Topic: r154 5th gear synchro

[modernmuscle]

I am assembling my r154 after upgrading the shift forks, thrust washer, and all new bearings. Almost done and I notice the 5th gear fork is slightly engaging the synchro making it drag in the neutral position. I have read about others having this same problem but no fixes. I would hate to continue putting it together and have an issue.  Any ideas?

~Lee

[BigMike]

Lee, I'll see if I can get Marlin or Chris to chime in here with some advice tomorrow

[modernmuscle [OP]]

That would be great!

[BigMike]

Lee,

Ok, I spoke to Chris and he has a few questions but first he'd like to now what year is your transmission? Short of not knowing that, he thinks you might have installed the 5th gear fork backwards. The bolt that secures the fork to the shift rail is not exactly centered, and if the fork is flipped 180-degrees, then you would have contact ... but Chris says you would have considerable contact, not just light dragging.

Let us know the year and also maybe reply with a picture of the 5th gear fork area.

Thanks!

Mike

[modernmuscle [OP]]

The tranny is out of an 89 Toyota supra turbo. Im pretty sure I tried the fork both ways and determined one of them was definitely not right. I found another person through google search who had the exact same problem and actually put a video on youtube.

called r154 issue I personal messaged him on the supra forum where he asked this same question a few years back and replied back today saying he ended up putting it together and it was fine. 

The syncro doesn't drag really bad unless you spin the input shaft backwards , then it gets worse. Right now the cases are bolted together. Thinking maybe if I get the front bearing retainer and all bolted together it may make clearance between the 5th gear and synchro.  Oh and the new synchro drug a bit more than an old one I put in.

Thank You!
~Lee

[BigMike]

Lee,

I spoke to Marlin about this and I didn't even have to finish my sentence and he told me all about it. There is an actual issue with the design of certain components in early R154 transmissions that cause this to happen. Marlin said it took him a while to figure out how to fix it and as such it is one of our trade secrets. I know this is not the answer you are looking for but Marlin was quite defensive about his discovery (and for very good reasons as we remedy this issue on all of our transmission rebuilds / we protect what we do to ensure our transmission rebuilds truly are the best).

His only advice is to do what the guy in the YT video did and that is to just run it. Otherwise, if you are interested, we don't have a set service for this, but ship it over and we can fix the issue and return it to you. Labor charges for this shouldn't be that much, but we'd need to figure something out because it not something we do outside of an actual rebuild -- ie. we don't have a set 'Repair Order' for this in our sales software -- but we'd still like to extend the offer if you are interested. We would be modifying a few parts and then putting everything back together so that the issue is no more.

Let me know what you think. Marlin thinks it will be okay to go back as is, it's just possible for accelerated wear and you'd want to check your fill plug magnet more frequently than normal just to ensure consistent wear.

Good luck Lee and thank you for your replies and detailed information!

Regards,
BigMike