Hello guys.
Thank you for all the help so far
I have a 64 to 66 A833 that i would like to convert to an overdrive style. Ive read that Passons makes a kit. And brewers also make ones. Which would would be the best that would not require me to modify the tailshaft ?
This is a hard read for me;
1) Do you want to convert your trans, as in take it apart and install the overdrive gears? or
2) Do you want to drop your current trans, heave it into the back-40, and then buy/install a good used overdrive box?
I mean reading your post, I think both scenarios are a valid read.
As to the first case;
!) this assumes that you already have a 4-speed, as in your opening sentence.
1) there is almost no point in trying to install the overdrive gearset into your 4-speed box. There is a strong chance that the od cluster will not drop into your box without some grinding; and the mainshafts are not interchangeable, the od shaft has to stay with the od gears.
2) the alloy F-body box is almost always aluminum so, weighs almost nothing, and so yur not saving much in the shipping of guts only.
3) but if you have a B&T, Ok I get what yur saying. and I know of no factory parts to swap in and still keep the B&T. However, any good machine shop, can marry the two shafts, cutting and welding the od mainshaft to the B&T output. But just cuz they're married doesn't mean they'll stay married with say 360 power.
I once worked in a machine shop, that specialized in work like that and it was never cheap.
as to the Second case:
1) The overdrive box is a direct bolt-in swap, with it's associated Bellhousing that has the jumbo 5.125 retainer opening..
2) yes you can work around that, but it may cost you the same money as just getting the matching BH, with it's matching fork, and stand-off bracket.
3) I do not know if the 64>66 cast-iron tail
with a slip-yoke, is any different from the 67 ups. But I do know that the rear mount is in the same place as the 67. and of course the B&T is a can of worms.
4) whatever yoke your driveshaft has, be it a 904 size or a 727 size, if you plan to keep it, you will need the matching small-splined Mainshaft in the od box.
5) after that, you should be golden.
Having said all that;
1) the overdrive in that trans is a .73 ratio. which means that your rear gear will be reduced to that .73 amount. So if you have 3.23s for instance, those will now be 3.23 x .73= 2.36, and 65=2100 with 24.5" tires.
2) This is about as slow as you want to rev, cuz even 2100 is hard to get optimum timing advance to get optimum fuel economy. In fact, I think 2400 would get better fuel mileage after the Cruise-Timing is maxed.
3) As to the rear yoke, the 904 sized mainshaft is almost puny for anything bigger than a stock low-compression, 150hp, smog-318. If you have more engine than that, I recommend the 727-sized mainshaft and get your driveshaft modified to fit. I'm not saying a 360 will tear it up, jus offering my opinion.
4) your 4-speed floor-shifter should work, if the adjuster can accommodate the flipping of the 3-4 lever.
5) there are two sizes of overdrive gears, the low-power variant with just 18 teeth on it, and, what appears to be a slightly stronger version, the 20Teeth.
IMO, the 18 tooth one is barely adequate for a slanty.
6) This trans, people will tell you is a 4-speed, cuz all the gears are in the mainbox. But if you shift it like you do your standard 4-speed, you will shatter that od gear into a handful of garbage, and nobody knows if those parts will take out the rest of the box as they explode. Therefore treat it as a Three plus one. Always be gentle on the last up-shift, and you'll be ok. If your hoping to bang gears, this is not the box for you.
7) if you already have the Commando box with the 3.09 low gear, then you already have, IMO, the nicest Mopar 4-speed, with 16% more starter gear torque multiplication than the standard box. This allows 16% less rear gear for the same low-gear performance as the standard box. So if your looking for fuel economy, a smaller rear-gear may be an option. and you will like that way more than the wide ratios of the overdrive box, and the delicate overdrive gear.
8) If you do this, and when you blow it up;
Put it into neutral as fast as you can and shut the engine off, then take your foot off the clutch. This will cause all the gears to come to a halt, and the only parts left spinning in there are the synchronizers and the mainshaft. If yur lucky, maybe the other gears escape catastrophe.
9) When I was running that box, I always had a spare. I broke three of them before I abandoned them. I have, since then, found and procured the missing parts for one of them, which is now, awaiting assembly, in the que, together with the spare.
Happy HotRodding.
