Guys considering a TKO, I took a picture to show what 5th gear looks like

[chilly460]

I've had a little time to put miles on my TKO 500 combo now as well, Ross.  Background info, 390/TKO 500 with .68OD/4.10gear/'63 Marauder.  I have same rear tires as Ross, 275/60/15s, so RPM/MPH info is the same. 

I run a 750dp/Performer RPM/Comp 270H which is 224* on a 110LSA advanced 4*.   So, 100cubes less, fatter car with more frontal profile, cam is smaller but I'd bet a 224* in a 390 is same ballpark RPM and vacuum wise as a 242* cam in a 489?  I always went by the rule of thumb of adding 6-8* of duration for every 50ci of displacement to keep RPM range the same.  I'd also guess your solid may act a bit "smaller" even with the tight lash, but splitting hairs. 

I just drove it down to Va International Raceway last week, 400mi round trip.  Ran mostly 60-65mph, car pulls great at the 2000rpm cruise.  We were on a secondary two lane with some quick "rollers" through the foothills that were fairly steep and they just required a little roll into the throttle, no problem.   Slower sections through town 45mph/1500rpm, just for fun I stayed in OD, it will handle it but throttle response is basically nil and it does one "chug and go" when rolling back on it, but it doesn't buck.  I'm sure if I wanted to play with the power valve I could get it to pull clean at 45mph but I'm not going to be in the habit of lugging it.   55mph is 1750ish rpm, no issues and pulls clean, will gain RPM on uphills with a little throttle so doesn't feel like it needs a downshift. 

I'd say this gear/trans combo is "perfect" for my needs.  Virginia has a bunch of really nice two lanes so the 60-65mph zone works well.  I have spun it up to 70-75mph for long stretches (75 is 2500rpm) and that works well too, so I can hang with interstate traffic just fine as well if needed.  The SLR is pretty steep with the 3.27 first, but it works well to get the heavy car moving.  Also, I had to extend the z bar arm to work in my car, losing a ton of leverage on the clutch, making it very "heavy".  With the deep first gear I can actually roll along at idle in traffic situations without bucking, nice to not have to keep working that heavy clutch pedal.

Granted, my combo is very mild.  As has been stated already, trying to figure out the sweet spot for more street/strip type stuff would be interesting, especially for smaller displacement stuff.   

[jayb]

For those that have a GV under/over unit, how well do you like it? Reading up on it, sounds like an interesting invention that has been around for a long time. For someone interested in keeping a car original but wants an overdrive, this sounds like the right product to use a toploader.

I have three of them, and they are great, especially for automatics.  For a manual, with the Tremec transmissions available I think I might lean that way, but one thing about the GVOD in a Mustang is that it doesn't require any modificaitons to the floor, whereas a little cutting and fitting is required with the Tremec (at least in my case). 

[cjshaker]

I believe you'd have a hard time finding anyone that didn't like their GV overdrive. When you have 3000 horsepower cars using them without issue, that says a lot.

[66FAIRLANE]

Still loving my GV unit with C6, 3.89's, 3000 converter and 26 inch tyres. As Drew said though the gear splitting thing is not really an option. You would have to have large plums to pull it out of OD on redline at the same time it hit the next gear. Feels like a recipe for scattering parts. Might actually be easier with a manual though.

[BattlestarGalactic]

Nothing like an old 428CJ screaming along at 3500rpm at 65 mph with a toploader and 4.56 gears!!!  Why would you want anything else?? It's just in the sweet spot of the cam and when you want to pass someone you just tip in the throttle a bit and it runs up to 5000 rpm in a wink of an eye.  LOL!!!!  It drives like an old '69 pickup should.

What??...........
 

[jayb]

Larry, you are hard-core LOL!

[BattlestarGalactic]

Ya, that and I don't have $2K for a fancy overdrive kind of transmission. 

The black car isn't quite as bad with 3.89 gears and 275/60/15 tires.  It is about 3000 RPM at 65 mph.  It just kinda settles in and doesn't really care.

I remember, way back when I bought my new '99 V10 CC DRW truck to pull my trailer and with 4.30 gears I had thoughts of putting a GV on it.  But, again, the cost was prohibitive.  Funny how money makes a lot of my decisions??   

[AlanCasida]

I have Gear Vendor units in three of my older vehicles and am happy with them as well. I got all mine used off of Ebay and paid considerably less than half price for each.