Synchros -any availability? potential fixes?

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My1985Tercel
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My tercel:: 1983 Tercel 4x4

Synchros -any availability? potential fixes?

Post by My1985Tercel »

I have an 83 that appears to have synchro issues, in the form of some grinding, particularly down-shifting into 2nd.

From what I've read here it seems that parts are simply not available. Is this basically a 'find one at the junkyard and cross your fingers' type of situation at this point?

I was thinking of trying to change out the gear oil (hasn't been done on my watch). I figure that it's easy enough. Any recommendations on a particular brand/weight? Has anyone ever 'cured' an issue doing this?

Thanks for any advice.
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dlb
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Re: Synchros -any availability? potential fixes?

Post by dlb »

There is no consensus on which gear oil is best. There is a long thread here about this very topic.

viewtopic.php?f=2&t=9667
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NWMO
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Re: Synchros -any availability? potential fixes?

Post by NWMO »

2985Tercel,

I’m on pages 4 and 5 of the linked discussion. So far, I have been very pleased with the Amsoil product I referenced.

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Petros
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Re: Synchros -any availability? potential fixes?

Post by Petros »

you might improve the function of your syncros with an AFT flush. put in 50/50 mix of ATF and cheap gear oil and drive it around for a few days, getting it up to hwy speed so it gets good and warm. than with it still warm, drain it out. ATF has a strong detergent action and will clean out gum and deposites that might be filling the small grooves on the face of the sycro. Some forum members have had good luck "restoring" syncro function with an AFT flush, but it does not always work if they are too far gone.

Than fill it with your final quality gear oil, make sure it gets to the fill line (upper plug in the left side of the front diff). Allow enough time for it to flow all the way back to the transfer case, complete filling can be very slow.

You might consider using 50/50 synthetic gear lub and conventional gear oil. the problem with synthetic oil is the trans was not designed to use it, so it will make the synros act like they are worn out (it is too slippery), and/or it can seep out all the oil seals. It is too slippery for our trans design. Usually just clean fresh conventional gear lube will make it shift better.

I am currently running 3 quarts of 85W-90 gear oil, and one quart of ATF. my syncros are worn too, and it seems to help them shift, particularly after a cold start on a cold day (below freezing), it would hardly shift into first or second gear before it warmed up.
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Re: Synchros -any availability? potential fixes?

Post by knot2shabby »

Petros wrote: Sun May 19, 2019 3:22 pm you might improve the function of your syncros with an AFT flush. put in 50/50 mix of ATF and cheap gear oil and drive it around for a few days, getting it up to hwy speed so it gets good and warm. than with it still warm, drain it out. ATF has a strong detergent action and will clean out gum and deposites that might be filling the small grooves on the face of the sycro. Some forum members have had good luck "restoring" syncro function with an AFT flush, but it does not always work if they are too far gone.

Than fill it with your final quality gear oil, make sure it gets to the fill line (upper plug in the left side of the front diff). Allow enough time for it to flow all the way back to the transfer case, complete filling can be very slow.

You might consider using 50/50 synthetic gear lub and conventional gear oil. the problem with synthetic oil is the trans was not designed to use it, so it will make the synros act like they are worn out (it is too slippery), and/or it can seep out all the oil seals. It is too slippery for our trans design. Usually just clean fresh conventional gear lube will make it shift better.

I am currently running 3 quarts of 85W-90 gear oil, and one quart of ATF. my syncros are worn too, and it seems to help them shift, particularly after a cold start on a cold day (below freezing), it would hardly shift into first or second gear before it warmed up.
Hi Petros,

New member here, bought an 85 off member Langsmer a couple of weeks back. Loving this little machine but have had some shifting roughness, read all about doing the gear flush and decided I will give it a bash and see if it helps.

I have all the service records since the car was new and couldn't find any invoices stating a gear oil change, except for one where they replaced the rear axle bearing and quoted 3qts of GL5 under parts (not sure if that was needed for the bearing job or they also did a tranny fluid replacement), otherwise I might have missed it amongst the large pile of paperwork, the lady who owned it most its life seemed to be quite diligent about services etc.

I decided to just do it anyway to be sure. I drained out about 2 qts of old oil which was pretty dirty, the drain plugs had a fair bit of metallic sludge around the magnets too. I added 2 qts of ATF (I realise this was a mistake, shoulda drained it completely and added new cheap oil/atf mix) and drove for about 50 miles and she shifted like a dream, the most problematic shift for me was always 4th to 3rd but now she was changing down like a dream. So I thought great time to drain the flush out and add the 80w90 I bought from https://www.walmart.com/ip/Super-Tech-8 ... n/16795067, the result was rather disappointing.

The problematic shift is just as before, a little grindy. I mean I can get by driving like that but hate to think I am damaging the synchro slowly.

What are your suggestions to get her back to shifting great again?
I was thinking:
- Add a bottle of ATF or
- drain out half the cheap walmart fluid and mix with a good synthetic or
- add a quart of Lucas heavy duty oil stabilizer :?
- drain out 2 qts of the new 80w90 add in 2 qts of ATF and do a second flush?

Your advice would be really appreciated, trial and error is expensive and the process is a PIA.

Also thank you for all the advice you give on here, I took your advice to hang bottle of warmed oil from the hood and fill into the front filler plug behind the diff housing and it worked a like a charm. My filler plugs took me hours to get loose, had to go buy a blow torch and heat one up to break it free.

Live in Portland, OR the car has +/- 140,000 miles.
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irowiki
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Re: Synchros -any availability? potential fixes?

Post by irowiki »

Did you do the 50/50 ATF/Gear lube flush yet?
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Re: Synchros -any availability? potential fixes?

Post by Petros »

I was away from my computer for a few days (I climbed mt. Adams on tuesday, and skied down from the summit!). so I just saw your post now.

I found that if I use one quart of ATF with 3 quarts of 85-90 gear lube it helps shifting.

the synthetic will make it worse because it is slippery and the syncro will not grip as well (it works by gripping the next gear to spin it to match the speed, to "synchronize" the new gear speed), it depends on some friction to work. ATF is designed to work with friction clutches in the auto trans, and tends to help the grip of the syncro.
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'92 Mazda MPV 4wd (wife's daily driver)
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Re: Synchros -any availability? potential fixes?

Post by knot2shabby »

Thanks Petros.

I'm gonna drain out 1 quart of mtf and add 1 quart atf. Is there any specific ATF you suggest ? Whats your opinion on that cheap Walmart GL5 I used, no good?
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Re: Synchros -any availability? potential fixes?

Post by knot2shabby »

irowiki wrote: Thu May 30, 2019 11:24 am Did you do the 50/50 ATF/Gear lube flush yet?
Yip I kinda cheated a bit though, I drained out half the old mtf and added 2 quarts of atf then drove for 50 miles, she shifted beautifully for those 50 miles. Then I drained it all out and added 1 gal of cheap Walmart GL5 MTF. Now the shifting is sticky. Especially when cold and changing from 4th to 3rd.
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Re: Synchros -any availability? potential fixes?

Post by irowiki »

Can't cheat it, gotta drain it all, 50/50 fresh atf and fresh gear lube!

Yeah do one quart atf and three gear lube. The cheap walmart stuff is perfectly fine.
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Re: Synchros -any availability? potential fixes?

Post by knot2shabby »

irowiki wrote: Fri May 31, 2019 9:10 pm Can't cheat it, gotta drain it all, 50/50 fresh atf and fresh gear lube!

Yeah do one quart atf and three gear lube. The cheap walmart stuff is perfectly fine.
Thanks irowiki,

Since the oil I have in now is basically new, I'm gonna drain half and add 2 qts atf back and drive it for 100 miles or so, drain and add 3.1 qts of sta lube GL4 85w90 (already bought it, too late) and 1 Qt Castrol transmax high mileage atf.

I will report back on the results asap.

Apologies to the OP for hijacking this thread somewhat.
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Petros
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Re: Synchros -any availability? potential fixes?

Post by Petros »

the "cheap" wal mart gear oil is pretty decent actually, they have one of the major manufacturer's package it for them.

the ATF inproves grip for clutches in the auto trans (and works on sycros as well). we used to run 50/50 atf gear oil in the race car trans to improve high speed shifting. not sure I would run that on a daily driver, ATF is only about 5 wt oil. but running 1:4 ratio I would think is okay, that is what I have now and cold shifting is much improved.
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'84 Tercel 4wd (daily driver, with on going mods)
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Re: Synchros -any availability? potential fixes?

Post by knot2shabby »

Petros wrote: Mon Jun 03, 2019 7:33 pm the "cheap" wal mart gear oil is pretty decent actually, they have one of the major manufacturer's package it for them.

the ATF inproves grip for clutches in the auto trans (and works on sycros as well). we used to run 50/50 atf gear oil in the race car trans to improve high speed shifting. not sure I would run that on a daily driver, ATF is only about 5 wt oil. but running 1:4 ratio I would think is okay, that is what I have now and cold shifting is much improved.
Great info Petros, thank you.

Apparently the you cant cheat the flush like I did, so I did it again with the fresh MTF/ATF and rode it 100 miles, yesterday I drained it out and added 3 quarts sta lube GL4 and 1 quart Castrol high mileage ATF.

The shifting does seem better on average, strangely enough some of the shifts that were not originally sticky are ever so slightly sticky now but the problem shifters are now less sticky, which I guess is strange but preferable.

One other thing I noticed when I drained out ATT/MTF mix I noticed a few spots of red oil in the area where the rear drive axle connects to the transmission - I am hoping this will go away with the thicker oil now in.
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Re: Synchros -any availability? potential fixes?

Post by irowiki »

It could also be your transmission is just THAT dirty.

My first tercel would pop out of 2nd or 3rd and she had 250k miles, and the fluid had not been changed in a LONG time, it was so dirty it took four flushes to get all the crap out, and it fixed most of the issues.
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Re: Synchros -any availability? potential fixes?

Post by Petros »

keep an eye on that rear seal. the worst thing you can do is allow the trans to run low on lube. it will damage it, and they are not making any more of them.

the rear seal is a fairly easy replacement, you remove the drive shaft, and than wiggle off the metal dust collar and replacing the seal is fairly straight forward. make sure you lubricate with gear oil it before you put the drive shaft back in.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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