Transmission gear ratios

[Rut]

I have several transmissions and don't quite understand what the different ratios are. Could someone please enlighten me?
1 smooth case
2 rib case
3 rib case SCCR
4 Datsun 5 speed
I also have 4.22 and 3.9 rear ends and I'm going to use the car for general driving on weekends, no extended highway trips. What would be the best overall choice and/or combination?
Thanks, Rut

 

[Trevor Jessie]

My choice would be datsun 5-speed and 3.9

For casual driving you get that syncronized first gear, and at 55 mph in 5th gear you will be around 2700 rpm.

Of course, I'm biased because this is how both of my cars are setup.

 

[Pythias]

Of course, I'm biased because this is how both of my cars are setup.

That's not bias, it knowledge and experience.


Mine is set up the same way, but with a 1098.

 

[bug_sixty]

vote for 5 speed for no other reason than syncro in 1st.. a biggie driving around with stop and go and those "have to stops" hills with the nonsync's for instints is huge... the other stuff is subjective for you probably...then again it might some day save a ticket for not making a complete stop at a light! We have red light camera's up here and they dooo...

 

[RickB]

I have several transmissions and don't quite understand what the different ratios are. Could someone please enlighten me?
1 smooth case
2 rib case
3 rib case SCCR
4 Datsun 5 speed
I also have 4.22 and 3.9 rear ends and I'm going to use the car for general driving on weekends, no extended highway trips. What would be the best overall choice and/or combination?
Thanks, Rut

Please define "general driving".

For one person that might mean some meandering drives around corners of the favorite little roads out in the countryside.
For others it might mean they like to drive it like they stole it.

Trevor's spot on, unless you will be spending much time above 65 MPH. For the 70 - 85 MPH crowd the 5 speed and 3.7 is really nice.
Now I just have to make sure the State Patrol doesn't see my drives to work... Those new wheels and tires make my car a real pleasure cruiser at 80!!

 

[bug_sixty]

ah SP wouldn't believe their lasers... That little blip on the road doing 80 naw, gun must of picked up something else...Then again, they might be curious just to see WHO would even risk their fannies sitting a foot off the pavement... hint..it ain't some crazed teen on drugs..haha

 

[Rut]

RickB,
Most of the time I'll putt around with my wife on weekends, but I do like to run it hard when alone. I may even get back into auto x if I can find one close to me. I doubt that I'll get on the interstates, but we have a lot of country roads that are 'posted' from 45 to 65 that are virtually copless. Let's define general driving as 'spirited'.
Thanks, Rut

 

[RickB]

RickB,
Most of the time I'll putt around with my wife on weekends, but I do like to run it hard when alone. I may even get back into auto x if I can find one close to me. I doubt that I'll get on the interstates, but we have a lot of country roads that are 'posted' from 45 to 65 that are virtually copless. Let's define general driving as 'spirited'.
Thanks, Rut

Then I'd go with a 1275, rib case and 3.9 diff.
"As God Himself intended it to be"

I honestly think that combination would be best for the "general" type of driving you describe.

 

[smaceng]

I first built up my BE with the mild 1275, 3.9 and the ribcase. It was really a pain to drive on the highway, as it would cruise happily at 4,000 rpm, but that was about 60 mph. I now have the Datsun 5-speed, and it makes all the difference in the world. It is much more enjoyable at speed, and having the more usable Ist gear is a real treat!
Scott in CA

 

[RickB]

I agree Scott, spending much time on the freeway with a 5 speed is a game changer.
Not spending much time on the freeway however would make the 5th gear overdrive a bit of a waste, as it really provides it's main benefit over 60MPH.
The 1st gear syncro is of course the other big benefit, but I don't know if it would be enough by itself as you could get a 60 series 4 speed and have the 1st gear advantage.

IMHO - of course!

 

[Gundy]

It all depends on your needs. Personally I love the 4.22 with
a sc/cr box.
Tried a 3.7....made my car a slug..and I'm running a 1380cc.
I love the close ratio tranny. Most of my driving is done on
mountain twisties and for THAT the 4.22 and the sc/cr box ROCK.
Noisy...high 1st...but boy o boy it is a weapon on a mountain road or at a track.

That and it keeps the ol girl all Brit...just not how it came
from the factory.
The Datsun 5 speed and a 3.9 or 3.7 would be ideal for most
needs and is a performance upgrade for sure.
Bonus for a 5 speed is you can FINALLY fix that rear scroll leak.

 

[The_architect]

Okay, for the uninitiated, what does sccr mean, and how do I know if I have one? :frown: Charlie

 

[reddsprite]

Straight Cut Close Ratio-you will definitely know if you have one

 

[mightymidget]

https://www.wallaceracing.com/gear-speed.php

If you have some time and really want to have some fun

 

[Gundy]

Okay, for the uninitiated, what does sccr mean, and how do I know if I have one? :frown: Charlie

SC/CR tranny is a racing box. Straight Cut, Close Ratio.
Lots of noise. Sounds like a bad tranny.

The ratios are grouped close together to allow you to
maintain the engine in it's "sweet spot" a bit easier.
Several places to buy the gears or a complete tranny
exist.
Here is Minimania's version.
https://www.spridgetmania.com/web/Item/C-AJJ3319/InvDetail.cfm

 

[BuggerAll]

Cheapest source (for gearsets) is direct from Minispares in the UK - $ is up against the pound, too -

 

[Spridget64SC]

Straight cut gears will look just like the name implies. The gear tooth will be cut straight across. Helical gears (stock type) have a curve to them. The curve helps with the noise issue. If you open the side cover of the gearbox and look at the gears on the mainshaft, you will see what you have. Starting from the left side of the main case, you will see the 1st/2nd/Reverse slide gear. It is cut with straight teeth whether SCCR or Stock gearbox. Reverse will be below it and will also be cut with straight teeth. 1st & reverse are noisy. Moving forward, 2nd gear is the next one you see. Then 3rd gear. Between 3rd and the back of the input gear/4th is the 3/4 slide gear. It has no external gear teeth. All it's teeth are on the inside and connect either 3rd or 4th depending up which way it is engaged. The input gear is the last one on the right. The small teeth are what 4th gear is. 4th is a 1 to 1 connection and engine rpm is transmission output to the driveshaft and the differential. The actual gear teeth you see at the front of the main case behind the input shaft bearing perform the "drop" function to drive the laygear and create 1st/2nd/3rd gears as well as reverse.

This is more information that you wanted regarding the difference between straight cut teeth and helical cut teeth, but helps understand the general arrangement of the gearbox. With a SCCR kit, you get a new input, new laygear, new 2nd and new 3rd. The other gearbox parts stay the same and get reused if in good condition.

FWIW, MiniSpares just got a supply of SCCR pieces and is restocked with kits. The Spridgets and older Mini's share most of the SCCR kit pieces with only the input shaft being different in the kit.

HTH,
Mike Miller

 

[Boink]

Not much to add but:

 

[The_architect]

Oh so I do have a SCCR box. Too bad it is in my Ford 9N tractor.