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Rebuilt manual trans, used fresh oil, replace after break-in period?

XC92

Proven Member
1,189
216
Jul 22, 2020
Queens, New_York
As everyone here knows I recently rebuilt the manual trans on my '92 Talon TSi AWD. It was actually a '94 AWD trans as the dealer swapped it out back then due to some issues I vaguely recall with shifting into 2nd or 3rd. I rebuilt it because it kept popping out of 1st and was sometimes grinding on other gears.

Pretty sure that this was caused by incomplete clutch disengagement, given how worn the 1st-2nd sleeve teeth & synchros were, that in turn was likely caused by the infamous 1G clutch pedal slop issue that I've temporarily resolved and am about to permanently fix.

The rebuild itself has worked out great.

Anyway, I'm wondering if, when and with what to replace the initial gear oil after a certain break-in period, and if I should limit certain kinds of driving during this period, e.g. high revs, launches, excessive speeds, etc.--which I've been doing, for this and other reasons (need to replace TB so I'm taking it easy).

I put in mostly Mitsubishi GL-4 75W-85 gear oil, as per Jack's and others' rec. I know that some people rec other kinds of oil and respect that, it's just what I decided to go with.

And I say mostly because when I added the oil after reinstalling the trans, I stupidly did so before reinstalling the CV axles, and oil poured out the front diff openings until I was able to reinstall the axles and stop the leaks.

Enough leaked out that I didn't have enough of the Mitsu oil left to fully top things off, so I had to use some RedLine 75W-85 that I bought to put in the t-case to top it off. Hopefully that wasn't a bad idea as I understand that you're not supposed to mix oils, and thankfully there was still enough of the RedLine left to top off the t-case.

Anyway, that was several hundred miles ago, and I'm wondering if and when it'll be time to replace this oil, this time with a single source oil so no mixing.

And is it ok to stick with the Mitsu, or perhaps switch to the RedLine, both being 75W-85 (especially with colder weather coming)? My setup is stock and likely to remain so, so it's putting out stock power, and I don't race or do anything "crazy" with the car.
 

XC92

Proven Member
1,189
216
Jul 22, 2020
Queens, New_York
So when rebuilders recommend a break-in, it's generally for different kinds of rebuilds, higher HP output or different intended use? I seem to recall at least one of the better-known rebuilders recommending it. Not naming names as I'm not sure which.

Also, it's common knowledge (as I understand it) that the stock 1G AWD trans is not exactly the strongest part of a DSM. We all know this one way or another, e.g. notchy shifting, occasional blocking, can't handle more than modest HP boosts, etc.

But the caveat I keep coming across is "unless they're rebuilt". But rebuilt how? With better shimming? Shot-peened gears? Redesigned and better bearings, synchros, double springs, etc.? Using better oil? And does any or all of that get the trans to where it's comparable to the best manual awd trans, at least for this car segment?

Just curious as I did some of these things in my rebuild but certainly not all.
 
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1990TSIAWDTALON

Moderator
8,441
4,335
Nov 14, 2013
Independence, Kansas
Jacks never mentioned any breakin period for their transmission I bought years ago and it works fine. I have rebuilt a LOT of manual trannys (no DSM's though) and I never changed any "breakin" oil out of them. They ran 75-90 gear oil and were fine. Muncie, Borg Warner and Saginaw all just got rebuilt and put into use.
 

XC92

Proven Member
1,189
216
Jul 22, 2020
Queens, New_York
Jacks never mentioned any breakin period for their transmission I bought years ago and it works fine. I have rebuilt a LOT of manual trannys (no DSM's though) and I never changed any "breakin" oil out of them. They ran 75-90 gear oil and were fine. Muncie, Borg Warner and Saginaw all just got rebuilt and put into use.
Ok my mistake (again, memory's just not what it used to be, IIRC). It was Tim, not Jack. Different rebuilder, obviously also very reputable.

And this is where I came across the advice to replace the oil on a rebuilt trans:


There's also a link to a TRE article on breaking in a rebuild, but the link is dead. So I wasn't just imagining things.

Btw, lots of advice to use 75W90 but the FSM says 75W85. Which do folks who run more or less stock (or no more than 250-300HP) setups here use?
 

1990TSIAWDTALON

Moderator
8,441
4,335
Nov 14, 2013
Independence, Kansas
I run Mitsubishi Diaqueen from Jacks in mine. I have used Pennzoil Syncromesh before and didn't notice anything unusual.
 

XC92

Proven Member
1,189
216
Jul 22, 2020
Queens, New_York
I run Mitsubishi Diaqueen from Jacks in mine. I have used Pennzoil Syncromesh before and didn't notice anything unusual.
Don't some rebuilders say that you shouldn't use Synchromesh in a trans, because they could harm the synchros or gears? Same for Shockproof?
 

1990TSIAWDTALON

Moderator
8,441
4,335
Nov 14, 2013
Independence, Kansas
IDK, it hasn't ever hurt mine. Some gear oils have some parifin in it and I have heard to stay away from it but the Pennzoil stuff really worked good and if I noticed anything, it shifted just a tad smoother.
 

BLACK'98DSM

Proven Member
3,122
1,056
Feb 9, 2019
Alabama
The only reason I change the fluid in a trans when it's still new is to remove any contaminates or debris that my have gotten inside the trans during reassembly, or possibly left behind when I cleaned it. I rarely notice anything in the fluid. But when I do, it makes me glad as hell I changed it. It's more of a precautionary procedure, not required. But I always chose to do it.
 

XC92

Proven Member
1,189
216
Jul 22, 2020
Queens, New_York
I want to know why diaqueen is so expensive. I run amsoil and I have no problems
I think I paid $13.50 a qt, but I've seen them for $12, even cheaper from Japan. Is that considered to be expensive? RedLine qts are around $20.

The only reason I change the fluid in a trans when it's still new is to remove any contaminates or debris that my have gotten inside the trans during reassembly, or possibly left behind when I cleaned it. I rarely notice anything in the fluid. But when I do, it makes me glad as hell I changed it. It's more of a precautionary procedure, not required. But I always chose to do it.
I'll probably replace mine for these reasons. I haven't heard or felt any grinding and was very careful to keep things clean and debris out when I rebuilt it, but I did all the work outside and who know what might have blown in when I wasn't looking. Plus I'm curious to see what color the oil is and if there's any metal dust in it or sticking to the plug magnet I added. Too bad the trans magnet can't be removed without taking the whole thing apart. It should be a bolt-in part for routine servicing. I'll probably replace the fluid around 1000 miles, or I might wait still spring. I want to start actually enjoying the car again.

IDK, it hasn't ever hurt mine. Some gear oils have some parifin in it and I have heard to stay away from it but the Pennzoil stuff really worked good and if I noticed anything, it shifted just a tad smoother.
There's so much conflicting advice out there about such things that I wish someone just did an actual real-world test on them and posted the results, the way that UL (which I worked for in college and have done IT QA in the past) does. They'd have to risk destroying some parts but I'd think that Penzoil or automakers could afford it. What we get most often is anecdotal experience that doesn't control for various factors beyond using fluid X with part Y, e.g. driving style, engine HP, where driven, etc.
 

RWD4G63

Proven Member
460
113
Dec 7, 2011
Paw Paw, Michigan
There's so much conflicting advice out there about such things that I wish someone just did an actual real-world test on them and posted the results, the way that UL (which I worked for in college and have done IT QA in the past) does. They'd have to risk destroying some parts but I'd think that Penzoil or automakers could afford it. What we get most often is anecdotal experience that doesn't control for various factors beyond using fluid X with part Y, e.g. driving style, engine HP, where driven, etc.
There are white papers on this. Also, if you do some reading, you can figure out that a lot of companies use cheap base oils and very general additive packages, especially in gear oil. Plenty of oils out there superior to Diaqueen, but you'll have to get past the dogma of "It's all I've used and I've never had a problem" and "X is the best" people. Amsoil, Redline, Motul, and HPL are all top of the line brands I would recommend.

Pretty sure John @Tre recommends changing the oil after a few hundred miles on his rebuilds IIRC.
 

XC92

Proven Member
1,189
216
Jul 22, 2020
Queens, New_York
There are white papers on this. Also, if you do some reading, you can figure out that a lot of companies use cheap base oils and very general additive packages, especially in gear oil. Plenty of oils out there superior to Diaqueen, but you'll have to get past the dogma of "It's all I've used and I've never had a problem" and "X is the best" people. Amsoil, Redline, Motul, and HPL are all top of the line brands I would recommend.

Pretty sure John @Tre recommends changing the oil after a few hundred miles on his rebuilds IIRC.
Thanks, that's what I was asking. For stock situations with zero racing, launching, etc., and only moderately aggressive driving like in mine, it probably doesn't matter as much, but I'd still like to know a bit more about this.

Best to keep it out of here though, given the arguments such topics tend to spawn. So I'll do some research and reading and reach my own conclusions. Same as with other "controversial" topics like BSE and motor oil.

Most likely I'll get RedLine if I decide to use something other than OEM, as that seems to be the most widely used alternative oil with DSMs. And then it appears that MT-85 is my best bet. Cold winters, hot summers, stock power, no racing.
 
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twicks69

Supporting Vendor
3,902
1,039
Mar 12, 2004
Milwaukee, Wisconsin
You only replaced bearings and synchros, no gears. There should be next to zero debris in the transmission, especially since you had it apart and fully cleaned it. Throw a neodymium magnet on the drain plug.

Your gear oil should be fine.
 

XC92

Proven Member
1,189
216
Jul 22, 2020
Queens, New_York
I also replaced the 1st-2nd hub & sleeve, which has dog teeth, and I dressed the 1st, 3rd, 5th & rev gears. 1st & rev because the teeth were somewhat rounded due to wear and tear, and 3rd & 5th because there were chipped teeth at the "corners" due to rebuilder (i.e. me) error when taking the stacks apart.

So I figured some of that is going to come off during initial use, despite hearing and feeling no grinding whatsoever so far. I put a neo magnet on the drain plug before I put everything back together, so if anything did come off, it probably captured some of it, the rest hopefully by the main magnet, also replaced with a neo.

There was also initially a very small leak on the bottom of the trans case after I drove it a bit, that I suspect was coming from the clutch housing to trans case seal since there was no oil on the front or rear of the case, from the fill plug, from either axle seal, or the bell housing. I wiped it off and it reappeared after some more driving, but after 2-3 of thse cycles it appeared to have gone away.

I thought that draining the oil might also give me an idea of whether the leak was bigger than I thought and I have to take things apart again to get a better seal. Is it normal for there to be tiny leaks after a rebuild, or is that a bad sign even if it appears to have gone away? No issues with the actual trans so far, other than the usual occasional notchiness typical of this trans.
 

twicks69

Supporting Vendor
3,902
1,039
Mar 12, 2004
Milwaukee, Wisconsin
There should be no leaks from the transmission case unless you didn't properly seal it.

Put a piece of cardboard under the car and see how much is actually seeping out, and from where.

If you really want to drain it for kicks, go for it. Either way, if it is leaking you likely didn't install a seal properly or didn't fully seal the transmission case properly.
 
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