Hello superheroes, I recently bought my car and aside from all the other work done, I put a freshly rebuilt 39 transmission in the car. From my (naive) perspective, the transmission showed little to no wear. I was driving the car to the DMV to finish my registration (after a few months Of blood sweat and tears) when the transmission got stuck in second gear. I took the top plate off and found that one of the Synchro gears was riding upward and locked up shifting. I also discovered a small metal fragment that appears to have come from the backside of the synchro assembly block. Did I rebuild the trans correctly, do any of the photos create red flags for you? does anyone know why or how my synchro block would ride upward, lock in place, and prevent the shifter assembly from coming out of second gear? Please see the attached photos. Note: I do have and followed the vanpelt trans book. Thanks massively in advanced! Jay
I had the exact same thing happen to me last year. After seeing this I’m chalking it up to poorly made aftermarket synchronizer blocks. Assuming those are reproductions…
Had the exact thing happen in my A when first together. It was the re pop synchro rings, I don’t remember exactly of the top of my head but in the VanPelt book walks you through. Had to file them down, has specs and everything. After the re rebuild has lasted several years and many miles no problem.
Cool car by the way. Buy the book and get it back together. Labor intensive but should be relatively cheap fix and back on the road.
Looks to me like it may have too much clearance between the gears allowing the synchronizer ring to move too far.
I suspect the inner springs for the synchro are not installed at staggered locations, and/or the small bump out of the spring is not settled under an insert fully. By placing the bump out of each spring under a different insert (comparing front and rear springs) it keeps a consistent pressure on all three inserts. Once any single insert can pop up like shown in the photo, it prevents the synchro slider from shifter back to the center (neutral) position. I assume that this shifter housing has the correct original 91A-7230 shifter fork. This fork always has that part number cast into the front face of the fork. Also, it appears that the brass synchro rings are worn to the point where they practically touch the matching teeth on second gear and the main drive gear. This has nothing to do with the problem of being stuck in second gear. Just my observation. I’d replace the rings when tearing the transmission apart to fix the main problem. There were some aftermarket rings that have a poor fit (brand new out of the box). It’s hard to see if these particular rings are used or new.
Thanks everyone. Huge help and confirms my suspicions as well. - I bought new synchro blocks - will ensure the springs are staggered - I bought new synchro gears and will install them conparingthe spacing before and after. - will also check on that filing procedure as well, I don’t think my van pelt book contains that but I’ll find it. Have a wonderful day. J
Keep us posted on fixing it please! This is, and could continue to be, a valuable thread about putting together/ trouble shooting these very popular transmissions
Ok, so here’s the download on the tranny tear down today. For the record, these things are easy to work on, just go slow and take cell phone photos of the order of things. Side note: I was wondering if I had a rear main oil leak because after replacing the oil pan gasket, it still puked oil… that’s why I pulled the engine and trans together. More on that later. Forensics: - the synchro was installed correctly but one of the blocks failed within the assembly and broke. There is no explanation for the block to fail in the assembly but it did!!! See photo. - the rotation of the synchro gear against the broken synchro “block” caused substantial wear on the Synchro gear and literally turned my trans fluid into what looked like one of my 3 daughters’ experiments with syrup and gold glitter. Or, maybe a 49er’s gold pan. In other words, the entire case and trans was speckled with gold (brass) flakes. NUTS. See photos. Thankfully, I had already purchased and installed the new synchros and “blocks” with retaining rings from CW Moss. Thanks Mac VP on that tip!! They are close to me and deliver crazy quick via usps. gutted the trans entirely, cleaned it spick and span to remove the brass flake and rebuilt the trans (again). now about that rear main….. the previous owner must have forgotten to put a rear main seal in the engine or maybe aliens abducted the rear main seal. Regardless, It was NOT there! After many laughs this afternoon with my buddy who was helping me, we made a model a grocery list and I went shopping tonight. next, I’ll need to pull the crank, timing cover, etc to gain access to replace the front seal (why not? I’m in this far) and to put the rear main seal where it belongs. Or maybe the aliens will return it tonight. Hahaha. It was super fun working with a friend today, i learned a ton, and look forward to diving in further!
Engine was rebuilt within the last 2 years and never driven until I got the car back together recently. maybe there was a “shortage” but why assemble the engine without one? i like my aliens story best, it does get really dark in my garage at night and there’s lots of shiny brass dust to attract them. Hahahahha
Dreamer,,,,I was trying to be funny . The engine doesn’t have a rear main seal,,,,,that’s why they leak fairly well . Tommy
I don’t follow, so do you mean that the car isn’t supposed to have a rear main seal? I get confused easily in my old age.
Hey man, no shame in that. It initially confused me too when I tore my engine down. There is no rear main seal on a stock A. Just an oil slinger. There is a drain tube connected to the rear main cap that is designed to return any escaping oil to the pan. If that tube plugs up, you'll get an external oil leak.
Same on a B. There are modern seal kits offered for the B; they require minor machine work. Lot's of info on this on Ford Barn (Google "Model B rear main seal ford barn"). Also covered in Brierley's "Four Bangers and Me"
Hi All, I spoke with Mr Van Pelt this week about my trans and his wonderful “ins and out of early ford transmissions book” that I used while rebuilding my trans. Had a Q about the install of the internal synchro hub. We agree and possibly inferred that my synchronizer assembly block breakage may be attributed to a combo of bad luck, low quality steel reproduction parts, and/or the fact that my two synchro clips may not have been staggered in different positions. Mr Van Pelt mentioned that if the synchro clips are not staggered that they can create uneven pressure/spring tension behind the blocks and (I assume) lead to one edge of the block to “ride higher” than it is supposed to, making it susceptible to breaking. He offered some other advice on what to check for while fitting the new brass synchros on the internal hub assembly. I learned a ton from my 10mins on the phone with him and from this great community. Thank you ALL, I’m feeling pretty good about my rebuild….again
Oh and about that rear main seal…. I’m so dumb as a newbie to this model a that tonight I just realized that I’m missing the rear block insert in my engine, not just the (optional) rear main seal. I’m so clueless on the inside of this engine that I failed to see this…. Dam I feel dumb. Even with all my “how to…” manuals
The Jalopy Journal
