Some of you may know the rich Genesis history with Classic American Muscle Cars.  The stable includes Jason's 1969 Firebird, Braden's 1966 LeMans Convertible, and my 1969 GTO Convertible, 1970 Plymouth 'Cuda, and 1972 LeMans Sport Convertible.

Last year in the '69 GTO and the '72 LeMans, I decided I just wasn't happy with the "get-up and go" factor.  Sure, these have Limited Slip, and around 400 naturally aspirated horses each, but the 3.23's just weren't giving me that performance satisfaction I desired.  Cutting to the chase, I put Richmond 4.11 gears and Auburn Limited Split Differential units in both cars.  Yesss!  Off the line performance was EXTREMELY satisfying now.

Short side story (Ok, maybe is a long-short story): When your better half is out of town for the week, and JEG's will ship just about anything overnight (including Saturday), and you have too much free time on your hands, and your brothers didn't even try to talk you out of it (and perhaps even egged it on...), well..., anything is possible.  Got the rear-end parts on Friday morning. Laid low until the wife was safely out of town, and on Saturday evening, started the upgrade.  Being the control-freak that I am, naturally I would only trust myself and Brad (brother) to do the work.  Cut to 12:00am, Sunday morning,  gears in place.  I let Brad and Braden take the GTO out for the first test drive (or should I say "beat").  I could hear them burnning off the tires all the way back to the shop (picture in your mind "shaking up the bee's nest").  Now, any sane person would have just put the car back in the garage and called it a night.  Sanity is not one of my strong points when it comes to these cars.  I decided I'd make a quick run up to the local Burger King and get a snack.  They say "Possession is nine-tenths of the law" - and when Ralston's Finest (the angry bee's) pulled me over I was read the riot act.  Let's just say, I had to use my "once in a lifetime" "all day traffic school so you can still afford insurance" option.

Ok, back to main story....

The gearing and performance are unbelievable, however, with 4.11 gears and a 3-speed THM-400 Automatic, we'll, your RPM's are way up there.  The engine doesn't care, and performance is still there (both Pontaic's have 400ci engines, balanced, MSD Ignition, good for 8 to 10,000 RPM - not that you'd do that....).

Enter Gear Vendors.  These guys have an under/overdrive "gear splitter".  Basically, it takes the 4.11, and when you kick in the gear split, it equates to having a 3.23 rear end ratio.  Technically, it splits all 3 gears, do effectively you turn your 3 speed in to a 6 speed - 1st, 1st-Split, 2nd, 2nd-Split, 3rd, and 3rd-Split.  These things are ROCK-SOLID.  Let's put it this way - you can smoke the tires with the 4.11's, through 1st and second, start into 3rd, and as you are moving, split the gear - and get tire chirp as it shifts!  Try that with a regular old "overdrive".... By the way, these guys know their stuff.  I purchased my GV Unit direct from them, and they asked the right questions, and the delivered product was EXACTLY what I needed, including every nut, bolt, gasket, etc.  Even my speedometer, which previously did not have the correct speed shown, now matches perfectly!

The GV unit is unbelievably simple to install.  Takes just a couple of hours.  I was spoiled, I used a car lift, but you could just as easily just put the car up on ramps and use a creeper.  Highlights from the install:

A lift makes all the difference....
 

 Carefully review your parts list....  Let's see... Where are the band-aids..?

Hmmm... Since the GV adds like 18" to the transmission, you gotta shorten it, or, better yet, just have Inland Truck Parts build you a new one!

Here's the "before" picture looking at the tail section and trans mount, standing at the rear of the vehicle.

If you're squeamish, close your eyes (most people go their entire lives without seeing this internal view of a transmission. Pity.)

Since we are adding length to the trans, a little massaging of the trans tunnel is required.  Not too bad.

 The trans crossmember has to be flipped over and around, and then just trimmed a wee bit to make it fit.  It's times like these that help to explain to the wife exactly why you needed that plasma cutter! 1) Marking, 2) Get the plasma ready, 3) Nice clean cut, 4) Little touch up.  Not shown: Bead blast, paint, air dry.  Mmmm.... Tasty....

Here's the fit with the new driveshaft to splitter to adapter.

Once the "mechanicals" are in place, it's just a matter of the Speedo adapter, and wires that feed up under the dash to a hidden computer control module.  A auto/manual switch is mounted under the dash to determine if you want the device to shift automatically (Auto-Drive) or manually when you tell it to (I mounted my manual shift button above and to the right of the high beam switch on the floor - just the perfect spot to move your foot up and shift for power!).  No pictures of this part of the install as, really, it's not even seen in the car - the casual observer would never know you have the GV unit installed - until they hear it shift!

The only physical mods to the car are: Modify the transmission mounting bracket (slight trimming), round out the transmission hump (to make room for the GV unit's bolt "ears"), and cutting (or replacing) the drive shaft.  That's it.

So, how do I like it?  This is a pricey solution, but for the shift performance, and ease of use (you can set it to either manually go into overdrive, or you can "auto-drive" so it shifts just like an automatic 4 speed), absolutely no performance loss, better gas mileage, the list goes on....  What else could you ask for?  I HIGHLY recommend it. In my scenario, you get the best of both worlds - 4.11's when you need 'em, and 3.23's to satisfy the gas miser.  The performance is phenomenol!

BJ Williams
President / Chief Software Architect