When is transmission gear replacement needed?

toyotanos

toyotanos

What will we break today?
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Nov 29, 2008
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Coon Rapids, MN
So here's the story: I bought a new/used R154 to replace my 212k OEM that has serious issues shifting into 2nd and 3rd. The new transmission was advertized as having a slight grind while going into 3rd at very high RPM's, so I am tearing it down and rebuilding it to hopefully make shifting smooth in all gears.

Here is where my question comes in. Since the gears have been ground, the dog teeth have some wear on the tips. The blocker rings(brass parts) and synchro sleeves will be replaced anyways, but how much damage can the gear's engagement teeth take before the gear itself needs to be replaced? I have worked on transaxles that have had the teeth completely worn flat, which obviously required replacement, but where is that line of still being reusable?

Pics to accompany story

These pictures are of 2nd and 3rd gear, looking at both gear's engagement teeth, but the blocker rings can be seen as well. Focus only on the steel(gray) synchro teeth, please **We're talking about the synchronizer system here, not the actual gears' teeth**

2nd gear:
p1791239_1.jpg


3rd gear:
p1791239_2.jpg


Any attempts to get closer shots ends up very blurred (even in macro and super macro mode) I will disassemble the transmission completely this weekend, and may have better shots then but for now lets go with these.
 
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Mr Bojangles

Mr Bojangles

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Feb 9, 2009
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Your second gear has a few teeth that are more rounded than you'd really like. From the pictures, third actually looks pretty useable.

Every trans is different though, that second would be fine on a civic, but on these that looks to be enough to cause you issues.
 
toyotanos

toyotanos

What will we break today?
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Nov 29, 2008
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I think I'm making this more confusing that it should be...:nono: I find it extremely hard (language-wise) to differentiate between the 'gear' part of the gear and the synchronizer teeth part.

My concern is whether the synchro part of the speed gear is too badly worn for the gear to be re-used, but I think Im going to try keeping the gears that are in it right now. If it grinds afterwards, that'll indicate that it needs new gears I'm OK with tearing the trans back down again.

I bought new synchronizer rings and sleeves so 2/3 of the synchro system will be replaced, only the gears will remain original.
 
Mr Bojangles

Mr Bojangles

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What you're saying is clear. Second gear looks good and third looks like it has some slightly rounded teeth and could give you grinding issues going into gear.
 
toyotanos

toyotanos

What will we break today?
Staff member
Super Moderator
Nov 29, 2008
2,842
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Coon Rapids, MN
The thrust washers are on backorder...ask me how I know :/

I think at this point I'm going to leave the gears as-is and will just redo the trans if either of them grinds. The previous owner said third grinds at very high (7500+) rpm shifts, and I'm not sure if I'll be going that high.
Technically I could have gotten away without the rebuild I'm doing but if its out might as well make it really good!
 
I

IJ.

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Mar 30, 2005
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You could sharpen up the Synchro teeth with a dremel, that'll help initial engagement, way back when I had my Z I used a steel case Toyota Trans and removed the tip of every second tooth to help with missed shifts under power.

Ugly but effective, after all I'm just a hack in a shed ;)
 
Mr Bojangles

Mr Bojangles

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Feb 9, 2009
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