Trans Synchro Ring Wear

[Mac VP]

We've noticed many posts that involve synchronizer ring questions. One issue that is hard to describe is the internal wear of the bronze ring itself, and the effects on shifting that result from excess wear.

The two synchro rings in the Ford transmissions from 1939 on are made of a bronze alloy. They are positioned in the transmission next to the hardened steel cones of second gear and the main drive gear. The gripping action against the cones when shifting is the force that equalizes the speed of those two gears with the speed of the mainshaft.

Because the bronze material is softer then the hardened steel cones, the synchro rings wear out eventually. This is by design.....you want the inexpensive bronze part to wear before the expensive steel gear wears. Of course, this is really just a comparison of parts costs. The reality is that the overall labor and time to open up the trans, tear it completely down, replace the synchro rings, and put it back together is a major cost for the owner. However, a necessary cost when the shifting action no longer provides a smooth, quiet shift due to worn synchro rings.

The following two photos show examples of a well worn ring and a brand new ring. Both are fitted to the cone on the same intermediate gear. Note the lack of a gap between the two parts on the worn example. This synchro will never do its job.....the trans will virtually always crunch when shifting into second gear. The second example shows the gap you want to see on a new synchro ring. When examining a used transmission, with the cover off, you can look at this fit on each ring. It is helpful to move the ring closer to the gear's cone to get the best look at any potential wear.

 

[green50]

Thanks for a great explanation and photos on this subject. It is very helpful in understanding the synchros.

 

[39portlander]

Great info/picture thread Mac, will print it off and keep in chapter 3 pg.24

I have a few Model A transmissions that I've been looking into, maybe an "In's and Out's" version in the future. Scott

 

[Old Henry]

The "make it or break it" for my synchronization was the spacer ring, #7069 in the following diagram.

Even with new syncro rings I had no syncro action until I replaced the standard thickness spacer ring with a thicker one to get the clearance below 0.008" on the main shaft as illustrated and explained below.

Once I put that thicker spacer in, my syncro worked great. Sure was a relief from having to double clutch every time I went from 3rd to 2nd.

P.S. Got the thicker spacer from VanPelt as I do all of my transmission parts.

 

[Admiral]

This is an invaluable thread, especially for those that plan on getting at the guts of their car's transmission. I just ordered a bunch of parts from Mac including new blocker rings and I'm sure glad I got a set because the ones that came in the transmission only provided about 0.015" of clearance between the gear face and the ring, far from the 0.060" to 0.080" required. A visual inspection of these components revealed no obvious flaws. This is not a job I want to do every other week so it's well worth spending a couple extra bucks on good parts that will last.

 

[jake197000]

great explanation.i buy my parts from mac also.he has good stuff and knows his stuff.do u think the quality of the materials is as good as original?idont think it is,but the cars dont get driven as they used to for the most partso they work ok.

 

[Old Henry]

This is an invaluable thread, especially for those that plan on getting at the guts of their car's transmission. I just ordered a bunch of parts from Mac including new blocker rings and I'm sure glad I got a set because the ones that came in the transmission only provided about 0.015" of clearance between the gear face and the ring, far from the 0.060" to 0.080" required. A visual inspection of these components revealed no obvious flaws. This is not a job I want to do every other week so it's well worth spending a couple extra bucks on good parts that will last.

Be sure and check that clearance on the main shaft I mentioned and get the thicker spacer if needed. The first two times I rebuilt my transmission I didn't and rued the day.

 

[VeryTangled]

Hi Everyone! I had to try to explain synchronizers to a class of students tonight. Hard stuff.

This video starts sorta slow but let it run... As good an explanation as any about how the synchros work. It doesn't address how they hook to the output shaft unfortunatel

Somebody needs to get this guy a lozenge. This is not me talking.

https://www.youtube.com/watch?v=vOo3TLgL0kM

 

[Admiral]

Be sure and check that clearance on the main shaft I mentioned and get the thicker spacer if needed. The first two times I rebuilt my transmission I didn't and rued the day.

Oh yes, I made sure to order a thicker thrust washer as well. It was $6 well spent if I need it.

 

[sidevalve8ba]

Excellent information, Mac. I've got a '39 top-loader I need to go through one of these days and I will keep this information handy. Thanks.

 

[V12Bill]

I have just rebuilt the transmission in my 1939 pickup and am ready to install it. I do not have the .060 to .090 gap between the syncronizer ring and the main drive or the second gear even though I replaced both bronze syncronizer rings. I have .006 gap between second gear and the thrust washer where the requirement is .004 to .008. I have replaced the 7069 washer and the front and rear cluster gear thrust washers as well as all of the bearings . Are my main drive gear and second gear worn bad enough that new syncronizer rings will not correct this situation?

 

[Ol' Ron]

Don't ya love it, when you learn sumpin new every day.

 

[LOWRIDER]

V12 Bill. In my 45+yrs working as a mechanic I've found that many times the "soft will wear out the hard" in situations like yours. A couple examples are the front cover seal wearing a groove in the crankshaft damper and the pinion seal wearing out the driveshaft yoke. Same holds true with blocking rings. When going thru a trans and running into a situation like yours we had to determine which part was worn. You always had a spare good ring laying around to ck which was worn. Customer usually got both pieces unless you could tell one part was really toasted. You didn't want the customer to comeback mad and lose 1/2 a day fixing it free.

 

[D. Jones]

Is there a place on this site where this type of information is available/cataloged for easy reference including measurement and fit for transmissions, carburetors, brakes etc.? If there is I've not found it. If not, would that be possible? Sure would save some of us a lot time looking and asking the same questions over and over. I'm aware of Van Pelts site and that information is helpful but, sometimes a more detailed description is given here by very knowledgeable folks which clears things up faster for some of us.

Just my $0.02 worth.

 

[rotorwrench]

As far as transmissions, Mac VanPelt's book is the best reference. To put all that info on this site would take too long and rob too much band width. You just can't beat MVP's book. They are available from a lot of parts vendors as well as from Mr VanPelt's web site.

For the other items, you need the specific manuals for the vehicle being worked on.

 

[V12Bill]

I just got off the phone with Mac Van Pelt about my problem with the blocker rings in my transmission. It seems that the repo blocker rings are made way off shore and are not up to specs. Surprise, surprise. Mac has the correct size blocker rings that will give you the correct space of .060 to .090 between the blocker rings and their corresponding mating cone. He also stated that it is very rare to have wear on the mating cone/gear as the steel is VERY hard. I just ordered a set of rings from Mac and will get back to my PU when they arrive. Thanks for the suggestions from others.

 

[Ian NZ]

A few years ago I reconditioned one of my V8 Gearboxes replacing several parts and fitting new synchro rings and changing gears was alright for awhile, and then it was getting harder and harder to change into 2nd and top gear and someone suggested worn synchro rings, which I could not believe, so I removed the gear gearbox and dismantled it, and I found that the new synchro rings were worn out after 200 miles, the bronze in them was too soft, I admit I changed gears quite often, changing the grade of oil etc, trying to find the fault in the gearbox. I then fitted a good set of synchro rings out of another gearbox and now I can change gears easily, problem solved.

 

[Talkwrench]

In that diagram I think there is a ring that is missing , slides on the end of the main shaft snout before bearing 7118 goes on ?

 

[V12Bill]

I think you are right. Its is more of a spacer ring than a retaining ring. A cross section of the ring would be round instead of square. It goes on the snout of the output shaft just behind the 7118 bearing.

 

[trucker1]

Amen on Mac's transmission book, it's awesome.