Anatomy of a transmission failure....

takza · Post by **takza** » Sat Jul 09, 2005 7:26 am

My beloved Tercel 4WD transmision is toast.

It's demise started on a camping trip while driving offroad under fairly severe conditions.

I first noticed a problem when I heard a tick-tick-tick and some extra noise besides the typical gear whine...reflected off a dirt bank I was passing while crawling along a trail. Didn't think too much of it at first.

Problem is that it gradually got worse.

At first I thought it was lmited to EL and 1-2-3 gears...but later found that there was noise in all gears with the windows closed.

When the oil was drained after the trip back...I found...besides the usual larger steel chips caught on the drain plugs...very fine metal particles suspended in the gear oil.

My guess being this started with a failed ball bearing under heavy loads...where the ball surfaced spalled and lost some metal. This metal then gets carried thruout the trans-front diff...trashing everything it lubes...causing more metal to be ground from most surfaces.

Trans now makes noise in all gears...espec when warmed up.

Now have drained it and put in 4 qts of 20W50 motor oil...which I'll run real easy for 50 miles or so to cleanup the metal particles and then will put in 4 qts 85W140 gear oil along with some Militec additive.

After driving the car very easy for 50 miles or so...I drained the oil and found very fine metal particles in it, but not a lot. Also a small amount of larger stuff on the magnets again...so something is still "chunking" away.

Put the 85W140 oil in...along with 7 oz Militec. The car drives OK...not real noisy until the trans warms up good...still not as noisy as with the 20W50...so heavy oil helps.

Have seen Militec "cure" a couple of failed bearings before...though I haven't used it with a major failure like this. Worth a try I guess.

Militec won't replace lost metal...but tends to toughen the metal surface....might make it last longer.

Other wise...it's a complete trans-diff changeout...have a good trans, but not the diff....too dumb to take out the diff with the trans I guess.

Car is now relegated to local putt-putt duty.

takza · Post by **takza** » Tue May 08, 2007 5:52 am

I'm thinking that checking the condition of the drained gear oil (when changing it) is something that needs to be done every time the oil is changed out.

The condition of the oil and the amount of metal on the 2 magnetized drain plugs can tell you a lot about what is going on inside amongst all that whirring metal.

How to do forensics on drained gear oil?

* make sure the pan you will be draining into is CLEAN...you want to be able to see any metal chunks or fines left in the pan.

You'd want the car level and up on jacks when draining it...with a filler plug out and the oil hot if possible to have it drain fast and carry out most particles.

* chunks will probably be from too aggressive shifting....these are the tips of the gears. Shame on you....

* after draining the oil from all 3 drain plugs...it's best to let the oil sit in the pan for around 1/2 hour to let the bubbles and so forth dissipate.

* to check for metal "fines"...you should place the pan in the sun and using your finger...run it thru the oil just on the surface. If the old oil looks something like metallic paint before it's sprayed...YOU'VE GOT A PROBLEM.

* also need to check what metal is on the 2 plugs with the magnets in the ends. The metal is magnetized...so it's difficult to tell how fine it is. I run a clean fingertip over the end to see if any of it is larger particles.

Deciding what you've got:

* as far as I know...large chunks (1/8" or less) means you or someone has been or is shifting like an idiot. Not much to do except drive it and hope for the best?

* the "fines" probably mean a bearing is self destructing and your trans is failing. You can have this and see no other symptoms when driving the car. My *guess* would be the next gear and shaft down from the input shaft.

About the only thing you might do is to change the gear oil every 5-10K and/or try an additive such as moly or militec. But I'd have to say that THE END IS NEAR.

Listen for increased trans noise over time...when it gets noisy you'll know it...it's not the typical gear whine in first and second and so forth...it's loose and noisy bearings?

You will notice trans noise most when driving slowly past a wall or building...the sounds are reflected by the wall thru an open window.

* right click to see inside the 2WD transmission:

takza · Post by **takza** » Wed Oct 31, 2007 4:53 am

second trans:

Drained about 1/4 cup trans oil and checked it for fines after 3K on new oil and moly additive. Despite the moly making it darker...could not find any floating metal. Either the moly has stopped any destructo stuff....or the previous 6K drain where I found "fines"was just cleaning the floating stuff off the surfaces inside.

Looks like we in bidnuss....

Post by **Petros** » Wed Oct 31, 2007 8:45 pm

It is a little late now, but if you had used some sort or solvent in the trans it would have clean the metal flakes out sooner. I have heard a 50/50 mixture of ATF and gear oil (cheap stuff) run until warm and then drained will clean all of the fine particles out of the trans. I would have also flushed out the case (with all of the plugs removed) with a lot of solvent just to get as much of the metal out of the bottom during the oil change. It would not have fixed anything broken, but it would keep the metal particles from doing any more damage.

Keep us posted on how log it lasts. Usually at this stage most will fill the trans with saw dust and sell it. I also heard banana peels work pretty good too.

takza · Post by **takza** » Thu Nov 01, 2007 2:51 am

This is a second trans. Approx time line:

* trans fails on trip...starts making bearing noises...makes it back 2K miles...so much metal in the oil that all parts of trans make noise...difficult to get in/out 4WD..can hear actual grinding on diff gears in 1st under load. Otherwise...trans acts OK.

* refill with 1 gallon 20W50 motor oil..run 50 miles...fines found

* refill with 1 gallon 85w140 gear oil plus Militec...run 1-2K miles...some fines still found

* install second trans...fill with the same 1 gallon heavy gear oil plus Militec..run 500 miles or so...to get Militec treatment...not an espec good move?

* refill with 3 qts 80W90 plus 1 qt additive...run 6K miles...some fines still found...thinking new trans is toast...but no noise or symptoms

* refill with 1 gallon 80w90 and moly additive..run 3K...no fines found in 1/4 cup drained oil

So it looks like an intermediate full flush is needed to get the fines out...if the destructo process is not still happening? Not just change it out one time. Did not know whether diff was failing or not.

Still running the original front diff that has had the fines run thru it...no issues so far.

"fines" = very small floating metal particles presumed to be from failing bearing...these do not drop out of suspension...seen in full sunlight in drained oil after it sits a while.

Conclusions? IF a trans is noisy and is putting "fines" into the oil...it isn't going to get any better. You need to run SOMETHING in the new trans to flush it (for less than 6K for sure) AFTER new trans in...to clean it out...not just drain and refill.