5 speed vs. 3.9 diff - either or both?

[Boink]

Nice photo, Gerard. Thanks. Good to know where everything is. Nice solution as well.
Jim, I think it's hitting at 12:00 (and the hole in the photo is at that spot - well, I think it is). All installation instructions suggest holding the tail end of the tranny as far over as possible (though there isn't a lot of wiggle-waggle room).
One thing is certain, even if you have to pull up that sheet-metal a little, it's really not enough to notice.

 

[Boink]

PROMISED WRAP-UP (or nearly so):
With the full project complete (a month or two ago), here are a few observations related to performance. First, as a reference point, I have a 1275 engine and now have a Datsun 5 speed transmission (and Datsun clutch) WITH a 3.9 differential (which is the combination that started this lengthy thread). Thanks, too, for everyone's input along the way.

The gains:
a) syncho into first gear (more useful than I thought it would be)
b) beefy Datsun clutch (assembly and disk) with far superior throw-out bearing
c) tight, and many say "bullet-proof", transmission
d) quieter operation
e) much lower revs at high speeds (3.9 diff using the overdrive 5th gear) - though the 3.9 diff probably made the biggest difference in this regard
f) nice safety lock-out feature making it impossible to downshift from 5th into reverse (no biggie)
g) really accurate speedometer readings... and I don't know if this 90 degree adapter is a one-to-one thing
h) everything looks the same (unless you crawl under the car)


The shifting definitely feels different, but that was expected. It's "tight" and the throw seems shorter (especially from neutral to first). Also the clutch has an even and somewhat stiffer pedal feel throughout its range (and works very well with the 3/4" master that allows for more feathering - I'm told that sticking with the 7/8" MC makes the pedal depression very much stiffer and with more of a on/off action). The shifter boot has presented with the predicted difficulties (i.e., even with some glue it just doesn't want to stay put); I may widen the opening and go with the big-Healey boot afterall.

Starting definitely sounds different with the gear-reduction starter.

So, what sort of readings do I see? Unfortunately, my tach cable broke just before taking measurements. However, I can report that the speedeometer is nearly SPOT ON (checked using the GPS app on my phone); it was amazing - probably accurate to within a mile or two per hour (up to 45mph - didn't go faster today)! I'll report back on revs when I fix the tach issue. Anyway, driving at highway speeds now seems effortless.

As others have written, I wouldn't go back to the original tranny and diff.

***************************
COST: well now, this depends entirely on the sources of parts and labor (should one choose to use a shop).
As I originally reported, I was EXTREMELY fortunate to get a Paul Asgiersson (formerly "Morris Services") conversion kit from a old friend for what I think was nearly nothing (and this would be essentially the same kit that Gerard now offers - which I believe to be superior to others). I don't know what a conversion kit currently goes for, but I suspect you can quickly get to $1400+ (if you make related changes). Then, these 1979-1982 Datsun 210 transmissions (also known as B310s with the number "60" on the side - see Gerard's page for proper identification of such trannies) are getting harder and harder to find; again, I was lucky to get a re-built one for almost nothing. Some find a Datsun 210 and remove the tranny only to dispose of the rest of the car (though one might get something for the Datsun A15 engine)! Although these 210 transmissions used to cost $200, they can now run $1500 rebuilt. The 3.9 diff isn't difficult to find (and if purchased might run $300?). So, a complete set of parts would surely run $2,500+, but probably pushing $3,000 depending on tranny cost. Still, doing it yourself, this is a heck of an improvement for the price.
Then, IF YOU CHOSE to have someone do the work, you might be looking at maybe $1500+ in labor... but this would be extremely variable depending shop hourly rate and upon issues that pop up (as they usually do), so I'd give a range of $1500-2000+ for that work. It's not a difficult thing to do oneself, but there can be a fair bit of fettling upon putting it all back together. The biggest part is just pulling and reinstalling the drive-train.
So, parts and LABOR could run about $4500 (as low as $4000 and as high as $6500)?

P.S. - there can be ancilliary costs in the form of upgrading to a 3/4" master cylinder system if one doesn't already have that for disc brakes (which, again, Gerard offers); while a 3/4" is better for discs, it makes the clutch action much better (both in lessening pedal pressure required and creating a better/gradual action). Some take advantage of the opporunity to replace the engine rear oil seal (with a better one - and easy to do with the back-plate off). Some may opt to have a shifter made or modifications to the shifter housing. This is why it's impossible to say one price will fit all.

 

[Pythias]

If there's no hurry, wait until the end of April. I'll have the red thing at the All British Swop Meet (for sale). It's got the 3.9, 5 speed and 1275. Take it for a test drive and see if you like the combination.

 

[Boink]

If there's no hurry, wait until the end of April. I'll have the red thing at the All British Swap Meet (for sale). It's got the 3.9, 5 speed and 1275. Take it for a test drive and see if you like the combination.

There you go. Hope you can sell the car at the Swap Meet, Bill. I won't be able to make it this year (as I'll be in Italy at that time). But I sure can now attest to the combination.

 

[Gerard]

This has been sorted out quite successfully with the quick shift kit I have developed. Pictured is a crude prototype, which you can see not only has a dramatically reduced stroke (a 50% reduction) but also the original turret and rubber gaiter can be used without modification. Even though my prototype/proof of concept is a bit off center (something that will be corrected in the final product) it still worked flawlessly - no binding or inclination to pop out.

Everything is in the hands of the machinist (same guys that make many of the 5 speed components and seal kit), and I expect a finished product in the next couple weeks.

PROMISED WRAP-UP (or nearly so):

The shifter boot has presented with the predicted difficulties (i.e., even with some glue it just doesn't want to stay put); I may widen the opening and go with the big-Healey boot afterall.

 

[Boink]

Excellent, Gerard. I'm not sure how it's done, but it sure looks good.
My stick comes out at, essentially, the same angle... but I wonder if my offset shouldn't have been a tad further to the right.
My boot is currently set-up as an "outie" not an "inie." I wonder if that matters too.

 

[twas_brillig]

Mark - I'm about 4 months late, but could you advise as to the rough inch dimensions of the 'needed' hole in your photos from last November, and how far 'down' from the engine mounting face to start? I'm getting another engine and Datsun 5 speed, and will want to make this modification. No panic if info not available as your photos (thanks again!) provide a good reference; the Silver Sprite currently has a 1275/5 speed in it, and I'll mark up the housing with the location of the front edge of the heater box assembly before pulling, and add a few inches (or feet...). Thanks, Doug.

 

[twas_brillig]

FY: Differential and gear ratios

Differential	4.22​	Original BE
Differential	3.9​
Differential	3.73​	AH Spares lists a 3.7
	​
	​
1st gear:	3.62​	Smooth case
	3.2​	Rib case
	3.513​	Datsun
	​
Top gear	1​	Sprite (4th gear)
	0.821​	Datsun (5th gear)

 

[Boink]

Doug, are you referring to the cut in the bell-housing on the Datsun transmission (so-as to clear the heater-box tray/shelf)? I didn't otherwise make any modifications to the car itself.

 

[twas_brillig]

Yes - the bellhousing cut (first photo, page 3 of this thread, posted Nov. 13/16). We had a bug-bear of a time fitting the engine/trans without this modification (ended up removing the crankshaft pulley and then reinstalling it after clearing the frame, and even that still required a bunch of grunting, groaning, and imprecations). Thanks, Doug

 

[Boink]

Right, that cut-out of the bell-housing is really rather essential. I'd not remove the harmonic balancer OR the front steering rack, but even with the bell-housing cut-out, the fit is EXTREMELY close (i.e., a millimeter clearance at the heater/battery shelf - some even beat the tray upward, but I didn't want to make that mess). Besides without the cut-out you'd have to remove the steering rack just to get it all back out. Let me go back and look at what I have for information in this regard... and then I'll edit this post.

EDIT: OK, a couple of things. First, do recall that I received a 5 speed that was already cut out and patched, and the cut-out was actually much larger than needed. Gerard was concerned that the flywheel or clutch might hit the new patch, but, thankfully it didn't (though to play it safe I did pound the patch out a little). The original patch that I received (with the joke label on it) is in this photo. This patch goes up too high on the case and probably dives in a bit too deep, but it worked
So, then, I had the luxury of looking at Gary H.'s tranny (on this forum and has posted in this thread) in person. He had pulled it out to replace his engine. In that photo from earlier in this thread, he made a very nice patch (which I edited here). These numbers I've added are ball-park dimensions but, frankly, I don't think it's all that critical. My larger cut-out might have made the install easier, but Gary said he got this one back in his Sprite OK. The patch is just a lightweight sheet metal (rolled a bit if possible).
Of course, there is another cut-out that you may need. That other cut-out is for the stem of the starter motor. I didn't have to do that because I used a gear-reduction starter which doesn't require it. I do have photos of Gary's nice work at cutting out a hole for the starter (which, optimally, requires a metal cover).

 

[twas_brillig]

Thanks - that second photo is all that I needed. We'll try to get the Silver Sprite completed and roadworthy with the current installed power-train, but an aged Brit is assembling a 1275/5 speed combination using a Paul Asgeirson kit that he had in old stock. When it's ready to go, we'll go down to the river and grab a beaver with stellited teeth and turn him loose with your picture. We kept the original starter (and carved a hole for it) in our Yellow BE, but the Silver BE has the gear reduction starter and we'll transfer it over when 'new' engine etc. is available and installed.
Thanks again! Doug

 

[twas_brillig]

Here's a comparison, showing the axle rpm for different transmission and differential combinations, plus also the car's speed (km/hr and mph) assuming an arbitrary engine rpm of 4000 (and that the engine has enough power to achieve the speed). The km/hr - mph ratio was taken from a Spridget web-page (see https://www.automobile-catalog.com/auta_details1.php ) that advised 25.4 km/hr and 15.8 mph per 1000 rpm for a stock 1965 Sprite Mk III with a smooth case transmission, 4.22 differential, and stock 5.20 x 13 tyres. And - hopefully - no errors in the arithmetic. Please note that my numbers are consistently 5% higher than Gerard's earlier in this thread, so the tyre sizes/ratio/whatever that I used may not be perfect.


.

							Engine rpm​
1000 Engine RPM yields:			Speed at 4000 rpm:		100 km/hr​
Axle RPM:	Description​	Change		Km/hr​	Mph​		62.1 mph​
				​	​	​
237​	Stock: 4.22, 4 spd., top gear​			102​	63​	​	3937​
289​	4.22 diff with Datsun 5 spd​	21.8%​	​	124​	77​	​	3232​
256​	3.9 diff, 4 spd, top gear​	8.2%​	​	110​	68​	​	3638​
312​	3.9 diff with Datsun 5 spd​	31.8%​	​	134​	83​	​	2987​
268​	3.73 diff, 4 spd, top gear​	13.1%​	​	115​	72​	​	3480​
327​	3.73 diff with Datsun 5 spd​	37.8%​	​	140​	87​	​	2857​

Doug

 

[Boink]

Nice table, Doug. Thanks!
If you have the Asgiersson kit, a 3.9 diff AND the 90 degree attachment for the speedometer cable, you might be surprised at how accurate your speedo will be. I still can't quite get over how well it all works (though I'm told that Paul really worked to get that right).

 

[Gerard]

When you ordered a kit from Paul, you would submit which speedometer, tire size and diff ratio you had on the vehicle you were installing the ket. He then geared the angle drive accordingly. If your speed is close to being accurate, you have the same setup as whoever he originally sold it, and you just lucked out. There were seldom two the same.

Nice table, Doug. Thanks!
If you have the Asgiersson kit, a 3.9 diff AND the 90 degree attachment for the speedometer cable, you might be surprised at how accurate your speedo will be. I still can't quite get over how well it all works (though I'm told that Paul really worked to get that right).

View attachment 47813

 

[Boink]

Ah, makes sense because I also found a slip of paper with various numbers on it (related to the speedo). Pure coincidence that although I think all this was set up for a Morris Minor, it all worked perfectly with my Sprite. Ratios and tires might have been pretty close. Lucky me. :rolleye:

 

[Boink]

Found the note that came with this kit... which, it turns out, WAS going to be used in a Bugeye and not a Morris Minor like I thought (but that Bugeye received a Toyota engine/tranny). Anyway, my tires are P175/70R13 ones (certainly much larger than original Bugeye tires), so although I don't know my speedo number, I really did luck out. What Paul made works beautifully.

Went to https://www.tacomaworld.com/tirecalc?tires=175-70r13-165-70r13 and found that with my tires, my speedo could be off by just 2% (which seems like nothing). Very nice calculator by the way.

 

[Pythias]

Paul used a Speedo Shop in Portland. Interestingly, he used various shops all over town for different parts for his kit. No one place knew all of what he was doing, kind of like the way the KFC recipe it sourced all over the place and only one or two people know the whole of it. I believe it was for the same reason; that no one could then duplicate his kit. Either that or he had found the best place to source each component. ...

I remember when the electrical supply houses in town stopped carrying KINDORF strut that he used as a rear bracket on the tranny. Everyone had stopped and was now carrying, UNISTRUT. Well, Unistrut is 7/8" and Kindorf is marginally smaller. Nominally 7/8, but he showed me with a micrometer that it was thousandths different. He was now going to have to buy Unistrut and take a pass with a grinder to make his kits....

 

[Boink]

Paul used a Speedo Shop in Portland. Interestingly, he used various shops all over town for different parts for his kit. No one place knew all of what he was doing, kind of like the way the KFC recipe it sourced all over the place and only one or two people know the whole of it. I believe it was for the same reason; that no one could then duplicate his kit. Either that or he had found the best place to source each component. ...
I remember when the electrical supply houses in town stopped carrying KINDORF strut that he used as a rear bracket on the tranny. Everyone had stopped and was now carrying, UNISTRUT. Well, Unistrut is 7/8" and Kindorf is marginally smaller. Nominally 7/8, but he showed me with a micrometer that it was thousandths different. He was now going to have to buy Unistrut and take a pass with a grinder to make his kits....

Yes, Paul had a bit of secretive side in this regard. Can't blame him. I believe he used "Speedometer Services" in Portland (a shop I've also used before - good people). Still, it wouldn't surprise me that he used multiple sources given all the parts. He used a few different shops even to machine the flywheels.

 

[Gerard]

You can't even begin to imagine how many different resources and suppliers it requires to put a kit like this together. I do both the Spridget and Morris kits, each of which have unique components. It may not seem like it when it arrives in a nice tidy turnkey package, but almost no two items come from the same place. Almost nothing is available locally and local resources I did have, evaporated over the last year. After my next batch is gone, I will either stop making these entirely or make it a much pared down DIY kit where the buyer will have to source or fabricate the other bits on their own.