Auto to manual conversion. If you could do it over....regrets, pitfalls, long term opinions???
My regrets? I always thought that the wide power band and torque of the 408 would respond well to an OD 833, but sold the car out of necessity before I got to try. It would have made highway cruising that much nicer.My 2 cents......
I have run every Mopar box behind my 367;the 3.09/od included. IMO to run the od box you need a low-rpm engine with a low-rpm cam.The ratios are 3.09-1.67-1.00-.71od., and the splits are .54-.60-.71
My 367 only put up with that box when it had a 270/276/110 cam and 10.9 /1 Scr. That engine revved quite high, and that saved it, cuz the 1-2 split pulled the Rs down to 54% on the 1-2shift.
Unfortunately for a streeter second gear being 1.67 was kindof an in-between gear. I like to gear my car to be revved out at 65 in second gear, so the average power during the run can be as high as possible. Well that 270* cam made peak power around 5200.And the 110LSA made the top of the curve long,broad, and nearly flat. So I used to shift her at 6000. Well,with a 1.67 second gear, this requires a rear gear of 4.44s and I used 4.30s. Well a 4.30x3.09 =13.29 starter gear. And that is a great dragrace starter-gear, but I found it to be a ridiculous street starter.
Also cruising 32 mph(with 4.30s) was 5282 in first,2855 in second,1709 in third. So while cruising there was OK, accelerating from there was painful. I either down-shifted to be right on peak-power and then outta revs; or tried to pull from 2855. If I did downshift, of course it blazed to the 6000 shift-rpm in a heartbeat. But going into second the Rs dropped to 3240, and I was back to Slow-performance. So With that box, I used to carry the Rs up to 7000, to in-shift second at 3780 where that little cam had some pull. All-in-all, not very satisfactory.
So I got me a GVOD and started splitting gears. And that made a dynomite combo. The best I ever had, in terms of ratios.
The ratios were; 3.09-2.41-1.67-1.30-1.00-.78-.55, and the splits
.78-.69-.78-.77-.78-.71, pretty tight.
On the street;this worked reasonably well with 3.23s. I was now turning 6300@65, in 2.41 ratio.With 5 more ratios to go. 65 was 1434 in double od. But the splits in the
main box were worse than ever with 3.23s. The 9.98 starter was just right, but second was just too far away for anything but casual driving. So I was more or less forced to split all the gears, and this became a PITA. I drove it like that for awhile. Then I had a bright idea; why not gear it so that First-over was actually the First chosen gear. I found that the GVOD would actually hold 1od right through a stop-light, and I liked a starter of about 10 to 11. So I tried me some 4.86s. The first chosen ratio was now 4.86x2.41=11.71. and that was pretty deep. I didn't like it much as a streeter. At the track it was great. Those 4.86s got me 108@6500, and the 15.02 starter really blasted me off the line. And the tight splits got me a pretty good ET for the poor suspension I had.
But on the street it sucked.
So I got me some 4.30s just to be sure, I wasn't missing something.And that didn't work out either. No matter how I sliced it, I couldn't have it all. All being;a nice starter of 10 to 11, and a nice downshift at 32 mph, and reved right out at 65, and a nice gear to trap with. Plus I kept forgetting to not over-work the od gear, cuz they won't take much. I zipped the teeth right off them twice.
So I did the math to find what ratios I would need to "get it all". And that tranny was instantly yanked; it was hopeless.
That tranny likes a torquey engine with a very low operating rpm.
It worked great behind my 1973 stock 318, with a 4bbl and headers. The factory cam is done by 4500, so out-shifting first at 5000, the Rs drop to 2700, right about where the teener makes peak torque. So 3.73s were the gear of choice. This got me 65=5030rpm, revved right out in second. And it got me an 11.53 starter gear. And it got me a cruiser gear of 2.65 where 65=2139. And it got me a trap rpm of 4800@ 79mph in second-od .I finally "got it all"
So the key to using that tranny is being revved out at 5000, which is about a stock-sized cam of 240*. lol And if it ain't fast enough, get a bigger engine.
You, with a 408cuber, mightta been able to make it work. But it woulda worked best with a tiny cam, making a very low shift rpm and it wouldda needed to make a lot of low-rpm torque from starting at about 2700 rpm.
IMO, tho, you mightof been better off with a regular box and gearing it for whatever hiway rpm you wanted. IMO, 3.23s wouldda been great. With 3.23s I wouldda tried the 3.09/direct4th box. These gears will get you about 65=2600. And the starter is 9.98. Shazzam! And 65=5000 at the top of 1.91second. So a real small cam is all you need with that combo, in a big engine.
But of course there is no gear to trap with properly.Third gear (1.39) would get you 5500=99mph, 6000=108, 6400=117 there it is! So the little cam is gonna have to pull a lil outside it's comfort zone. In direct,117=4700. You kindof need a half-gear there. Hmmmmm, GVOD to the rescue; 117=5100 in 3rd/over. But then, if you had a GVOD, you wouldn't need the 3.23s,lol; it just never ends.
What I finally did was to say to heck with Quarter Miling; what about in the 1/8th? And that is where I found my niche.
For you and the aforementioned 3.23s, and a little cam, you could hit maybe 93 (or a bit better), in the 1/8 and that wouldda been 5300 in third, with lotsa room for more mphs. So again, just a small cam is all you wouldda needed.
Lest anyone reading this far down the page might think 93 in the 1/8th is mundane, I know at least one guy who was ecstatic......me
The Wallace Calculator thinks 93 in the 1/8, translates to over 115 in the qtr. And it thinks 115@3650 is 445 flywheel hp.
I was a happy guy!
