TKO600 Synchronizer Blocker Ring Issue
 

The TKO600 in my 64 LeMans has less than 600 miles on it, 200 hundred of which were me driving it. I bought the car from a friend who had the trans installed in 2019 and it sat for a couple of years while other work was done on the car.

When I acquired the car in October of 2022, I noticed a that under spirited driving it grinds on the 2-3 shift. I have the sales receipt from Modern Driveline and it has the carbon lined Synchronizer blocker rings on it. Today I called Modern Driveline and the tech said they had issues with bad Synchronizer blocker rings from a particular company and the grinding is a well documented issue so they don’t sell them anymore. Further, he said the problem will not resolve on its own. He reviewed the invoice for my trans and confirmed it has the bad Synchronizer blocker rings. He said the blocker rings in question were used by other Vendors so this serves as a PSA for TKO owners.

I’m SOL cause it’s out of warranty. They offered me the factory style blocker rings at no cost or a proven good set of carbon lined Synchronizer blocker rings, at their cost of $35 each - so I opted for those.

The tech said replacing the Synchronizer rings is a job I can do at home. Has anyone done this upgrade and if so how difficult. FWIW, I’ve rebuilt engines and pretty much all other services on these cars minus transmission and rear rebuilds.

You will be able to do the change. You can download a manual and there are videos available on youtube. They use an anerobic sealer instead of gaskets that you will need, just go slow and take lots of notes. They are more complicated than a muncie. Replace all the blocking rings with the carbon lined ones while you are in there. Also, get the brass shifter fork tabs.

I wonder if this is why mine scratched??

What is "scratched"?

I asked the tech for brand of the bad synchro rings vs the good ones - his reply:

the bad synchro rings were Rockland standard gear out of New York.

http://www.rsgear.com/

The one we just sold you are from Liberty High Performance.

https://libertysgears.com/

Thanks for that Will, I just contacted Liberty and left a message.

Made a scratching noise while shifting at high RPM

Depends.

I'm sure Will has probably already been through this but there are a couple of critical things with TKO's on setup that need to be spot on before digging into the guts of the trans as a probable cause.

First the bell has to be dialed in. These transmissions use a taper front input bearing, not a ball bearing like a muncie. So it's critical the bell is within spec centered with the crank. I think Tremec likes to see it within .004-.005" max runout. Anymore than that and it's likely going to have shifting problems as that will put a lot of side load on the input shaft. Nearly every bell I've ever checked needed adjustable dowels, even OEM stuff.

The only other issue would be clutch release and that goes with any transmission. If it's not releasing properly then I don't have to tell you that will cause difficulty shifting.

The achilles heal with these TKO's has always been the size of the gears vs the size of the syncro. They increased the size/width of the gears in these transmissions to increase the strength, which makes the gears heavier. But they didn't increase the size of the syncro. They are still using the same size syncro found in a Muncie or Top Loader, which has smaller gears in comparison.
So the syncro has to work much harder to slow the gears down in a TKO, hence the reason early on why there were complaints of high rpm shifting and literature many times listed these transmissions as 5500 or 6000 max rpm shifting.
The cure became upgraded syncro materials, carbon fiber linings etc.... can't increase the size unfortunately but better materials have helped.

Sounds as though Will has found there may have been a bad batch of syncro's in the supply chain. :thumbup: I haven't heard back from Liberty yet and don't suspect I will today with the time difference. Maybe tomorrow.

Thanks for the info, Larry. I haven’t removed the gearbox just yet to check the alignment. I’ve been advised the fella who put the trans in was “anal” about aligning it and worked on it a couple of days, but I can’t personally vouch for him. Of note, the bell housing is factory style but looks new as do all other trans and clutch components since this was originally a 2 pedal car. I’m anxious to hear what Liberty says about this alleged bad batch of synchro rings. Based on you post, seems it be best for me to check alignment and clutch before anything else. Or should I plan to change out the synchros anyway and check the alignment for good measure.

While I have your attention, have you swapped the synchro rings before on your own and if so can you opine on how the job went?

Before going through the trouble of aligning the bell, take a peek at the dowels. You'll be able to tell if they are the adjustable type, in which case you can then be fairly confident someone went through the trouble to get it right. If they appear to be stock dowels, then alignment might be something you want to check but from your description and what you've been told already, it might just be a syncro deal.

Yes I've had them apart, they aren't horrible. Just a little more to them going on inside than a muncie. There are a ton of really good videos that show it better than I could explain it. Paul at 5speeds.com is a great resource. I've bought parts from him in the past, great guy and good tech support. Believe he still has a youtube channel.

Are you waiting to hear back from Liberty too? Or were you just going to buy stuff from MDL??

If you're waiting to hear from Liberty, and I'm waiting to hear from Liberty, they are going to wonder why the sudden interest in syncros :D

Can you tell by this pic if they are adjustable?

Yep that's adjustable. :thumbup:

Starting to sound more like a syncro situation.

Thank you

:beerchug:

I have the order for the synchros in with Modern and haven’t called Liberty. I am curious if they can corroborate the bad batch story even though that was a competitor.

I haven't heard anything from Liberty yet :noidea:

Still nothing.....

Well,
After no success trying to get a hold of someone at Liberty that could answer my questions, I contacted American Powertrain just a few minutes ago since I've dealt with them the most, and I got answers right away. Also contacted them just out of curiosity to see if I would get any sort of admission on this issue from another source.

Sure enough, similar to what Will has found, he stated the old rings were a spray on liner that just didn't last long. The new rings come from Liberty and are a glue on carbon fiber paper liner that are more durable.

I was offered a set of 4 for $47 each and a set of 8 solid billet shift fork pads that are $15 each. An upgrade over the old bronze pads they used to offer.

Shipped to my house $215 total

Thanks for the follow-up! And didn't realize billet shift fork pads were available - will have to look into those. Are you installing 4 synchro rings (2,3,4,5)?