5 speed questions

SLOroadster · Post by **SLOroadster** » Sat Apr 12, 2008 12:59 am

Its the actual gear its self that you need to look at. I can't tell if you have the later one or not. If you shoot me an email I will try and take some good pictures of my spun 5th (if I can find it) so you can compare. I'm going to guess that its a press fit as there were only about 200 of the 1970 cars that had the later 5th gear. Thats not to say that it couldn't have been replaced at a later date however.

Will

datsunrides · Post by **datsunrides** » Sat Apr 12, 2008 8:58 am

OK, I'll pull the gear off and look at it further.

Mark

datsunrides · Post by **datsunrides** » Sat Apr 12, 2008 11:15 am

Got 5th off the output. Looks to be pressed? Or an I still looking in the wrong spot? This rides on the double needle bearings.

Mark

SLOroadster · Post by **SLOroadster** » Sat Apr 12, 2008 9:49 pm

If you look in the cutout in the gear there, thats how you tell. The inner piece (the part that has the 4 notches cut in it) is the part that slips when it goes. The splined version will have splines that can be seen in the outer portion cutout. They sit pretty far in but you can see them, the nonsplined one is smooth (I think, I can't find what I did with mine, I know its here someplace....)

Will

datsunrides · Post by **datsunrides** » Sun Apr 13, 2008 11:28 am

That's what I thought. Now, it looks like Dean has the best price at about $350. Anyone know a better (less expensive) choice? I will probably just try having the existing gear TIG welded if there is not a less costly source, which leads to the next question- where to weld it and are we talking spot welds, stitch welds or full blown weld all around?

Mark

Eric F · Post by **Eric F** » Sun Apr 13, 2008 1:29 pm

[quote="oilleak"]It's a borg warner (brass) box.
In my opinion don't waste your time with trying to weld the gear - buy a splined one.
No need to weld the main shaft nuts. The double nutted main shaft fixes the issue with the nuts backing off the shaft so long as they're assembled correctly. I don't remember the torque spec for tightening the front most nut against the gear cluster but I think it's 25ft-lbs. After which the jam nut is snugged up behind the main nut and then the important part is that the main nut is backed off against the jam nut at 225ft-lbs.
It won't budge after that.
[/quote]

I disagree on both counts. First off, the double nutted crap system does NOT work as advertised. My tranny shop followed the directions exactly and the nuts worked themselves free after probably 2000 miles. Tack weld them and you should have no worries.

2nd.. welding the 5th gear. If you are racing or driving extremely hard, then perhaps it would be a good investment to buy the splined version. Otherwise, get it welded! Mine was done beautifully for $30 and the car now has over 25K on it... NO problems and the tranny shifts like it was brand new.

Eric F · Post by **Eric F** » Sun Apr 13, 2008 1:31 pm

Eric F wrote:
oilleak wrote:It's a borg warner (brass) box.
In my opinion don't waste your time with trying to weld the gear - buy a splined one.
No need to weld the main shaft nuts. The double nutted main shaft fixes the issue with the nuts backing off the shaft so long as they're assembled correctly. I don't remember the torque spec for tightening the front most nut against the gear cluster but I think it's 25ft-lbs. After which the jam nut is snugged up behind the main nut and then the important part is that the main nut is backed off against the jam nut at 225ft-lbs.
It won't budge after that.
I disagree on both counts. First off, the double nutted crap system does NOT work as advertised. My tranny shop followed the directions exactly and the nuts worked themselves free after probably 2000 miles. Tack weld them and you should have no worries.

2nd.. welding the 5th gear. If you are racing or driving extremely hard, then perhaps it would be a good investment to buy the splined version. Otherwise, get it welded! Mine was done beautifully for $30 and the car now has over 25K on it... NO problems and the tranny shifts like it was brand new.

SLOroadster · Post by **SLOroadster** » Sun Apr 13, 2008 2:44 pm

Feel free to disagree with me but I have never had issues with the main shaft nuts comming loose. I'd say don't weld them. Knowing the Hp thats going to be put through that transmission, and the fact that if it gets driven it will be in 5th most of the time, spend the $$$ for the splined one. You will be making far more Hp than I do, and I've nuked 2 non splined and one welded 5th. On the track I think my car has only seen 5th perhaps a handfull of times. Its the 49000 miles of freeway driving sitting at 5K that nukes 5th gears. In my case I'm basicly sitting on 90% peak torque and that seems to be the killer of 5th gears.
The first time my gearbox was opened up the mainshaft nuts were good. The second time it was opened up they were still good, I hope it won't be opened again anytime soon.

Just my $0.02

Will

RC240z · Post by **RC240z** » Sun Apr 13, 2008 7:53 pm

Spyder, I see that you do not agree with me and your are welcome to think what ever you want. I would say running a Datsun gearbox for 20+ minutes at a shot up and down through the gears as hard and fast as possible is much harder that spirited driving or aoutcrossing.

Since I don't run a stock transmission, rather an ultra close roadster box there are plenty of differences. Also I run different rearends that, depending on the track will give us more power out of the turns. We build our transmissions to race and have 40 years of experience with the guy that builds my racing Datsun transmissions. All I know is that my stuff holds up because it is done right, and we treat it right.

Breaking this stuff is an expensive indeavor as replacement parts are harder and harder to find.

What is right? Well that seems to be quite different depending on who you ask on this forum. We weld 5th gear (and we don't pay $350 bucks for them)!! and we do not weld the jam nuts together. Because a transmission has to be servicable.

Post by **spl310** » Sun Apr 13, 2008 8:00 pm

RC240z wrote: we do not weld the jam nuts together. Because a transmission has to be servicable.

AMEN to that!

datsunrides · Post by **datsunrides** » Sun Apr 13, 2008 8:56 pm

So anyone have a pic of a welded 5th? I will go this route and see what happens. I don't have an issue with pulling the trans and putting in a splined 5th should the weld break. I can't see the weld breaking if done properly with a little preheat beforehand. I might be running a little more power than a stock U20

, but I don't see too many circumstances that will have me in 5th under full boost. If it does fail, all it's costing me is time. I can do all the other work myself. At some point in my life, I'd like to stop throwing money into this like a reverse ATM and actually drive it, especially the way the economy is looking. Right now, I have better uses for the $350 than a gear. While having no firsthand experience of the nuts backing off, I can say the locking nut on this puppy was tight as h*ll. I will just make sure it's torqued to spec and let it ride.

fj20spl311 · Post by **fj20spl311** » Sun Apr 13, 2008 11:43 pm

datsunrides wrote:So anyone have a pic of a welded 5th?

Sorry I don't have a picture, but drop buy one of the local BUGGY Shops and they should have a welded gear for sale for a VW trans. The procedure is the same for the Datsun.

oilleak · Post by **oilleak** » Mon Apr 14, 2008 9:04 am

[quote="Eric FI disagree on both counts. First off, the double nutted crap system does NOT work as advertised. My tranny shop followed the directions exactly and the nuts worked themselves free after probably 2000 miles. Tack weld them and you should have no worries.
quote]

You can disagree all you want but mines been fine for fifteen years now. Your shop didn't do it right. I did mine myself so I know if was done right.

As far as the price of the gear, you just need to determine what costs more, the gear or your time. My time is worth more than the money I'd save skimping.

Eric F · Post by **Eric F** » Mon Apr 14, 2008 2:50 pm

Sorry, I didn't take a picture of my welded 5th gear and I regret that daily! Basically, they preheated, then ran a continuious TIG bead around it. It was really a thing of beauty and after it was all said and done, the gear didn't require machining. As for the double nuts, it was a very small tack weld once they were properly torqued against each other... nothing that would destroy the integrity of the nuts or be too difficult to lightly grind away in the event of needed repairs.

Question though... who the heck is using 5th gear at full power anyway? It's listed as an overdrive gear on the original Datsun 2000 manual, as well as just about every other manual I have seen. I know most good autocrossers don't ever get up beyond 3rd gear mostly, but am not sure about the other racers?

Eric F · Post by **Eric F** » Mon Apr 14, 2008 3:04 pm

oilleak wrote:[

Each to their own, Brian. That's the beauty of sharing ideas and experiences on this forum. You are correct, spent the extra money and have 15 years of success to prove it. I am correct, spent less and have 25K+ miles to prove it. No matter what happens, I hope that Mark is able to get his car back together with all the combined knowledge and experience this forum is able to provide him!