• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

5 speed vs. 3.9 diff - either or both?

Share this page

Paul used the clutch slave from the Sprite tranny when he did my conversion....

I LOVE the 3.9 with the 5 speed... I never notice that it's sluggish off the line and it cruises wonderfully.
 
Hey Bill.
I probably should have looked more carefully at yours too at the last ABFM. LOL
I've seen the adaptor for the slave unit (as well as ones for a Datsun).
 
OK I think I can weigh in on this as I can compare my old '68 Sprite Bugsy I with a 4.22 Pumpkin to driving Bill Mayer's 60FROG with a 3.9 rear and a 5-Speed.
1) First and foremost, Synchro First Gear. Year, a usable First Gear that transforms the car.

2) First Gear with a Datsun 5 Speed is a lower gear ratio that a Ribcase 4 Speed. You will find that you will run out of first gear faster and need to shift sooner without the 3.9 Pumpkin

3) I noticed very little perceived performance difference in 1st Gear in fact I think it was enhanced with better matched tranny and read end ratios.

4) The real beauty is simply being able to stay with Modern Traffic. Bugsy I in spite of rebuilt shocks, rebuilt front end, all new bushings was really pushing to get over 60, 65 a bit scarier, and 70 engine absolutely screaming and it felt uncomfortable to go there even on a smooth expressway you were fighting to maintain any sort of speed. Now that engine was quite worn and definitely needed a rebuild but even at that 60-65 absolutely tops.

5) 60FROG - Engine is a delight thanks to Scott McDonald's build efforts and Bill M's wrenching abilities, but 60FROG is able to cruise effortlessly at 70 MPh when needed, I ran with traffic on the I-15coming back into San Diego turning a steady 80 Mph and even popped it up to 85 Mph without an issue or a hesitation. The car felt absolutely Rock Solid and I was comfortable even at 85. And yes I was being passed by pickups with big tires doing 90. Those you heard and felt coming before they would overtake you. Mirror visibility at that speed is not good but stay in your lane, flow with the traffic and just fine.

6) Canyon carving - Bill Mayer introduced me to some great roads to the West of San Diego. Lot's of fast turns and high speed turns and the 5 speed ration were just perfect. Those were mainly run in 3rd and 4th gear as there is a performance drop off when you shift into 5th. It is an overdrive. But running in 3rd and 4th in those twisties was a whole lot of fun.

Will I install a 5 Speed and a 3.9. You bet, I bought Gerard's Kit several years ago and I found a 3.9 from a lister many of you know from the Velocity Channel, Mike Joy, that is on it's way to me next week. If you want a 3.9 just talk to the folks on mgexp board and you will likely find one. 3 people responded to my inquiry over there looking for one. The 3.9 IIRC is simply a drop in, replace gasket, add a set of EN17 Axles which I acquired as well and replace the Radius Arms Bushings and Spring Bushings and you have transformed a BE Rear end.

To go even better I found a rebuilt 1275 +.040 = 1,326 from another forum member that will go into Bugsy IV as well. It will be here next week. I will drive Bugsy IV for the next few weeks until it gets too cold and then start with the rebuild project and mods I am planning on making to Bugsy IV. Hoping by late Spring I will be able to drop in the engine and tranny. I will drive ugly all Summer and Fall and pull him apart for Paint over the winter, and hopefully reassemble and thrashing in Late Spring next year. Going to be fun,

Do you want to add the 3.90 Pumpkin. An absolute YES. The combination of the 5 -Speed and lower Rear End ratio will transform your LBC.
 
Jim_Gruber said:
OK I think I can weigh in on this as I can compare my old '68 Sprite Bugsy I with a 4.22 Pumpkin to driving Bill Mayer's 60FROG with a 3.9 rear and a 5-Speed.
1) First and foremost, Synchro First Gear. Year, a usable First Gear that transforms the car.

2) First Gear with a Datsun 5 Speed is a lower gear ratio that a Ribcase 4 Speed. You will find that you will run out of first gear faster and need to shift sooner without the 3.9 Pumpkin

3) I noticed very little perceived performance difference in 1st Gear in fact I think it was enhanced with better matched tranny and read end ratios.

4) The real beauty is simply being able to stay with Modern Traffic. Bugsy I in spite of rebuilt shocks, rebuilt front end, all new bushings was really pushing to get over 60, 65 a bit scarier, and 70 engine absolutely screaming and it felt uncomfortable to go there even on a smooth expressway you were fighting to maintain any sort of speed. Now that engine was quite worn and definitely needed a rebuild but even at that 60-65 absolutely tops.

5) 60FROG - Engine is a delight thanks to Scott McDonald's build efforts and Bill M's wrenching abilities, but 60FROG is able to cruise effortlessly at 70 MPh when needed, I ran with traffic on the I-15coming back into San Diego turning a steady 80 Mph and even popped it up to 85 Mph without an issue or a hesitation. The car felt absolutely Rock Solid and I was comfortable even at 85. And yes I was being passed by pickups with big tires doing 90. Those you heard and felt coming before they would overtake you. Mirror visibility at that speed is not good but stay in your lane, flow with the traffic and just fine.

6) Canyon carving - Bill Mayer introduced me to some great roads to the West of San Diego. Lot's of fast turns and high speed turns and the 5 speed ration were just perfect. Those were mainly run in 3rd and 4th gear as there is a performance drop off when you shift into 5th. It is an overdrive. But running in 3rd and 4th in those twisties was a whole lot of fun.

Will I install a 5 Speed and a 3.9. You bet, I bought Gerard's Kit several years ago and I found a 3.9 from a lister many of you know from the Velocity Channel, Mike Joy, that is on it's way to me next week. If you want a 3.9 just talk to the folks on mgexp board and you will likely find one. 3 people responded to my inquiry over there looking for one. The 3.9 IIRC is simply a drop in, replace gasket, add a set of EN17 Axles which I acquired as well and replace the Radius Arms Bushings and Spring Bushings and you have transformed a BE Rear end.

To go even better I found a rebuilt 1275 +.040 = 1,326 from another forum member that will go into Bugsy IV as well. It will be here next week. I will drive Bugsy IV for the next few weeks until it gets too cold and then start with the rebuild project and mods I am planning on making to Bugsy IV. Hoping by late Spring I will be able to drop in the engine and tranny. I will drive ugly all Summer and Fall and pull him apart for Paint over the winter, and hopefully reassemble and thrashing in Late Spring next year. Going to be fun,

Do you want to add the 3.90 Pumpkin. An absolute YES. The combination of the 5 -Speed and lower Rear End ratio will transform your LBC.
Click to expand...

Mikes working as we type this...Barrett Jackson on Velocity.
Rut
 
I have a 3.9 going into Innocenti C over the winter.

Cheers

Mark
 
Dang! something else I've got to buy! Doug (for the 1275 car; don't think the 948 would have fun pulling it - even with the 5 speed).
 
Fantastic summary, Jim. Excellent advice here. So, I'm going to take stock in all the bits I have (or can easily get from my friend) and try to get going.
 
Mark go for it. Changing the diff out appears pretty simple as long as you don't mess with pinion big but on there. It needs to be torqued to 140 lbs. There
is a pretty simple way to do that if needed using your workbench top with a couple of pieces of angle iron to hold things stable, but it should unbolt
pretty simply and swap in another. While you are doing that swap out rear wheel bearings with Volvo sealed Bearings someone will supply the number and help solve alleged shaft leaks onto your rear shoes and swap out axle shafts from a later Spridget to EN17 half shafts. Those won't break near as easily as BE half shafts. End result better ride, performance, and reliability.
 
Subaru Sealed Wheel Bearing help to solve rear half shaft leaks, not Volvo. Someone please post the number. It's on the Wiki Page here an article on swapping out.
 
BTDT with most of what you have covered but very nice that you are covering it for those who haven't, Jim. Wanted to add that if you need to change a rear diff pinion seal its easy to make up a pinion flange holder by drilling a couple of holes for the flange bolts in a heavy piece of strap. Then when retorqueing just don't go quite up to the original specs or mark the nut and shaft before unbolting and only return to that mark.

Kurt
 
Kurt do I need to remove the BF Nut to change the Diff Out. I think you are saying yes. Can you post the picture of the rig you set up on your workjbench to lock it down. It will save me from hunting it up. Thanks.
 
No, no BF nut, just if you need to change the pinion seal. To change the diff's you just need to pull the axles and unbolt the unit from the rear axle. Well, brake line and drive shaft of course. Just wanted to add that. Need to acknowledge that this is Marks thread....don't mean to be changing the subject.

Kurt.
 
Jim_Gruber said:
Kurt do I need to remove the BF Nut to change the Diff Out.
Click to expand...

If you are just swapping the entire diff as a unit, you don't need to mess with the big nut on the pinion of the diff. Just disconnect the drive shaft and unbolt the diff from the housing (after pulling the axle shafts). New gasket, bolt the new one in place.

Now, that said, with the diff out it's a good time to replace that pinion seal if needed.

Subaru sealed bearings for the wheel hubs, Timken 207FF. I've got a set of these to go into my Morris (same-ish rear axle) when I get a moment.

https://www.amazon.com/gp/product/B00153XT8Q/ref=oh_aui_detailpage_o07_s01?ie=UTF8&psc=1
 
I have a set of double bearing hubs to install at the same time
Since I have 7 inches of tire width on the road this maybe the way to go

Cheers

Mark
 
Drew,

Tha's what I thought. Now that Pinion Seal may be suspect as there is oil on the front of the differential. Need to look at that closer when the time comes. Now to resolve the electrons are not making power issue. Generator is TU and so is the one on my spare engine. Too many years just siting. The one on my 1275 is rusted up pretty solid.
 
Drew,

Tha's what I thought. Now that Pinion Seal may be suspect as there is oil on the front of the differential. Need to look at that closer when the time comes. Now to resolve the electrons are not making power issue. Generator is TU and so is the one on my spare engine. Too many years just siting. The one on my 1275 is rusted up pretty solid.
 
Back to top of forming look for link to Technical Articles. Also use search feature.
 
Back
Top