overdrive

[62galxe]

Looking for opinions from this knowledgeable group. Wanting overdrive behind my 390. rear gear is 3:73. Most expensive is the 4R70W due to bellhousing mods. Broader Performance can build it with Baumann controller. The other option is gearvendor. Which way would you go and why.
Thanks

[59meteor]

What will you mainly be using the car for? If your 390 is fairly mild, and you are not driving it too hard, a T5 speed is a pretty sweet transmission, but its not strong enough to be racing with a healthy big block with slicks, especially in heavier cars. But they will take some abuse. I ran a junkyard T5 in a couple of my old street strip Fairmonts with warmed over 302s and 3.55 gears. 60 mph in 5th gear was about 2100 RPM, with 24" tall tires. With the previous C4 , it was almost 3000 at 60. The Fairmont weighed 3300 pounds with me in it, and ran low 13s and occasionally high 12 second 1/4 mile tires and I never broke it, although I did break a couple in my 85 Mustang, which was a bit quicker, and driven harder. If you want to stick with an automatic, I believe that there are adapters available to install a Ford AOD behind a FE, but I have no personal experiance with those. I know a few guys with Gear Vendors, who really like them, but they are quite pricey.

[lalessi1]

What transmission do you have now? I have a Toploader behind my 462 FE and I was thinking about an AOD. I wound up putting in a 3.25 gear replacing my 3.89. My car runs 2700 rpm @ 70 mph, not too bad. Car is much better to drive now. I do like the gearvendor OD but I don't think I would put one behind an automatic.

[Ford Blue blood]

Ford put a 3 speed with 4th overdrive in F150s in the mid 80s.  They were floor shifted, used the top loader case (aluminum) and bolted up to the 390 bell housing.  I installed one in a 48 F-1 behind a 67 Fairlane GT 390 with w 4.11 rear gear.  Nice highway cruise at 2500 RPM at 70 MPH (if I'm remembering correctly).

[62galxe]

have a c6 now. Want to stay automatic.

[Wirenut]

I have the AOD and 3.70 gears and I am pleased. I have a warmed up 302 with a small cam so not a real tire burner on the 57.
The biggest issue I had in the initial set up was adjustments to the shifting and tranny pressure settings. I had to work at getting it right and worry about burning it up on my test runs. Everything I read about pressure readings and adjusting the shift linkage were saying how easy it is to burn one up if not adjusted correctly. It took me several attempts but finally got it right. What appears to be a kick down adjustment and linkage is actually a shifting and pressure adjustment that has to be spot on with the carb linkage, plus confirmation of pressure with an actual gauge hooked to the tranny to confirm its the proper pressure at idle.
I had some second thoughts about going with that tranny but I'm glad I did plus no electronics like on the AODE. 
Good luck in your research and decision.

[81TTA]

Ford put a 3 speed with 4th overdrive in F150s in the mid 80s.  They were floor shifted, used the top loader case (aluminum) and bolted up to the 390 bell housing.  I installed one in a 48 F-1 behind a 67 Fairlane GT 390 with w 4.11 rear gear.  Nice highway cruise at 2500 RPM at 70 MPH (if I'm remembering correctly).

Sounds like the original post might be thinking of automatics only.  But, I'll throw my experience with the toploader OD transmission out there in case someone else is interested in a manual OD swap. 

Last year, I installed a toploader OD in my Dad's '57 behind a (we think) 360FE.  We think the previous owner swapped in a 360 and 3-speed toploader combo from a '68 F-100.  Anyway, we started with a 4-speed wide-ratio toploader swap that also changed from 3-on-the-tree to floor shift.  Then, for better fuel economy/lower highway RPM, we swapped the 3.56 rear end for a 3.00.  The rear swap brought the 70 MPH RPM down from ~3500 RPM to ~3000 RPM.  But, it had the obvious disadvantage of requiring a LOT of clutch slipping on launches.  Not the end of the world.  But, it wasn't hard to get the clutch (not old or worn) to chatter if trying to launch to aggressively. 

After hearing about the toploader OD, we started looking at the specs.  There are a number of differences/applications for toploader OD transmissions.  We chose a version that likely came from a Granada.  With the exceptions of the usual differences (bulge on main case to make room for bigger diameter OD gear and different shift mounting on tailshaft housing), it looks identical to the wide-ratio version.  We thought the 3.27 first gear vs. 2.78 would definitely help the launch.  Plus, the .8 OD 4th gear would bring cruising RPM down from ~3000 to ~2400.  And, that's exactly what happened.  Again, there was an obvious downside to all this.  The big gear ratio changes definitely take away from the "performance" feeling he had with the wide-ratio transmission.  While the car is more cruiser than racer, it's still a lot of fun to get on it and scoot whenever the feeling comes along!!

After all this, I now know why Tremec has a 5-speed available (TKO500) with a 3.27 first gear.  It would "solve" all the problems we've encountered.  Deep first gear for good launches with low rear ratios.  Deep OD for low cruising RPM.  "Extra" gear in the middle to improve performance.  The big problem there is $$$.  The lowest price I've seen is ~$2600.  After spending $600 for the toploader OD trans (including rebuild), it's quite the sticker shock to try to overcome. 

I'm wondering if a step to a T-5 might be worth it knowing the limitations and warnings you'll see with the first search on the transmission.  The other issue for us is shifter location.  Actually this would apply to both the TKO and T-5.  We're still running, and would like to keep, the original bench seat.  I've been able to machine "offset" shifter mounts and modify/fabricate shift rods to get the shifter positioned so it doesn't contact the seat.  My impression with TKO/T-5 is that the shifter location options are much more limited.

Sorry if this goes too far from your original question.  I hope you can find something that works for you.  If there's anything that might apply from my story, keep an eye on the transmission ratios.  It's easy to get caught up thinking only about the OD gear and cruising RPM effects.  I'm more familiar with GM automatic OD transmissions rather than Ford.  In the GM world, there's a lot of conversation/controversy between two popular automatic OD swaps due to their different 1st gear ratios.  The general argument is that the deeper 1st in one of those is "bad" because of the big change going to 2nd will cause engine RPM to drop below a good "performance" range.  I don't know if there are different offerings like this for Ford automatics or not.

[62galxe]

I was looking at gear ratios also. The 4r70w has a 2.84 first and 1.55 second. The electronics make it a little pricey but the ease of adjusting shiftpoints and lockup would be nice. The OD drops the rpm by 1000.

[lalessi1]

I found it useful to look at shift point speeds in each gear for different rear ends when I was deciding to change my rear gear. With a 28" tire and a 5500 rpm redline these are numbers for my car before and after. I have a wide ratio Toploader, 1st 2.78, 2nd 1.93, 3rd 1.36, 4th 1.

       Rear End              3.89              3.25
       Speed 1st             42.4              50.7
       Speed 2nd            61.0              73.1
       Speed 3rd             86.6             103.7
       Speed 4th            117.8            141.0

I compared my overall 1st gear ratio.. 9.035 (2.78 x 3.25) with a close ratio Muncie (2.20 1st) and it wound up being the same as the Muncie being paired with a 4.11 rear.

Before with the 3.89 I could almost dump the clutch at idle and the car wouldn't stall at all. Now with the 3.25 it takes a little throttle like a normal car should. This is the online calculator I use.

http://www.advanced-ev.com/Calculators/TireSize/?ratio=2.275

[gasman826]

My turn.  I went up and down this road with the Y-Block looking for the right overdrive transmission without satisfaction.  When the Y-Block went away, it was replaced with 351w.  This opened the door to several less expensive overdrives.  As OP, I wanted to stay with an automatic.  AOD (because of manual shift control) were seldom if ever behind a 351w.  So with an improved 351, I also needed an improved AOD.  Building an AOD with 4R70 gear set, 3000 RPM stall converter, all the upgrade, clutches, band, servo, clutch packs,
3.89 gear with TrackLoc, and LENCO valve body is not cheap.  I am very pleased with the results but it was a lot of work. 

Since you already have a C6 and like it, Gear Vendor would be an easier install and cheaper than a custom transmission install.  This would give you 6 speeds to boot.