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Best manual tranny fluid

27K views 26 replies 16 participants last post by  Splicer  
#1 ·
I was looking at getting some Red Line MT-90 for my X-Runner's tranny but ran across some Royal Purple Synchromax. Anyone have any experience with either or recommend one over the other?

Thanks!

J.
 
#5 ·
I was looking at getting some Red Line MT-90 for my X-Runner's tranny but ran across some Royal Purple Synchromax. Anyone have any experience with either or recommend one over the other?

Thanks!

J.
Do not put the mt-90 in your tranny, unless you like the smell of gear oil. I put it in and I would constantly smell gear oil. I think it was coming out of the breather and getting into the cab, because it was not leaking. Get the redline MTL, if your going to change it.
 
#7 · (Edited)
(to jboogie)

if you run straight redline mtl, you MAY experience problems. it is too thin for the specs on your manual tranny. mt -90 would be the choice as far as viscosity is concerned. it is a 90 wt lube .(or you could try a blend of the two, but read up on that in detail first)
your manual tranny calls for a 75-90 wt lube .(but you probably knew that) :)
(to scott aw)
I have tried conventional gear oil, redline and amsoil. I have had the best luck with redline so far, it has improved shift quality in all seasons. but for me it looks like nothing will totally fix the clunky notchy shifting i experience, more so in cold weather.
good luck and hope either one you choose works for you.
 
#8 ·
I will change mine soon and I plan on using M1 75W-90 synthetic.
 
#9 ·
I put 75w-90 Quaker state full syn in at 20K a over a year ago. Its only slightly more than the convential stuff, and not overpriced like the others.

Wanted better flow/protection when well below zero. Not much noticeable diff most times, she has shifted like butter for over 3 years anyway. Changing all fluids to full syn (except LSD) my winter mileage became slightly better.
 
#10 ·
I put 75w-90 Quaker state full syn in at 20K a over a year ago. Its only slightly more than the convential stuff, and not overpriced like the others.

Wanted better flow/protection when well below zero. Not much noticeable diff most times, she has shifted like butter for over 3 years anyway. Changing all fluids to full syn (except LSD) my winter mileage became slightly better.
Demoncleaner, what did you use for the rest? 75W-90 all around?
 
#12 ·
some great info in here.

Since my transmission blew its reverse gear at 17k miles, I've noticed that the warranty replacement has been VERY stiff when cold. I live in Texas, so cold == above freezing. :)

Once the trans warms up, it shifts smooth and easy, but until then 1st and 2nd are damn near impossible to select.

I would expect this from a brand new transmission, but I've put about 1400 miles on it since it was replaced, and it still does this.

It actually snowed (real snow, not sleet) last night, and this morning it was damn near impossible to get into gear after backing out of the driveway.

It's so tight that if I'm sitting on flat, start the engine w/ the parking brake released, leave the trans in neutral and release the clutch, the vehicle starts crawling forward and a noticeable drag is placed on the engine... that lasts about the first 6-8 seconds the truck is running, and then there's a noticeable "release" if I push the clutch in for another minute or so. After I can get it in gear and get going, it will finally slot 1st and 2nd with no issue after about 3 miles of driving.

As such, I figure it's probably wearing down some tight parts and putting lots of metal in the oil, so I will likely change the fluid in another 1000 miles or so...

I'm a big fan of RedLine, (I run it in just about everything, though I use Mobil 1 in the Taco engine because I can find it in gallon jugs easier than I can find RL in quarts) so I'd probably want to dig up some RedLine synth for the transmission.
 
#13 ·
Bought my '07 one year ago. Trans shifted fine not notchy at all except for the non-syncro'ed first.
Last Nov changed fluids to synthetic. Went with Redline MT-90 in the transmission (and 75w90 NS in all the rest). Thought this would be good for the cold winters here in MN.
Not sure I'd do the MT-90 again. Don't feel the shifting is as smooth as it was with the OEM fluid in all gears. May try another synthetic this summer. Only 10k on the truck but it should be broke in fine.
Did the exact same change in fluids to Son's 99 (95k on it) and he feels the same way. Shifted smoother with the OEM non-synthetic fluid.
I know a lot of people like the RL but we'd not do the MT-90 again.........For what's it's worth from MN.
 
#14 ·
Hopefully I can clear a few things up here...

I was looking at getting some Red Line MT-90 for my X-Runner's tranny but ran across some Royal Purple Synchromax.
Synchromax is for transmissions that use a light weight oil. It is essentialy the viscosity of ATF, very thin. You should not use this in a transmission calling for 75W-90 gear oil.

Do not put the mt-90 in your tranny, unless you like the smell of gear oil. I put it in and I would constantly smell gear oil. I think it was coming out of the breather and getting into the cab, because it was not leaking. Get the redline MTL, if your going to change it.
Redline MTL is gear oil, same as MT-90. It is a thinner 70W-80 GL-4 fluid. MT-90 is 75W-90 GL-4. If you were smelling gear oil with MT-90 and not MTL, then it must have been overfilled at one point.

Quote:
Originally Posted by sechsgang
Demoncleaner, what did you use for the rest? 75W-90 all around?

Yep, same stuff in tranny, transfer, & front diff.
Normal 75W-90 gear oil can be used in the tranny (as manual allows GL-5), but with the LSD additives usually included in off-the-shelf gear oils, it is usually too slippery for optimum shifting.

Since my transmission blew its reverse gear at 17k miles, I've noticed that the warranty replacement has been VERY stiff when cold. I live in Texas, so cold == above freezing. :)

Once the trans warms up, it shifts smooth and easy, but until then 1st and 2nd are damn near impossible to select.

I would expect this from a brand new transmission, but I've put about 1400 miles on it since it was replaced, and it still does this.
I had the same problem with a new manual trans replaced by the dealer. The problem was, the dealer filled the replacement tranny with bulk 80W-90 gear oil (I asked). As soon as I put MT-90 in, cold shifting was back to normal.

Hope this helps.
 
#15 ·
Normal 75W-90 gear oil can be used in the tranny (as manual allows GL-5), but with the LSD additives usually included in off-the-shelf gear oils, it is usually too slippery for optimum shifting.
So what would you suggest instead? 75W-140 maybe? It's thicker, so probably not as "slippery"?
 
#16 · (Edited)
So what would you suggest instead? 75W-140 maybe? It's thicker, so probably not as "slippery"?
Sorry, what I meant was that most off the shelf gear oils are designed for differentials. They are GL-5 (extreme pressure rated) with limited slip additive usually already included. The limited slip additive makes the oil more slippery so that the diff carrier clutches operate smoothly and don't chatter. What this means is that in your transmission, the synchronizers will have additional slippage, and shifting will be difficult or notchy. 75W-140 is a gear oil meant for differentials under extended high loads, and is too thick for a manual transmission.

There are some good GL-4 gear oils out there, specifically designed for manual transmissions. There are also some GL-5's without the limited slip additives that can be used in a manual transmission. Look at Redline oil and Amsoil products for more information.

To sum it all up, there is more to gear oil than just the weight. Before replacing fluids, you should try to understand and meet the requirements so that the life of your vehicle is extended and not reduced.
 
#21 · (Edited)
Gone, why do you say that? The only difference I can see is that one is GL-4, the other is GL-5. What makes the GL-4 a better choice? Just trying to learn here, thanks for your input.

BTW, which one of the redlines do you think are best for:
1. Front diff (MT-90 or 75W90NS or ???)
2. Rear Diff offroad non-LSD (MT-90 or 75W90NS or ???)
3. Transfer Case (MT-90 or 75W90NS or ???)
Ring and pinion differentials (front and rear) ALWAYS need GL-5. The pressures exerted on the oil film between gear teeth are so great that special additives are needed to prevent metal to metal contact. A GL-4 fluid here will not protect parts. Front and rear diff should have a GL-5 fluid. Since you have a non LSD diff, you could use either a NS fluid, or a normal diff fluid with the LSD additive included. The LSD additive has the added benefit of increasing the viscosity of the oil at high temps and reduces sliding friction on gear teeth and is safe to use in a non-LSD.

Your owner's manual will state what fluid requirements are for your transmission. Mine says GL-4 or GL-5 is acceptable. Some (not all) transmissions are sensitive to GL-5 additives which may damage soft metal synchronizer parts. It's not that GL-4 is better for shifting, it's that most transmission specific gear oils are GL-4 rated for the above reason.

You should read the information available on both Redline and Amsoil websites. It will help you choose the best fluid for your application even if you don't use their products.

Check out http://www.bobistheoilguy.com/forums/ubbthreads.php as they have a gear lube forum. Lots of great information there.

I also just found this great bit on GL-5 lubricants.
http://www.eng-tips.com/viewthread.cfm?qid=120197&page=1
 
#22 ·
So ^^^ your saying us guys with manual tranny's "should" see greater results with a GL-4 tranny oil over the Gl-5 that is more thinker made for the pumkins. I'm kinda concerened with the syncro's becuase my truck shifts alright above 2K under 2K it's notchy a little, so the smoother the better. I've heard people like some oils and others don't like the same oil.. Almost seems you gotta play around and see what you/your truck likes the best.. I agree with you all, I'm putting mobil 1 syn 75w-90 in my axle and am not 100% sure what in the tranny yet.. I'll be changing at 12K, about another 150 miles.. SO I gotta make up my mine.. what are all my options listing from what you'd recomend at top. thanks..I beleive I can get some Amsol if that's recommended highly..
 
#23 · (Edited)
Whatever you choose, make sure it does not have the friction modifier in it (for the manual tranny). That's way more important than the brand you pick. I will go with Redline, eithe MT-90 of 75W90NS. The 75W90NS has the advantage that with this choice, all I need is one kind of oil that fits all: both diffs, transfer case & tranny. I'd buy that in the gallon size.
 
#24 ·
FYI, because of what i read in this thread, i went with amsoil manual transmission fluid (75w-90/GL4) and shifting is much better than stock now. maybe it had gl5 and it was too slippery and iikes the GL4 more.

thanks gonesurfing.