4 speed info

[Toptech360]

It sounds like the 4spd transmission is the Achilles heel of many roadsters...I work on toyotas for a living and every time a scion frs/Toyota 86 manual 6spd comes in I'm tempted to take measurements, at first glance they are similar in size and shape to a datsun roadster transmission...if an adapter and custom flywheel could be made...a six speed manual roadster would be pretty sweet.

[JT68]

From looking at the photos in the link from Linda, it looks like I mis-spoke. I had only seen the roll pin counter shaft in the Warner boxes, but according to that link you could have a "roll pin style" counter shaft with a servo type synchro, so I stand corrected. Either way you need to know what type shaft it is, since it very likely will need one. Its easy to tell Warner from servo trans with just a few photos. If you are lucky and it is a Warner trans, the syncros are only about 50$ so you might do all of them if so inclined// j

[Linda]

Always worth providing the link to Rallye for excellent info on the transmissions:
http://www.datsunroadster.com/PIC_PAGES ... o_info.htm
Linda

[jarhead]

Thanks for the advice and links. I'm gonna give a go this weekend.

[jarhead]

Houston we found a problem. First, the transmission is servo, which goes along with my early 66. At first glance everything looked good. No broken gear teeth. Synchro's look reasonable to me, but quite frankly still not sure what "normal" is. ha. Anyway I took out the counter cluster shaft and well, lets just say it took took a vise grip to get it out. Wow, major wear.....

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So if I replace the shaft, bearings (dean has a shaft with two bearings, but looks like I need four?) and a couple gaskets, front seal that I suspect is worn and clutch boot, the grand total will be $345 sans shipping. What do you think?

[notoptoy]

Well congratulations for tackling this, I think it was rewarding when I did it for the first time, and not quite as hard as I was afraid of before starting. For $350 you would get a "known good" 4 speed that should serve you well for sometime to come. I would also just try and look at additional vendors for comparison, I got different parts from various vendor including Dean, Ross and the a local industrial bearing supply house.

[Linda]

I would fix what you have. Kind of depends on the wear on the gears too but Rallye has some good used parts. Then you will know what you have. This is where you spend what you have to and save money elsewhere IMHO. A new countershaft would beat most known good trannys, which I think would still be a risk.
Or some people have bought used trannys, opened them up and removed the slightly worn countershaft, added new needle or roller bearings for their original tranny and put it back together as a low cost option. As well, scavenging other parts too, which would be an idea even if you found a guaranteed good 4 speed.
My.02
Linda

[JT68]

Pretty much exactly what I thought you would find...

A used shaft is a non-starter- unless you want to do this again next year. It will fail new bearings in no-time. Waste of time/money/effort.

Suggest you shop around for the parts. Dann at Rallye has a good price on the shaft 322-48 I think. Other vendors will have them as well. j

[JT68]

Correcting the counter shaft is required. (or get a different trans)

You are at a cross-roads with this 4-speed now... if you tackle the mainshaft now, the time,effort and $$$ goes up significantly, but so does the chance of curing the original problem. If you service the 2nd gear synchro, there is nearly 100% chance of success, if you do nothing to it and, fix the counter shaft only and buy some very good gear lube, maybe 35-40%.

[jarhead]

I see. The countershaft wear is not an inherent problem to these 4 speeds? It's a synchro problem that started it. Can I tell by looking or do I have to dive into the main shaft to find out?

[notoptoy]

If the gears aren't chipped, you can try flipping the synchros, this is a no cost fix if you don't uncover any other issues.

[Linda]

Very good gear lube would be a 50/50 mix of GL 4 80-90 wt plus Redline lightweight Shock Proof? As I read elsewhere....
Linda

[JT68]

I see. The countershaft wear is not an inherent problem to these 4 speeds? It's a synchro problem that started it. Can I tell by looking or do I have to dive into the main shaft to find out?

Yes, the countershaft is an inherent problem. Not sure if its a metallurgy error or just a poor design, probably the later- but virtually every one fails.

In theory the counter gear should not affect the synchro operation, but I the real world it does since play in the counter shaft causes variations in gear lash. Professor Porsche designed a clever system, but it isn't perfect when a bunch of wear/gear lash invades the system.

Anyway, it is very hard to tell a marginal synchro visually while assembled, so even to reverse the synchro wear surface you have to disassemble the entire mainshaft-- that fact and the parts cost is why service on these boxes is so pricey- it takes hours.

If it was me and new synchros were not an option, I would turn all 4 around. Would be better to replace at least #2 & #1, and turn 3&4 around or leave 3&4 alone if known to work perfectly. Just be careful not to break anything while disassembling, as you have discovered all these little bits are pricey!

Yeah, I'd try Swepco or Redline MTL/Redline 75W90 cut 50% with a name brand 90W. If it doesn't shift ok with those fluids it has a mechanical problem that gear lube won't fix. j

[jarhead]

Car shifted fine. No issues. It just popped out of second gear while decelerating. I’m just going to replace the countershaft and call it a day. I really don’t want to dig into that main gear cluster. I’ll screw it up I’m sure.

[JT68]

ok, if it shifted fine, I would do exactly what you are proposing.

If it still pops out of gear then counter gear issue was not causing disengagement, and it is a fork or a synchro coupler most likely.

A fork is not too hard to change, but may/may not fix it//

A synchro coupler means tearing down the whole mainshaft

Not low cost parts either.

At least by fixing the counter gear you have probably prevented catastrophic destruction of the 4-sp. If it still pops out and you go back in to fix it later, there probably won't be much more trama -or- start collecting the parts to swap to 5sp.

Before you put the 4sp back in, you could also make sure the 3/4 detent ball spring is not broken and maybe put a single flat washer behind it to provide a wee bit more tension. Trivial to do while the trans is out and very low cost. Worth a try&no harm. best, jt