"33" Banjo rear end issue

J

Joliet Jake

Member
I have a 33 banjo rear end with 4.11 gears, not long ago I purchased a banjo center section with 3.78 gears. I planned to use the new center section but here lies the rub. The original center section measures about 3 1/2 inches wide and the new one is 4 inches wide. Does anyone have a clue as to what the 4" unit might have come from or if it will bolt up and work or do I just remove the ring and pinion and install them in the old case.
 
I put the 3.78 into my 33,used the 33 compete housing etc,only use the 3.78 pinion and ring gear and do a bit of maching on the 3.78 parts.
Some one will chime in with the complete proceedure,if not let me know and I will dig it out.
It is a very good conversion.
Lawrie
 
The late '32 thru 34 rear end had a narrower center section then the '35-'48. The late pinion will not fit the earlier center section unless some major machening is done. You need a set of early gears for your 33 rear end.

If you can not find a early Ring and Pinion, MAC's lists a 3.54 Ring and Pinion for your rear end EXCEPT the pinion has 6 splines insted of 10. You will have to modify your drive shaft to accept a 6 spline pinion which is not too difficult.

I hope this helps,

Chris
 
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Holy friggin crap, I have a set of gears that I can't use. I wonder if I can find someone that will buy them, boy this sucks. :( There are some great machinists where I work, where might I find instructions and pictures?
 
I will see if I can find ther old Barn post and post it today or tommorrow.don,t throw away the 3.78, after you install it you will be happy.
Lawrie
 
I cant find the sheet,but here is what you have to do.
machine down the 3.78 pinion shaft diameter where the bearings mount to the same as the 4.11(33-34) diameters.
Make a 1/2 inch spacer(check this to make the distance to the nuts the same as the 33-34) to go between the pinion bearing nut and the outer pinion bearing.(so the dimension is the same as the 33-34)
Machine the outside diameter of the 3.78 pinion gears just enough to fit into the 33-34 pinion bearing center housing,( this can be done on the lathe and is only a small amount)
You may have to grind or machine a small champer on the back of the ring gear to clear inside the 33=34 housing.(I did not have to do this on mine)
Fit all the spider gears from the 33-34 into the 3.78 carrier.
Bore the 33-34 driveshaft female 10 tooth spline out to suit the OD of a 6 spline coupler,
Measure the lenght to the retaining pin hole and get it the same as the 33-34,(check this very carefully) I did mine by measuring the distance from the centre section face where the torque tube bolts up to out to the end of the driveshaft (gearbox end),on the 33-34 and make it the same.and tig weld it in.check the shaft for straightness after.
I did all the maching on my lathe using insert tools,it is basic machining and easy.I also did the welding but got the shaft checked and balanced at the local engine reconditioner.
I can say one thing that it was sure a good mod, and as you use ford made gears they are nice and quiet.
Lawrie
 
It is a LOT of work to get your 3.78 gears to work and the difference between the 4.11s and the 3.78 is only about 8%. That means, for the same road speed, with 3.78 gears, your engine will only be running 8% slower then with 4.11 gears.

If you ran 3.54 gears, your engine wiould be running about 14% slower.

For example, when running at a speed that would turn your engine 3000 RPM with 4.11 gears, you would be turning about 2760 with 3.78 gears or 2580 with 3.54 gears.

I would consider 3.54 gears.

Again, just my opinion.

Chris
 
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Thanks for the advice Lawrie, I'll take this info and get with my machinist friend at work and see if he can help me pull this off. CW, you are quite right about the difference between the two gear ratios and the benefits of the 3.54, my problem is having a tight budget to build this thing, I don't have the extra cash to buy new gears, if I sold the 3.78s I could put it toward the higher gears so as you can see I'm stuck with them. The machinists I work with love a challenge and enjoy "Government Work" anyway so I'll roll the dice and see what I get.
Thanks again:D
 
The one BIG advantage of using the 3.78 is most times they cost nothing,3.54 cost a lot. especially the early 10 spline ones.
Lawrie
 
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