Assessing Manual Transmission Condition

[Randalla]

I'm swapping out my wide ratio 5-speed for a close ratio transmission. I'm curious to know what, if anything, I can tell about the condition of the replacement transmission prior to installing it. I'll have a choice between a number of loose transmissions and obviously want to make the best choice I can.

[SoCalJim]

Great topic, Randalla.  I have a close ratio 5-speed that I bought a while back for eventual use in my ‘75 280Z.  It’s clean on the outside, but unknown to me on the inside.  I look forward to the feedback you receive from the folks on this forum.  ?

[Dave WM]

Other than do they go into all gears, not much. Could try to spin them in gear and listen for weird noises. I hooked up a high speed drill to a rubber hose that fit tightly over the input shaft, then a bolt into the other end, chucked into the drill. the hose acted as a flex coupling. You could remove the drain plug and look at the metal particles that will be stuck to the magnet (if not already cleaned off). Look for chucks (bad) fine particles not a big deal. You are looking for bearing cage bits etc..

The only real way would be to open the case up and examine the gears for broken teeth or other obvious damage. You could prob check the end play and baulk rings wear with some feeler gages.

As a minimum plan to at least replace the seals on the input and output shaft. that can be done without separating the cases.

 

 

Edited August 27, 2019 by Dave WM

[wheee!]

I am doing the same thing basically. I cleaned up my five speed and replaced the seals at both ends. It shifts smoothly and seems solid and the previous owner removed it to add a BW tranny even though the original was working fine.
Everyone seems to think the original parts are stronger/more reliable than the ones available in rebuild kits. I was advised to run it as is until there is a reason to open it and replace the OEM parts inside.

Edited August 27, 2019 by wheee!

[Randalla]

Really great feedback guys. You've given me at least a few things to check to determine which one to choose. I've installed two or three 5-speeds in the past without checking or rebuilding them and have had pretty good luck. Your suggestions will at least give me a few ways to discriminate between three different transmissions I'm looking at. I've also heard the original internal parts are more robust than the rebuilds. Worse case is I have to eventually take it out and send it out for a rebuild. Thanks again. On a related note, how hard is it to rebuild a Datsun manual transmission for a fairly handy guy who just has never tackled one? Are there quite a few specialized tools needed? I have a number of junk 4-speeds to practice on.  

[Dave WM]

having a press helps a lot with that and a bearing puller set and an assortment of steel pipe connectors (the kind used in plumbing to make fixtures) its really pretty easy. On a Torx driver is needed as well, and a SOLID snap ring remover tool is a must. I used a wood dowel to store the gears and hubs to keep everything in order. One last thing there are a couple steel balls used to lock in some parts, you just have to keep up with them. The actual workings are not that intimidating once you get into it. You have to use some creativity to substitute for the jigs mentioned in the FSM, but that is what the steel pipes are for. The only part that gets tricky is the small parts inside the sychro hubs. If you are careful they can come out with out disturbing those bits. No real need to break them down. I think the main wear items besides the baulk rings is the teeth on the sychro hubs. That's what you hear grinding if the trans is abused. The front counter shaft ball bearing is another part to look at, its a bit smaller than the later transmissions. The reverse idler is often chewed up a bit but that is not a huge deal.

I would think the worst case would be a bent output shaft. That would be worth putting on some v blocks and checking for excessive runout.

 

[Dave WM]

there is a guy on you tube "villageland" that has a nice video, no audio but you will get the idea of what is involved, and he manages to rebuild it without a press.

[AZDatsun]

Make sure it has the reverse lockout port on the tail housing extension so you can easily access the striking rod pin with a punch. you may need to change the o rings that leak.


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[Mark Maras]

 Take a good look at the brass baulk rings. The teeth, when new, are pointed and sharp. The 2nd gear synchro will show the most wear, 3rd gear synchro a bit less. If the 2nd gear synchro looks good the others should be fine, although I have encountered broken baulk rings that looked good except for the crack. I've refreshed a few different transmissions in the past. GM T10s, Ford top loaders, Toyotas, etc. These Datsun transmissions aren't difficult to refresh. A thorough cleaning, new synchros, seals, gaskets and bearings are my usual refresh. I also use a dowel to keep the parts in order. Keeping the parts in order and oriented properly in the cleaning process will save a lot of time and headaches later.

[Dave WM]

I don't know how critical it is, but there is a brass bush on the tail shaft. considering how long that shaft is, I would consider that a replacement item as well. this is what the front of the driveshaft turns in. You can replace it by separating the tail shaft housing only from the center plate. that would be a good time to do both it and the rear seal. If the bush is ok then the seal can be done without taking anything apart. there is a long bushing and a short one, you want the long bushing. On mine the oil catcher that feeds oil back to it was broken off. I knew this cause it was stuck to the magnet. Not sure how else you would know without separating the transmission front half from the bearing plate.

[Randalla]

This is really helpful. It just may give me the confidence to tackle my first one as a trans virgin. Any idea what the rebuild kit costs and where to find one? Here in AZ the cost to have someone else rebuild a Datsun 5-speed is $800-1,000. The challenge would be fun and I'd like to be able to add that to the list of jobs I feel competent to do.   

[Dave WM]

90-150 depending on if you get just the bearings and gaskets or the whole set (balk rings). lots of places sell them, they don't include the needle bearings for the gear clusters, I guess those are not a typical failure point. you get the main ball bearings, gaskets and seals, brass balk rings and the one needle bearing that fits on the input shaft. I would say that unless there is a known issue OR you just want the experience (I fully understand that as well), rebuilding may not be needed. You could just install it, try it, then if not happy pull and rebuild. It takes me about 5 hrs to pull a transmission so its not like a huge investment in time to try it out. A lot of the time for me was just getting the car up high enough and safe enough to crawl around and have room enough to drag it out from under the car.