Grinding in third gear., Mainly when down shifting. Options

[TClifton91]

So I've been having a problem with third gear. When shifting through gears some times 3rd grinds when going from 2nd to 3rd. But when down shifting it grinds every time, 4th to 3rd. Anyone had this problem or know what it could be?


As always thanks for any help!


-T

[KAOS]

I had the same issue.

Most likely the syncro's are dying, seems to be common for the 3rd gear. You can try changing out your transaxle oil to see if that helps.

[TClifton91]

I had the same issue.

Most likely the syncro's are dying, seems to be common for the 3rd gear. You can try changing out your transaxle oil to see if that helps.

So is that something the average person could do or would you recommend taking it to a shop? Always been pretty good with my hands and figuring stuff out. But with this I wouldn't even know where to begin.

Thanks

[KAOS]

Its pretty straight forward. Check the stickies, they always have the most useful information.

http://www.6gc.net/forums/index.php?showtopic=37397

^^ its for changing the ATX (automatic) transaxle fluid, but the procedure for MTX is pretty much the same.

[Box]

It's a common occurrence with the Toyota S and C series transmissions. Long story short get 3 quarts of oil, 2 parts being 75W-90 GL-4(will have to get online probably) and 1 part being Pennzoil Synchromesh. Should help alleviate the issue if not cure it, just depends on how bad the synchronizer is.

This post has been edited by Box: Jul 16, 2014 - 2:49 PM

[Special_Edy]

I had the same issue.

Most likely the syncro's are dying, seems to be common for the 3rd gear. You can try changing out your transaxle oil to see if that helps.

So is that something the average person could do or would you recommend taking it to a shop? Always been pretty good with my hands and figuring stuff out. But with this I wouldn't even know where to begin.

Thanks

You need a rather large socket to remove the drain plug and fill plug, it may have been a 22mm on mine. First step is to remove the drain plug on the lower driverside of the transaxle, directly under the driverside cv axle shaft. Once you have drained all the fluid, you need to reinstall the drain plug, I dont know the torque spec off the top of my head but its fairly tight.
Remove the upper plug, it is on the front of the transmission, somewhat on the underside facing downwards at a slight angle. It is the same size as the drain plug. The ttransaxle will take exactly 2.7 quarts of 75-90W (I think 75-90) gear oil, but everyone suggests Pennzoil Synchromesh Fluid in this weight. The Pennzoil is known to fix third gear grinding in our transmissions. If the car is on a perfectly flat surface, 2.7 quarts will bring the fluid EXACTLY level with the drain plug hole, so that if you were to put 2.8 quarts for example, .1 quart would come spilling out.
This is all for the GT, I dont know about the ST 5spd

[TClifton91]

Thanks for all the great info guys . I will be tackling this over the weekend, will let you know how it goes and if it fixes the problem.

[Box]

This is the cheapest GL-4 I came across: http://www.summitracing.com/parts/bpo-023-7729/overview/ Worked well, added Synchromesh later and it helped even more. Two quarts of the Brad Penn with a quart of Synchromesh and you're good to go. If you really love your car supposedly the Motorcraft GL-4 is pretty much the best thing you can put into your gearbox, it's really popular with the Miata crowd. It's also three times the price of the above mentioned.

[VavAlephVav]

https://www.youtube.com/watch?v=aAWxZRuBXtw

there is some good demo videos on youtube of how a transmission works which will help you understand how the synchronizer works. the different(more expensive) gear oil will create more friction for the little drum to grab on to. and having somebody actually take it apart and replace stuff would be really pricey.
The little trick I use on mine basically uses the synchronizer from second gear to slow it down like this: say you're in 4th or 5th and you want to shift down to third. push in the clutch and then move the stick to the second gear spot but don't go all the way in you just need to hold it in that spot for a moment, and Then push it up into third and it won't crunch at all, now let out the clutch. Assuming you're not doing some kind of street racing where you'd need to shift down much quicker than that it really only takes a couple seconds to do. if you check out the vids of how the synchronizer works you'll understand better that we are just using the drum from second gear to slow the gear down so that it wont crunch in 3rd, most likely the drum/synchronizer for 3rd has been used hard so many times that it has worn away slightly and no longer grips like it should.
I run all 2.7 qts of Penzoil Synchronomesh in mine (the bottle says it was made for Chryslers), and other people have said they got even better results with Redline MT80 which is about $20 a quart. but I'm content enough with the results I've gotten from my little trick and don't feel the need to change the oil again. btw my drain and fill plugs were pretty rounded and I couldn't get them off with a regular 12 point so I went to Sears and got a 6 point box end for it, and I think I couldn't find the metric 22mm one but the 15/16" was the same size. then I went to Toyota and bought two new plugs. and you're going to need a little oil pump to refill it, you'll never be able to just tip the bottle up and pour it in to the fill hole.

This post has been edited by VavAlephVav: Jul 16, 2014 - 9:26 PM

[Box]

That or just rev match, take that synchronizers!

[ricochet1490]

a bunch of transmssions use full synchromesh. don't be scared of it as your only fluid. This the only thing in the nv3500 found in every manual s-10 dakota, silvarade and ram from the mid 90's through the mid 00's

[Box]

Those transmissions were also designed to run on Synchromesh, where as these were not. It's like saying, "Well a lot of Borg Warner transmissions in Fords used ATF, so I guess that's just dandy in anything else I deem fit." A lot of older Honda transmissions used straight up 5W-30 motor oil. What works for one doesn't work for all.

This post has been edited by Box: Jul 17, 2014 - 12:22 AM

[TClifton91]

https://www.youtube.com/watch?v=aAWxZRuBXtw

there is some good demo videos on youtube of how a transmission works which will help you understand how the synchronizer works. the different(more expensive) gear oil will create more friction for the little drum to grab on to. and having somebody actually take it apart and replace stuff would be really pricey.
The little trick I use on mine basically uses the synchronizer from second gear to slow it down like this: say you're in 4th or 5th and you want to shift down to third. push in the clutch and then move the stick to the second gear spot but don't go all the way in you just need to hold it in that spot for a moment, and Then push it up into third and it won't crunch at all, now let out the clutch. Assuming you're not doing some kind of street racing where you'd need to shift down much quicker than that it really only takes a couple seconds to do. if you check out the vids of how the synchronizer works you'll understand better that we are just using the drum from second gear to slow the gear down so that it wont crunch in 3rd, most likely the drum/synchronizer for 3rd has been used hard so many times that it has worn away slightly and no longer grips like it should.
I run all 2.7 qts of Penzoil Synchronomesh in mine (the bottle says it was made for Chryslers), and other people have said they got even better results with Redline MT80 which is about $20 a quart. but I'm content enough with the results I've gotten from my little trick and don't feel the need to change the oil again. btw my drain and fill plugs were pretty rounded and I couldn't get them off with a regular 12 point so I went to Sears and got a 6 point box end for it, and I think I couldn't find the metric 22mm one but the 15/16" was the same size. then I went to Toyota and bought two new plugs. and you're going to need a little oil pump to refill it, you'll never be able to just tip the bottle up and pour it in to the fill hole.

I tried this little trick, no grinding at all! I would have a little harder time rev matching seeing as how my tach is broken...both of them I think I'm going to try a nice blend of oils this weekend, partly synchromesh.

Thanks guys!

[SwissFerdi]

Those transmissions were also designed to run on Synchromesh, where as these were not. It's like saying, "Well a lot of Borg Warner transmissions in Fords used ATF, so I guess that's just dandy in anything else I deem fit." A lot of older Honda transmissions used straight up 5W-30 motor oil. What works for one doesn't work for all.

I've had SynchroMesh only for a year without issue.

[Tort1llaboy]

isent the synchronesh a temp sulution?

[TClifton91]

Ok so I got eyes on the drain and fill plug, I see what you mean about not being able to just pour the bottle in. At my work I found a gear lube pump for marine applications, wouldn't that kind of pump work just the same?

[KAOS]

I just used a long stemmed, flexible funnel to sit in the fill hole. Works great.

[TClifton91]

I just used a long stemmed, flexible funnel to sit in the fill hole. Works great.

Oh ok. So did you jack the car up or just feed the tube through the bay. I have gen 4 3sgte so my engine bay is unbelievably cluttered.

[VavAlephVav]

Any oil pump will do it, they sell cheap ones at the auto parts store for $10. I had it jacked up and then measured the 2.7 qts in since its not level.

[Special_Edy]

The trick to rpm matching is to force pop the shifter into neutral and then apply force to shift it into the next gear. Let off the throttle and allow the rpms to slowly drop. As soon as the rpm of the motor hits the speed of that gear, it will kick into the gear, without the clutch. Due to the shape of the gear teeth, it only works if the motor is loosing rpm, so if you downshift you have to first rev the engine in neutral and then apply shifter pressure as the rpms fall (since you are shifting to a lower gear with higher rpm).
Probably best to practice with 3rd to 4th or 4th to 5th until you get smooth at it, they are more forgiving than 3rd or 2nd. Like I said slowly drop the rpms, you dont want to totally lift your foot of the throttle.

Even if you are using the clutch you should still develop a feeling for the rpm matching. With the clutch I just know how LONG to lift my foot off the throttle and when to release the clutch pedal to hit the rpms perfectly.

I probably do half my shifts in the car without the clutch and 100% of my shifting on my motorcycle without the clutch, its much smoother.

This post has been edited by Special_Edy: Jul 17, 2014 - 11:56 AM