[Half-Inch Stud]

Driveshaft arrived during the Thanksgiving travel to PA. Driveshaft went in fine, just nothing unusual to post photos. Has nice weld beads.

Driveshafts compared
Dennys: Forged Spicer ends & Yoke. 3.5" Chrome-moly tube
Houston: Cast Neapco Ends & Yoke. 3.5" Mild steel Drawn-on-mandrel DOM seamless tube.

Gotta add fluid, & hook up cooling fans to 12 Volt & GND.

[Half-Inch Stud]

2 Gallons + 2 Quarts later the car had a firm Reverse and Fwd. So just got back from a tst-beat.

Inetresting drive in a positive way:
Converter mode, Foot-Clutch switch byppassed.

Column works Park, R, N, OD D, 2nd i dunno about 1st. Maybe it had 1st. Floor Shifter left in 2nd. Nice 2-3, not sure about 3-4 but Tach says OD is working.

Floor-Stick Shift: 1st, 2nd, OD, i dunno about 3rd. 1-2 is great!, 2-3 (or OD) is good.

No engine braking on holding 1st. I dunno.

1 Leak: couple porous welds spots on the Tail up with Speedo ( .. gonna JB Weld )

Next run will be highway.

[Half-Inch Stud]

Tail Cup leak was found to be a pinhole ( light passing throu it ), maybe another weep or 2.

7 photos to show process leading to Mineral spirits de-grease then Marine-Tex sealing. Also used this time to prepare a 3/8 stud for the lower position because the Stick Shifter Bracket also uses that bolt/stud.

[Half-Inch Stud]

Clean and epoxied: Let cure 24 hours and will install.

[antique69lemans]

How did you jig up the pisition to weld in cup ? I have cut up one but haven't had it welded yet.

[Half-Inch Stud]

I helped establish the drill-center, and supplied
the aluminum tube having The ID close to the TH400 Speedo carrier.

So to answer the question, the alum tube & Speedo have a diameter and center, whereas the Tailcup has an outputshaft center. So the Tail diameter with speedo drive gear @ Driven gear speedo give you a diatance down from the tail center: draw a horizontal line along the Tail cup.

Then the for/aft is forgiving in whether its perfectly centered. Draw a vertical line, knowing it can be less precise.

A fella cut and welded my 2 tailcups about 5-6 years ago. Mount tailcup in a vise staged, in drill press, and holecup-drill the side wall and continue to the side for the center bit to kiss the wall. The other wall was drilled and plugged with aluminum dowel, but listen, i wanted a tapped hole there so a bolt could be staged for tuning-in the speedo stop. Bolt threads could be epoxied for leak free result and be simpler, nicer and functional.

[antique69lemans]

Thanks. I used a big muncie drive gear opend up to press on output shaft. They use the smaller gears which fit better into extension housing. I machine a hole a little oversize in housing and utilized a fixture to locate for welding.

[antique69lemans]

Originally Posted by Half-Inch Stud

I helped establish the drill-center, and supplied
the aluminum tube having The ID close to the TH400 Speedo carrier.

So to answer the question, the alum tube & Speedo have a diameter and center, whereas the Tailcup has an outputshaft center. So the Tail diameter with speedo drive gear @ Driven gear speedo give you a diatance down from the tail center: draw a horizontal line along the Tail cup.

Then the for/aft is forgiving in whether its perfectly centered. Draw a vertical line, knowing it can be less precise.

A fella cut and welded my 2 tailcups about 5-6 years ago. Mount tailcup in a vise staged, in drill press, and holecup-drill the side wall and continue to the side for the center bit to kiss the wall. The other wall was drilled and plugged with aluminum dowel, but listen, i wanted a tapped hole there so a bolt could be staged for tuning-in the speedo stop. Bolt threads could be epoxied for leak free result and be simpler, nicer and functional.

I may steal your idea of adjustable stop though... Also I drilled a tiny hole in lube galley that feeds rear bushing so it sprays on gears

[redhawk44]

Hey Stud, Great job documenting this project for everybody. All good info here.

Jeff

[Half-Inch Stud]

With any luck this AM, im going to button-up the tail-cup, driveshaft, and swap rear springs (PY HD ride) for better/proper ride then the upullit SUV springs, and drive it for Eval.

[Half-Inch Stud]

Originally Posted by antique69lemans

I may steal your idea of adjustable stop though... Also I drilled a tiny hole in lube galley that feeds rear bushing so it sprays on gears

that is a good idea, that is too late for me to implement. Oh well when the sppedo gesr cooks up i can drill a feed hole that competes with the rear bushing's rear cup-plug feed hole.


@redhawk44. thansk. Id like to see the 4L80 developed further into a serious Street/Strip "Poor Man's Lenco" keeping the locking converter for highway.

[antique69lemans]

Originally Posted by Half-Inch Stud

that is a good idea, that is too late for me to implement. Oh well when the sppedo gesr cooks up i can drill a feed hole that competes with the rear bushing's rear cup-plug feed hole.


@redhawk44. thansk. Id like to see the 4L80 developed further into a serious Street/Strip "Poor Man's Lenco" keeping the locking converter for highway.

I wouldn't sweat the lube hole in your case. The larger gear that you used is probably dipping fluid and carrying it into mesh.

[Half-Inch Stud]

Tail cup on and test drive done. Reverse is nice & no slip, without hard bang-in (like some TH400 builds can be).

1-2 & 2-3 & 3-4 shifts are real good. Tach on Highway is a trip at 2000 rpm (or less). Vacuum gauge was in the green. Car is much quieter.

was able to power thru the 1-2 upshift and keep it mostly straight, so itsa workin.

Clutch Pedal switch& bypass switch indeed work for locking Converter. Brushless Cooling fans real quiet & working the trans cooler just fine.

overflow hose has been & still is dry.

Seems to be a small drip from the Tail cup...

Overall a greatly improved car and ride with the Overdrive 4th gear. Probably take it to work tomorrow to hopefully declare "Done".

[Half-Inch Stud]

DRIVING IMPRESSIONS; Drove the Wet-Stick GTO to work, lunch and home.

AM drive; couldn't keep my foot out of it, OD, lock converter, climb in MPH, modern Red Camaro wanted to have fun. too much traffic to get past 90. Anyway the tach stayed under 3000 rpm. Cassette music was low so i could hear everything.

lunch, cassette music put loud, passenger held on to the dash around turns :no idea: really i dunno why. Nice shift bumps and OD demonstration.

Drive home: drives like an automatic because i don't have to shift down, nor have to use the clutch. So i went from red light to Highway in OD (on Converter) and was just fine. Climbed MPH and loN behold the same red camaro was jam-carred and i blew by him in OD with nothing but empty left-lane in front. Camaro pulls out but never caught up. Tach never got above 2500 rpm.

Car is quieter and more drive-able. Seems the engine TQ is more accessible. Seems the engine "performance", car performance is enhanced. Never knew the low-end RPMs had so much useable pull. Over-cammed 9.0:1 is pulling syrong and ping-free. A crazy feel; the Vac gauge still in the green while cruising and the pedal has that "tall-pedal" feel again.

So I clicked the OD off (4-3 shift) and geez the engine rpm had to go to ~3300 rpm,locking Conveter is only worth 100 RPM. 3rd gear driving is a downshift back into aweful mode on the 70 mph highway.
SHOULD HAVE DONE THIS SWAP 5 Years AGO !!

Oh uhm the speedo stopped working, so maybe th new PY speedo cable broke or the speedo drive/driven gearset failed. Gotta open the speedo up.

[Half-Inch Stud]

Moderator; propose moving this Thread to the Street section?

[Half-Inch Stud]

Today's highyway commute with GPS for MPH

2500 RPM @ 75 MPH Converter locked
2600 RPM @ 75 MPH Converter slip-mode
3500 RPM in 3rd (TH400 1:1 Drive)

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

[Heatwave]

Excellent write-up. Did you make any changes to the rear diff? What ratio?

How did you decide to go with 4L80 OD instead of for example the 200R4?

I went with the 200R4 and have been thoroughly satisifed with it. IMO, it feels and drives the way it should have all along (mine is a 1969 GTO Convertible with a 3.55posi.)

Outstanding project.

[Half-Inch Stud]

Dana60 (S-60) Rear stuck at 3.54:1

4L80 is a TH400 that GM added an R&D upgrade. Soooo, since i got the 455+060 and drive like it was stolen,i'd go up, not down in ruggedness.

200R4 can hold up. My 2nd pick was the Ford 4R70W because its OD is strong & assy is rather slick & light but needed a Bell housing swap not an adapter plate.

[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.

[1968GTO421]

Originally Posted by redhawk44

Hey Stud, Great job documenting this project for everybody. All good info here.

Jeff

X2. Thanks for the write-up and pics. Saving for future use.