[redhawk44]

85 thru 100 MPH is easy access and really tough to keep one's foot out of it. Louder the Cassette music the faster the car seems to go

Thats funny ***** right there. The only problem is that you likely wont hear that sirens having this much fun.

[Half-Inch Stud]

Originally Posted by Heatwave

How much HP in your 455? Did you have to modify the tunnel for 4L80?

My 200R4 is rated at 550hp. Handles burnouts with no issue but I don’t run it at the track. With the 3.55 posi rear its the perfect combination for local and highway riding. I have to agree, once you’ve had the OD it would be hard to go back to the TH400.

I also installed the Shiftworks kit with lockout and reverse backup lights. The kit makes the the shift markings look like they came from the factory and locks out the ignition unless its in Park or Neutral. Also had to upgrade the flexplate and yoke length. The speedo gear is absolutely perfect and within 2mph compared to gps at all speeds.

400-430 hp (i made more power when i was dumber, and hope to find a nut again)
stock tunnel, no tunnel mods.

drove to work today and yea fat footing it in the AM seems to be a culture on the local highway. PM is dark so the clowns are going 70-82

[antique69lemans]

Any updates ?

[Half-Inch Stud]

Originally Posted by antique69lemans

Any updates ?

Swapped in a Ported Dual-Plane for the Torker I , kept the 1050 & 2" Spacer.
Drove a bit and some modern Mustang wanted to get sporty so i did, and a few enthusiastic miles later we made turnoffs. Seems to me the Engine-Trans combo performed quite well, no loss in response or power, maybe an improvement. Even if same power, it should be a gain at low-end but idunno.

As for the 4L80; easy breezy to control it. Seems to do well just being left in OD and Converter Mode. Manual drop to 3rd feel like drop s to 2nd but the speeds were 80-90 MPH so the OD really opens up the performance window above 55 MPH. I do not miss the TH400 while on the highway. That is a clear update.

on the other hand, I do really like the TH400, and figure the best breed result is to run the TH400 with a rear gear that is 0.75* 3.55:1, for equal performance from say 20 MPH to 150 MPH. That would be a 2.66:1 rear. Round down to 2.54:1 or round-up to 2.73:1. 455- powered cars ought seriously seek a 2.73:1 rear for modern use for best full-range fun.

[Half-Inch Stud]

Update: Sold the 68 GTO with OD in May 2023.

4L80 did fine, however:
Tailcup leak (speedo gear weld-in)would come&go, but finally stopped leakin.
Speedo drive gear spun free on output shaft: never did the Stock TH400 steel keeper deal.
Shifter would bump out of OD going uphill, so added a detent (spare Ssteel Shoulder-belt Loop to catch&hold Hurst rod at base)
No rattles, no contact with floor, and the dipsticktube clearance was fine.
Reverse was optional at Cold-Start, Rev came alive and avail about 30 seconds after Cold-Start.
If i had to do it over, i'd use the Console Shifter car.
Brushless PC Fan cooler never gave a trouble, sight unseen was real nice.
Never puked, so don't recall ever adding fluid.
Stock Converter was fantastic.
Lost Foot Clutch pedal "locking converter" ability after a year, but is a gimick to stall the motor at a light. Never needed to lock it on highway.
Dramatic MPG increase.
9.0:1 455+060 felt powerful, beyond HP ratings in OD on Highway, yet flatfooted if in 3rd at speed.
Floorjack used in install finally failed this Fall (new in ~1980)! So 43 years hard use was good.

Fella that bought the 68 will likely/eventually revert to a Muncie combo, and free-up the 4L80+Adapt plate+Shifter+ Driveshaft combo.

[Half-Inch Stud]

Tech compare:
4L80 0.75 OD with a 3.54:1 makes 2.67:1 in 4th gear only. 3.54:1 in 1st, 2nd, 3rd.

TH400 with a 2.73:1 is close, but suffer the 2.73:1 in 1st, 2nd and 1:1.