U20 Transmission Swap

[Steve49841]

I'm wondering what you guys think is the best replacement choice for the stock 5Spd in a race car. I have searched around and can't find a discussion on the subject. The current box is getting tired, and won't last forever so I'm going to have to do something at some point. Ease on installation is a consideration but strength and shift quality is at the top of the list.

[Skyman]

Is having it rebuild not an option?

[dbrick]

Search here for "diesel Transmission", nice modern box

[fj20spl311]

There are some who advise against an Overdrive 5th gear because the drive shaft speed is too high.

What do your rules allow?

What is your budget?

[Steve49841]

Thanks for the replies. Do you guys know a shop that has a good reputation for rebuilding Datsun 5pds? I guess that would be the most direct route if it would make the current transmission shift properly. Rules?.....what stinking rules... the transmission can be anything as long as it's a 5spd. Most vintage organizations make a token effort to insure originality, obvious things like correct motor, no wings and some kind of treaded tire but that's about it. And as for budget, I suppose a $20K sequential box might be a little over the top but what do you have in mind.

[jamesw]

I know that Les has a guy that rebuilds the Roadster 5-speeds and previous customers are happy w/ the work. You can ship it to him in a rubbermaid tub surrounded by those expanding foam baggies.

HTH
James

[Steve49841]

Are we talking about Les Cannaday?

[Gregs672000]

Are we talking about Les Cannaday?

Yes. Wow, shortest answer to a Roadster question I have ever done... so I had to say that just to make it worth reading!

Nobody on the East coast area that is knowledgeable about these boxes? Gotta be someone...

[dbrick]

And as for budget, I suppose a $20K sequential box might be a little over the top but what do you have in mind.

Give me 15K for my spare 5 speed, 25% savings:D
Seriously, do you use 5th gear and is a street ratio box useable? If a close or ultra close is better suited to the tracks you run, then a Roadster box may be the only choice, as there are semi-available options.

[SLOroadster]

And as for budget, I suppose a $20K sequential box might be a little over the top but what do you have in mind.

Give me 15K for my spare 5 speed, 25% savings:D
Seriously, do you use 5th gear and is a street ratio box useable? If a close or ultra close is better suited to the tracks you run, then a Roadster box may be the only choice, as there are semi-available options.

I've used 5th on two tracks out here on the west coast, Buttonwillow in the configuration that has the longest possible back side, and Thunderhill. I don't know if any of the east coast tracks have a long enough straight. T-Hill and Buttonwillow have really long straights (Buttonwillow actually has a bend in it but its so gradual that it might as well be a straight, you don't lift for it.) The stock 5 speed is ok, but a mid close or ultra close box is better suited for race use. They keep the engine in the powerband better and depending on the track, keeps you from making lateral shifts (as in a 2-3 shift, it would likely be a 3-4 shift with one of the comp boxes. )

Running a short rear end, 5th will be a useable gear. Depending on what gear box it is, (mid/ultra close or direct drive 5th) everything gets pushed together into essentially the same space as 2,3,4 but with the DD5th, I think 5th gear becomes a 1:1 ratio (don't quote me on that) Still, 1st is almost where 2nd on the stock box is, and then everything after that gets stuffed into the remaining space between 2nd and 4th (still a 1:1), 5th is still the same. (sorry that is poorly worded, but hopefully you get the idea.)

There has to be someone on the east coast who can do the box. I'd get ahold of Bill Wessel (GP Datsun is his screen name I think) , I'd bet he knows someone.

Will

[Steve49841]

There probably is someone in the East that can do it but I'm on the southern shore of Lake superior so it's shipping no matter what I do. I think Bill Wessel is running a Quaife transmission in his car but if anyone is rebuilding a Datsun 5spds in the Midwest he will know who it is. So in all of this it sounds like there is no bolt in up grade transmission for race cars which leaves me with the rebuild route. I'm okay with that if it gets me away from the double clutching, grinding missed down shift situation I have now. And about using 5th gear, we have Road America with its long up hill straight so 5th comes into play there.

[Gregs672000]

It's my understanding that this was an excellent shifting box for its time, so once properly rebuilt I think you will be quite pleased. Be sure to have the rebuilder address the since discovered weaknesses. Good luck on your racing campaign, and return here for encouragement!

[SLOroadster]

It's my understanding that this was an excellent shifting box for its time, so once properly rebuilt I think you will be quite pleased. Be sure to have the rebuilder address the since discovered weaknesses. Good luck on your racing campaign, and return here for encouragement!

I must say a freshly rebuilt roadster box is the most smooth shifting transmission I have ever come across. Heck, mine is starting to get tired and is still smoother than anything else I have driven. Far smoother than any L series box. I do have to say the 5 spd Skyline transmission (as in Hakosuka) is very close however. It doesn't feel like an L series box, but I'm not sure what it actually is.

Will

[mraitch]

I recall a quote from Sir Stirling Moss - 'the roadster box will shift as fast as you can make it' - or something like that. That's praise indeed.

[gpdatsun]

Hello Steve,

No I don't know anyone to rebuild the 5-speed, other than yourself. I have taken them apart and assembled them again. You need strong snapring pliers, a bench vise with softjaws and a good manual and parts diagram (which are readily available). But I also had reliability problems with the UC 5-speed box, so I looked around for something more beefy.

I now use a Quaife ultra-close Rocket box 4-speed, which set me back $5k many years ago, the single most expensive purchase other than the actual car. See Scotty and Dan at Taylor Race Engineering. I went with the 4-speed, because Col Joe before me didn't like to overspeed the driveshaft (the trans tailshaft case was a weakpoint, but if you reverse the driveshaft, it's less prone to breaking) and the modified rear allowed easy pumpkin changes without breaking brake lines. So I continue to change rear gears to suit the track (4.63 for short and 4.38 for long).

But with a 5-speed , you can get away with a 4.63 and be set for most all tracks (as long as 5th is overdrive).

Weakness in the stock box was with the shift forks breaking and/or the roll pins that secured them. The roll pins are long NLA from Nissan comp but are available through web search (I obtained a minimum order of 50 or 100 many years back and distributed them to other racers at the time).

Bill