than ATF. PARTS. PARTS. PARTS. PARTS. PARTS. PARTS. Those are the things that matter, not blabbermouth from non-technical "managers" without actual physical experience.
I had atf in my 83 t5 behind a zz4 since 2001. It never blew up but is was cognizant of its limitations. I found the fix for the atf/gear fluid conundrum was a t56 swap. All problems were solved!
You guys get it all out of your system yet?
Countershaft bearing / race / case failure will happen and does happen because constant vibration and force from two shafts pushing apart is greatest at that frontal headset gear location, and because aluminum stands microforces over tens of thousands of miles until it is worn by the race. Expanded shaft distance relationships harms proper gear tooth pattern and even if that doesn't hurt things directly, then
Neither Dexron nor gear oil helps nor hurts an aluminum casting from expanding the bore up front from vibration wear. A frontal steel case probably would have let the T5 last longer.
But "If only this had been used, then . . . " can go on and on when you know design A on a totally different unit worked and design B sucked on another. There is only one design update I would like T5s to have on all replacement parts across the board (besides a repaired case or new G-Force case) and really, it should have been done in 199x instead of machined into rebuilds piece by piece, sadly.
Wide width gears are no replacement for reliable lubrication. Friction material upgrades are no replacement for a well-driven, well-releasing clutch. Heavier oil seldom improves a true design flaw.
Said it before...T5's fail from neglect and abuse. I did what firechicken did...way back in '93.
Originally Posted by sofakingdom
it's not too hard to penetrate the BULLSPIT that GM put out in the latter years of the 1st design T-5, where they REALLY wanted vehicles equipped with it to get a tenth or 2 better MPG. The CAFE people eventually prevailed, against the better judgment of the engineers and the warranty people, in spite of the thinner fluid being less than ideal. The FACTS remain though: the PARTS that the 1st design T-5 is built out of, are more suitably lubed with gear lube, than ATF. PARTS. PARTS. PARTS. PARTS. PARTS. PARTS. Those are the things that matter, not blabbermouth from non-technical "managers" without actual physical experience.
I dug way deeper into this more than any average guy should but since I'm mlt1 certified for my job, I couldn't let it be. From the conclusion I came up with, verified by a gm power train engineer on another board, a chemist on a lubrication site, and Paul cangialosi all suggested synchromesh fluid. Paul recommended pennzoil. If you want to split hairs valvoline synchromesh is a slightly better choice. Dex3 supposedly doesn't have the same viscosity as the original dex2. Is dex 3 a bad choice? I can't really say. Maybe with shorter change intervals it would be fine. I can agree with the above statement that at the time bean counters pushed to use dex2 since it was cheaper and knew it would more than likely last until warranty was over. Knowing the third gen camaro was rushed into production this wouldn't surprise me.
My car had some sort of transmission fluid in it. It shifted fine. I did change it out to the valvoline synchromesh. I plan on doing some driving in the car in cooler weather. I'll report back any differences or quality if shifts.
Because the HO engine came out in mid 1983, long after the 83 owner's manual was probably published, a loose page with updates for the HO and 5-speed was in my manual, and it called for ATF.
My 1987 5-speed also had AFT. A shop changed it to gear oil in the early 90s, assuming ATF must've been an error. I told him the ATF was from the factory and asked him to change it back, but he recommended not. I think he did change it back, but I don't remember. His guess for why GM spec'd ATF was that it might provide easier shifting in cold climates.
A few years later after a smog test (at a different shop), someone tried to check the transmission fluid, thinking the 5th/reverse bolt was the fill bolt: "we couldn't get the fill bolt out, so we gave up." Then after not being able to shift into reverse to back out (or 5th), followed by showing me what they did and a "friendly discussion," they sent me to an associate's transmission shop, and he put it back together.
Topical tidbit: there's a 5W-30 tag on my transmission. And in the 1987 Service Manual for 5-speed lubricants, 5W-30 motor oil is one of a variety of specified lubricants, based upon RPOs.
No idea what's in my T5 today. Might've gone from ATF (from the factory), to gear oil (at the first shop), to 5W-30 (at the other shop); hasn't been checked/changed since, but still shifts fine after 37 years.
From the conclusion I came up with, verified by a gm power train engineer on another board, a chemist on a lubrication site, and Paul cangialosi all suggested synchromesh fluid. Paul recommended pennzoil.
On the 3si site (I know it's a different transmission, but the results are relevant), they got WAY into this, since their trans' are weak and fail synchros easily. Anyway, one guy invested a BUNCH of time, did oil changes and sampling, and he reported the results of various oils in a manual trans. In this testing, "Synchromesh" branded trans oils created better/easier shifting in those transmissions, but oil samples showed significantly more metal/wear. Detrimental? Probably not b/c many people use "synchromesh" w/o trans failure. In this test, the various gear oils used varied in results, but all showed meaningfully less wear and metals than "Synchromesh" branded products....but shifted harder. I can't remember if ATF was tested and sampled, but MY take away was to avoid "Synchromesh" fluid on a trans that shifts good (like the T5) and you want it to last.
This makes sense (to me); an oil that fends off friction and metal wear, it would seem would hurt syncho effectiveness; if it has EP additives to prevent tooth to tooth contact and wear, wouldn't it also do the same thing between the synchro surfaces? IDK for sure but seems likely and anecdotally, it appeared to work that way (harder shifting).
The biggest take away, however, was how quickly the viscosity degraded on ALL oil, in a gear box. Some lubes lost viscosity much faster than others, but they ALL lost significant viscosity, (in less than 15k miles)....some products, a LOT less. That was a surprise to me, since factory change intervals are way, WAY past the point that we learned the oil is basically already wasted. So, the lesson learned from that is you gotta change the trans oil. No one does, but you should. What oil you use doesn't matter that much. Use what you "fancy"....and change it.
Last edited by Tom 400 CFI; 04-29-2024 at 09:50 PM.
04-24-2024, 08:33 PM
Said it before...T5's fail from neglect and abuse. I did what firechicken did...way back in '93.
