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Gearbox Syncros

Joined
11 March 2007
Messages
3,203
Location
Toronto
Hi All,

My car grinded whilst shifting into 5th gear this past weekend so I've monitored it and its happened again. With that being said the car was going in for major electrical diagnosis and I asked the shop to see if it was my short shifter or bushings making the grinding. Nope. Short shifter is fine, bushings are fine, cables are fine, but the syncro needs to be replaced.

Has anyone had to replace their gearbox syncros?

Should I replace all of them as the gearbox is out?

Can you purchase the syncros as a set from Acura or individually?

My workshop manuals are at the shop as I lent them to my mate for the electrical diagnosis issues so I haven't had a chance to look at the gearbox related stuff.

Any suggestions or comments would be great!

From re-doing the exterior and interior now diagnosing the electrical gremlins and further gearbox work I'll never get to drive the car!!! Hehe...Its like I've opened a Christmas present and not been able to play with it... ;)

Thanks,
Jetpilot
 
It never ends with this car let me tell you. But when she's done brand spanking new baby.

Syncros are $600? Wowzers...don't think I need a whole new transmission though...
 
Have you serviced it since you've owned it? It's just a thought but it never hurts to try. I'd take a close look at the clutch wear while it's down.
 
It never ends with this car let me tell you. But when she's done brand spanking new baby.

Syncros are $600? Wowzers...don't think I need a whole new transmission though...

Never heard of syncros going bad? When I replaced my snap ring Trans w/50k, My syncros were the same spec as my new OEM ones that replaced them. PM Larry B and see what he has to say, he has replaced cars w/100k+ that the syncros were still good in. I think its more of a hydraulic issue then the Trans
 
Yup the car has been serviced since being in Dubai. The shop has said that everything else appears fine in the gearbox but the syncros are done for 5th gear. So...while its out maybe purchase them all.

With that in mind I'll PM Larry B...cheers!
 
Yup the car has been serviced since being in Dubai. The shop has said that everything else appears fine in the gearbox but the syncros are done for 5th gear. So...while its out maybe purchase them all.

With that in mind I'll PM Larry B...cheers!

Synchros and the teeth on the hub selector wear eventually. If you're rebuilding the tranny it would be insane not to replace them all. They should almost always be replaced during a standard rebuild. Since you presumably have the original synchros I'd strongly recommend it. The worst thing in the world would be to start feeling a synchro a month later that was fine before the rebuild. :frown:

If the 5th gear synchros are the worst that would indicate that you do a lot of downshifting from 5th gear to a much lower gear. The bigger the gear difference the harder the synchros have to work.

In the future you might want to put the gearshift into neutral, let off the clutch and depress the clutch again to complete those extreme downshifts. This is called double-clutching and effectively removes synchros from the shifting equation.

Drivers who don't downshift much or double-clutch frequently will generally get much more mileage out of the synchros which is why you'll often see trannys with well over 100K with minimal synchro issues. Mine has 130K and I feel very little resistance/grinding if any while shifting, but I frequently double-clutch. Driving style has a huge impact on tranny wear. :wink:

And while you're in there you might consider the Japanese short gears and the 4.235 R & P. Each is about ~$700. Get Dave's short shift block and the car will feel very different (in a good way!)
 
my fifth gear synchro grinds, but only when shifting into 5th at above 100mph. i'm gonna try the synchromesh solution to postpone having to take the trans out again (just replaced the clutch not too long ago, and that's when it started doing it :mad: )
 
my fifth gear synchro grinds, but only when shifting into 5th at above 100mph. i'm gonna try the synchromesh solution to postpone having to take the trans out again (just replaced the clutch not too long ago, and that's when it started doing it :mad: )


The Synchromesh fluid has eased the symptoms for many owners. I'd definitely recommend trying it.
 
Yea I've had great results with synchromesh and frction modifier that Rob (RON98) put in my tranny... I was afraid that I might needed a rebuild as well but so far so good! Its been smooth for 2-3 months now.

But if you must rebuild, I agree, why not put in the short gears and NSX-R final drive! :D
 
The Nsx transmission is very reliable. I am guessing most these issues are a result of tranny oil not being changed and burning up or operator error during shifting, possibly not depressings the clutch all the way while up/downshifts. The car should shift like butter even if it has less than 100k miles even during spirited driving click click thats all you should hear.
 
HI Guys,

I've hardly driven this car since owning it (3-4,000 miles) and will follow the advice for downshifting. That being said my car already has the short gears (4.23) and I'm confused regarding having to rebuild the tranny already!!!

Mark Basch did the Short Gears and 4.23 Ring and Pinion back in January of 2003 with the brand new Center Force Clutch. Its already worn?!?! Can't be can it?...I have the specific break down of what was installed (definately a whole new transmission).

I seriously thought it was the clutch (hate the Centerforce clutch) but the shop said its fine.
 
HI Guys,

I've hardly driven this car since owning it (3-4,000 miles) and will follow the advice for downshifting. That being said my car already has the short gears (4.23) and I'm confused regarding having to rebuild the tranny already!!!

Mark Basch did the Short Gears and 4.23 Ring and Pinion back in January of 2003 with the brand new Center Force Clutch. Its already worn?!?! Can't be can it?...I have the specific break down of what was installed (definately a whole new transmission).

I seriously thought it was the clutch (hate the Centerforce clutch) but the shop said its fine.

Yea man I'd throw some synchromesh in there and see how it goes :)
 
HI Guys,

I've hardly driven this car since owning it (3-4,000 miles) and will follow the advice for downshifting. That being said my car already has the short gears (4.23) and I'm confused regarding having to rebuild the tranny already!!!

Mark Basch did the Short Gears and 4.23 Ring and Pinion back in January of 2003 with the brand new Center Force Clutch. Its already worn?!?! Can't be can it?...I have the specific break down of what was installed (definately a whole new transmission).

I seriously thought it was the clutch (hate the Centerforce clutch) but the shop said its fine.

Well, first off your tranny is probably fine. It's the synchros or worn teeth on the hub selector. I'd go over the work order or give MB a call and ask him if the synchros were replaced in the rebuild. But synchros do wear. It's like saying that your brakes are totally shot because you need the pads replaced. Not exactly analagous as obviously any tranny work is very invasive as opposed to popping a caliper off. :wink: The synchros are essentially wear parts inside the tranny.

If the synchros were replaced by MB I honestly would be surprised if after 4000 miles the synchros are acting up. It could be a bad synchro...I'd say it's possible but 4000 miles is not a long time even considering an overly abusive driving style.

I'd have someone who really knows NSX trannys drive it to confirm that it is a synchro problem. Before anything however I would definitely recommend the GM Synchromesh formula (1 part GM Friction Modified & 2 parts GM Synchromesh [GM part #s 12345349 & 12377916, respectively] and see if the problem doesn't all but vanish.
 
Well, first off your tranny is probably fine. It's the synchros or worn teeth on the hub selector. I'd go over the work order or give MB a call and ask him if the synchros were replaced in the rebuild. But synchros do wear. It's like saying that your brakes are totally shot because you need the pads replaced. Not exactly analagous as obviously any tranny work is very invasive as opposed to popping a caliper off. :wink: The synchros are essentially wear parts inside the tranny.

If the synchros were replaced by MB I honestly would be surprised if after 4000 miles the synchros are acting up. It could be a bad synchro...I'd say it's possible but 4000 miles is not a long time even considering an overly abusive driving style.

I'd have someone who really knows NSX trannys drive it to confirm that it is a synchro problem. Before anything however I would definitely recommend the GM Synchromesh formula (1 part GM Friction Modified & 2 parts GM Synchromesh [GM part #s 12345349 & 12377916, respectively] and see if the problem doesn't all but vanish.

Ahhh thanks for the clarification ;) The shop is saying that the Syncromesh would help and I'm free to order it and try but its not getting rid of the main problem. What do you suggest?

Hmmm...I'll place a call to MB this evening (am in U.S.) and see if he remembers if the syncros were original or not.

Thanks for the help!
 
Ahhh thanks for the clarification ;) The shop is saying that the Syncromesh would help and I'm free to order it and try but its not getting rid of the main problem. What do you suggest?

Hmmm...I'll place a call to MB this evening (am in U.S.) and see if he remembers if the syncros were original or not.

Thanks for the help!

Well, we're not really sure what the "main problem" is yet.

If the Synchromesh gets you 15K more miles without feeling the synchro I'd say it was the perfect temporary solution, but hey, everything's temporary--the synchros aren't going to last forever, after all.

If the synchro(s) are bad, they're bad. The tranny will have to be opened up to deal with that. If Synchromesh can hide the symptoms of the bad synchro(s) use it--it's not like you're "ignoring" the problem--you're simply putting pressure on a fatal wound. You'll eventually bleed to death but why go sooner than you have to?
 
Synchros and the teeth on the hub selector wear eventually. If you're rebuilding the tranny it would be insane not to replace them all. They should almost always be replaced during a standard rebuild.

I have to disagree here. I just thought the same in my case with a gearbox with 50k miles. The problem was a time-related one. Ordering a synchro would mean 3-4 weeks waiting time here in Europe.

The new synchros were installed anyway but it was a shot in the oven as the 'worn' ones looked like new (according to the SM). It all depends on the history of the car. Installing them while knowing the history of the car (track?) can just be throwing parts at the car. In doubt: replace them.

I'm a little bit asthonished about JetPilot3's car. It's like going around circles, the problems and the incentive to solve them.
 
I have to disagree here. I just thought the same in my case with a gearbox with 50k miles. The problem was a time-related one. Ordering a synchro would mean 3-4 weeks waiting time here in Europe.

The new synchros were installed anyway but it was a shot in the oven as the 'worn' ones looked like new (according to the SM). It all depends on the history of the car. Installing them while knowing the history of the car (track?) can just be throwing parts at the car. In doubt: replace them.

Well, I'm not exactly disagreeing with you. In your case there was a logistical issue in simply obtaining them. In this scenario not replacing them might have been the better option. But they do wear and while the tranny is open, particularly on an older car with original synchros one should strongly consider replacing them. An NSX with only 50K miles and that's shifting smoothly at the time of the rebuild might be fie without new synchros. By the time they become a problem it might be time for the next rebuild anyway. :wink:

But I see it more like the water pump issue. Yes, in many cases replacing the WP might be "throwing parts" at the car but it's a few hundred dollars for peace of mind and the timing belt labor overlaps. The tranny being open is a great opportunity to replace the synchros and it should be considered.
 
What would be the arguments for new bearings?

WP: it's about $200, so no brainer compared to the labor involved. I see a slight difference between the WP and the syncros as with later ones you have more possibilities or time to react while the leaking WP has to be replaced soon.

BTW I did mine too but it was overkill again.
 
What would be the arguments for new bearings?

WP: it's about $200, so no brainer compared to the labor involved. I see a slight difference between the WP and the syncros as with later ones you have more possibilities or time to react while the leaking WP has to be replaced soon.

BTW I did mine too but it was overkill again.

Yes, there is a substantial price difference which is why it's not 100% analogous but I've heard very few stories of the water pump actually failing. One could definitely argue that it's unnecessary every time. But everyone does it as they should.

True, unlike the water pump the synchros go gradually but the point is the same. Driving around with bad synchros is no fun and why be forced to wait for years to do another tranny rebuild? Or have to pay for another rebuild prematurely?

You know the synchros are going to wear and unless the synchros are low mileage or not that old for $600 I'd say it's well worth it. You're insuring that the tranny will be problem-free another 100K+ miles.
 
I have to disagree here. I just thought the same in my case with a gearbox with 50k miles. The problem was a time-related one. Ordering a synchro would mean 3-4 weeks waiting time here in Europe.

The new synchros were installed anyway but it was a shot in the oven as the 'worn' ones looked like new (according to the SM). It all depends on the history of the car. Installing them while knowing the history of the car (track?) can just be throwing parts at the car. In doubt: replace them.

I'm a little bit asthonished about JetPilot3's car. It's like going around circles, the problems and the incentive to solve them.

Your astonished? Try its owner - me! Its not like there isn't incentive to solve these issues as my car had been laid up in the interior upholstery shop for the last 4 weeks (hence why no posting regarding the electrical gremlins). Don't worry mate its all being worked on now so I'll keep you posted as to what we find out.

Problem after problem (somewhat expected on a 17 year old car) so I've got the car into the shop and I'm having everything fixed.

The electrical gremlins - being worked on at present, the Gearbox issues - just came up last weekend while on a drive from the interior shop to the service center for the electrical gremlin issues and A/C issues. As for the A/C we are doing the R134 conversion and the car blows ice cold now - ahhhhhh lovely in Dubai. The drivers side door switch killed over last week so I had to order that along with the R134 conversion kit (passenger window wouldn't go up).

So...I pick her up this week and she should be okay until the Syncros come in as I'll simply order those for the $600 it will cost and have it done. The shop swears on the syncros so why not and maybe then I'm ensuring the gearbox will remain tip top shape for years to come (no plans on selling my pride and joy).

Trust me I'm receiving lots of ribbing from friends with other makes...pressure is on to prove Honda reliability.

Thanks guys!
 
Your astonished? Try its owner - me! Its not like there isn't incentive to solve these issues as my car had been laid up in the interior upholstery shop for the last 4 weeks (hence why no posting regarding the electrical gremlins). Don't worry mate its all being worked on now so I'll keep you posted as to what we find out.

Problem after problem (somewhat expected on a 17 year old car) so I've got the car into the shop and I'm having everything fixed.

The electrical gremlins - being worked on at present, the Gearbox issues - just came up last weekend while on a drive from the interior shop to the service center for the electrical gremlin issues and A/C issues. As for the A/C we are doing the R134 conversion and the car blows ice cold now - ahhhhhh lovely in Dubai. The drivers side door switch killed over last week so I had to order that along with the R134 conversion kit (passenger window wouldn't go up).

So...I pick her up this week and she should be okay until the Syncros come in as I'll simply order those for the $600 it will cost and have it done. The shop swears on the syncros so why not and maybe then I'm ensuring the gearbox will remain tip top shape for years to come (no plans on selling my pride and joy).

Trust me I'm receiving lots of ribbing from friends with other makes...pressure is on to prove Honda reliability.

Thanks guys!

Hang in there! Electrical problems are unusual but AC is not. I've had my share of gremlins too. It's absolutely to be expected on a 17 year old car. But it's all stuff that eventually goes. My windows, door handle bracket, ABS, starter, seat belts, Bose speakers etc. have all gone out at one point or another. But once you fix them it'll be fine. These things happen on even the world's most reliable cars after 17 years. But I have never had anything major just go out unexpectedly.

I do feel for you on the electrical. There's nothing harder to diagnose than electrical. I only take my cars to an electrical specialist if there's any issues. Even crackerjack mechanics who know everything about the NSX can struggle on electrical. All you do is end up wasting time and money while your mechanic essentially tries to guess at treatments and use trial-and-error repairs. :rolleyes: It's a very specialized area of expertise and can be very frustrating. I was a mechanic (not cars) for years and electrical was not my forte. Nothing I couldn't do otherwise and I could operate a meter-reader but I began to truly understand the difference between a mechanic and electrician. :wink:
 
You know the synchros are going to wear and unless the synchros are low mileage or not that old for $600 I'd say it's well worth it. You're insuring that the tranny will be problem-free another 100K+ miles.

I agree with your point. How long should synchros last? I can agree on 100k miles while normal driving. How long are they built for? I guess much more than 100k miles.
If your synchros look like they're going to hold up the next 50k miles would you install brand new ones? I wouldn't just because the clutch is out during this time for high probability and working on the gearbox then is quite easy then.

A car with bad synchros can be driven if you shift very slowly in the specific gear. It's no fun in a sportcar, ok. But having the WP or the tensioner looked up will cause a major pain in the money pocket, even rediculous pain because they're $300 or so. Driving with bad synchros eats up money as well but only a few $1000.
 
I agree with your point. How long should synchros last? I can agree on 100k miles while normal driving. How long are they built for? I guess much more than 100k miles.
If your synchros look like they're going to hold up the next 50k miles would you install brand new ones? I wouldn't just because the clutch is out during this time for high probability and working on the gearbox then is quite easy then.

A car with bad synchros can be driven if you shift very slowly in the specific gear. It's no fun in a sportcar, ok. But having the WP or the tensioner looked up will cause a major pain in the money pocket, even rediculous pain because they're $300 or so. Driving with bad synchros eats up money as well but only a few $1000.

Yes, you can limp through with bad synchros unlike a failed water pump. Driving style plays a large part in synchro life just like clutch life. It's hard to say how long they're "built for".

If I thought I had 50K left on the synchros I'd probably wait as well because that would be about 5+ years of driving for me and I am very easy on the synchros anyway. But the OP already has a synchro problem and the car probably has the original synchros. If the tranny is going to be cracked open I say replace them. But I would try the Synchromesh before that if the 5th gear synchro is the only issue in the tranny.
 
Hey Cameron, you should have all your gears cryo treated before you rebuild your transmission. This will make the parts extremely tough and resistant to wear. I had my rotors and pads cryo'd and it took them about 500 miles to break them in! :eek: Good luck!
 
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