[Vid]

I’m finding these answers and comments very interesting! It’s hard to imagine 4:33’s in a more or less daily driver let alone with a stock rod Pontiac.

I’m building up my stroker and want no problems from Mustangs or Civics at stoplights so I’m considering 3:73’s to 3:90’s when I swap to a 9” rear, I just don’t think I have he guts to go much taller. Strictly around town driving, no long distance highway driving. Anybody running 4:11’s with a Muncie? Do you leave the driveway in 3rd gear?! Hahahaha


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[geeteeohguy]

40 years ago a friend built a '66 GTO with parts stripped off of a '70 HO 455 GTO. He rebuilt the 455 to a 462, retained the 64 heads, added an offy intake with dual AFB carbs, installed 4.56 gears in the 12 bolt, and ran the M22 Muncie. Getting on a freeway onramp, I was riding shotgun, and he nailed it in first or second gear and we sheared off most of the rear wheel studs. (Had Centerlines and N50-15's on the rear). After that he added aircraft grade studs and it held up. That thing would burn rubber at 55 MPH if you just goosed it in 4th gear. We cruised it up to an event in Sacramento, buzzing along at 50 mph the whole way, which wasn't TOO bad, as the speed limit back then was 55 and most went 60. Raced against a blown 454 '70 Chevelle and just cleaned his clock. Great times, but I would never have run that gear in that car. A 3.23 would have been perfect!!

[Tom Vaught]

Originally Posted by mgarblik

I had a 65 GTO tri-power close ratio Muncie with a 4.33:1 rear. I remember it being a 4 pinion unit when I had the cover off. It was my wife's daily driver for about a year. It was pretty miserable for her to drive, but she got the hang of it. The manual steering was more of a chore for her than the gearing. Federal speed limit was 55 when we owned it. So it was tolerable at 60 MPH. It was pretty punchy around town, but not a good choice for a Pontiac V-8. My friends 69 Ram Air III GTO was quicker in a street race. It had a 3.55 or 3.23 whatever was standard with a 4-speed. I was told the 65 came with the 4.33 ratio. Bought it from the original owner but no PHS back in those days.

When I was in college in the early 70s (for the second time, different state), the local speed limits in the city were in the 35 mph range. No need to go out on the expressway to run the car except to impress the ladies after coming back from the bar. One of the more stupid things I did in my early life.

If I went on a trip to Niagara Falls I swapped in the 2:56 rear for the mileage and lower engine rpm. Plus I could run 80+ on the 401 in Canada.
It just took a afternoon at the dealership to swap the rear end housings and reinstall the brakes. It was NOT fun to be going over 3000 rpm and barely keep from being run over by the trucks and buses, forget about the speed demons in the cars with a 4:33 gear on the highway (even when the speed limit, years later, was 55 mph.

Tom V

[PontiacJim1959]

I had a '67 GTO convertible with factory close ratio & 3.90 gearing. This was early 1980's and I was around 20. Speed limits were 55MPH. The car was pretty much done at around 100 MPH. It was a real mover and a blast, BUT, gas mileage was horrible and I had a $4.25 and hour job and had to drive to work 25 miles to and then 25 miles back home - and you know I was opening it up along the way. At around 10 MPG, the car was killing my paycheck. Out came the 3.90's and I think I put in 3.08's, maybe even lower, from a 2-speed 1965 GTO. Had great top end, but the gearing was too "stiff" and I went through a couple clutches in several months and in went an automatic. Didn't know what I had back then, just a fast GTO at the time.

So know that 3.90, 4.11, 4.33, 4.56's are great acceleration gears and more aimed for around town blasts, but you better have a thick wallet to feed them.

['ol Pinion head]

Racers running the 71 & 72 455HO A-bodys typically ran in NHRA E/S, F/S, G/S . Many ran 4.10 rear gearing, sometimes 4.33's in the car's 12 bolts with taller slicks.

In addition to an HO Formula, Truman Fields raced a strippo '72 455HO GTO in '72. Off & on over the years it had a set 4.10's in it. That particular '72 also had a set of boxed 4.33's that had been previously installed in the car when I carefully examined it. Was also able to test drive it, that was 8 or so years ago. The car had been owned by a friend of '77 Trashcan's. Richard owned it from the late 70's, until he sold it about 2013. From what was relayed, after being originally equipped with an M22, it was raced with a 2.88 first gear Power Brute T10...quite a bit stronger 4 speed transmission. Believe the PowerBrute was sold locally @ a swapmeet many years ago, as a turbo 400 & loose convertor had been installed in the '72. Really liked that '72 & its race history! In considering purchasing the '72, one of my issues was i couldn't get past the jade green interior,. The interior was in excellent condition & reflected the less than 4K miles on the car. If the car had a blue or covert colored fabric/vinyl bench seat interior, would have bought the '72.

The black/gold Monk King T-37 hardtop is another extremely low mile 455 HO lightweight. In its original XVK coded 12 bolt housing, it had 4.10's installed fairly early on. In the mid 90's I set up a set of thin Richmond 3.73's on a Brute Stength carrier for Mike M, the Moroso carrier may have been in it, I can't remember. That was while Mike owned & prepped the T-37 for its return to the 1/4 mile. That particular T-37 was originally raced in AHRA modified production w 455HO bottom end & a pair of '70 SR 614's. Believe a Nash intake, but not 100% on that detail. Mike put it back together with 197's, it ran quite strong mid to high 11's.

In the early 70's, my HO GT-37 had 3.73's installed in its original XVK housing. It was never upgraded to a Brute Strength carrier, stronger axles, & 4.10's. Have noted before, but if such rear upgrades had been made, I doubt I would have ever got a shot at buying the car. A shoestring budget of occasional racing eventually cultimating with breaking a stock axle & resultant LH 1/4 panel damage @ Tulsa relegated the GT-37 to be being towed several hours home. After installing another rear & being driven some locally, it was eventually parked in '78. I had one H of a time getting the original XVK rear reunited back in the GT-37 as it had been installed by the same owners in a 428 powered (rough)'68 GTO. That particular GTO had a somewhat colorful small town existence, but was not a RA car, & needed a ton of work. At the time, IMHO, it was not worth dumping a ton of money in. After purchasing the 68, it was eventually parted.

Also have owned one of the T-37 HO Coupes for many years. Of the eleven 71 455HO T-37 Coupes I'd hazard it was the heaviest one, as originally built. Not something I'm the happiest with, these cars are suppose to be light. Originally ordered out by Pontiac Engineering & sent to the GM Proving Grounds, it was ordered with over 30 factory options including M22, posi, AC, PS, R&H, 14" honeys, FM stereo, then a bunch of lightweight geegaw options. Oddly no power discs, but manual drums. While retaining the factory AC, I decided years ago to eliminate some extra weight for Pure Stock use, by substuting manual steering & alum front & rear drums. Have restored the original PS setup as well as original thick cast steel drums which do not take that long to swap over.

My take... quite a few of these '71 & 72 HO cars prepared for drag strip use early on.... thats when they gained these lower ratio gearsets. Some even received Service Package axles via Chevrolet high performance equipped dealership counters. Chevrolet high performance offered the 4.33 gearset as well as numerous other ratios.

[pokey1]

I bought my 67 GTO in 1976. Had a 400 with a muncie 4 speed with a 4:56 posi rear. Don't know how gears got there at the time. Was 16 at the time and thought it was the funnest thing to drive, could actually dump the clutch in 4th gear doing burnouts.. Hard on it I know now but was fun. Fortunately still own the same car but set up different now.

[Vid]

In some cases, the old adage of “Too much is just right” certainly applies, but in the case of rear end gearing I think I’ve just learned that “Too much is too much”. I think I’ll shop for something in the 3:56-3:73 range when I build my new rear. Seems like a good compromise that will have plenty of kick yet still be “somewhat” reasonable for limited highway driving. Thanks for all of your stories and comments, I learned a lot.


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[carcrazy]

Originally Posted by J GLASGO

What's info on that car?

I purchased it in September of 1973 from a Chevrolet dealership in Austintown, Ohio. Red with black vinyl top, turbo 400. Had 55k on it when I purchased it. Motor was rebuilt at 60k, balanced and blueprinted and some head work done by Valley head service. Spent a lot of time at Quaker City drag strip in Salem, NC. Can ran consistent 12.6 to 12.7. Sold the car in 1975 or 76 to purchase an l-79 66 Nova. From what I heard, the guy I sold it to blew up the motor within a short period of time. Should have kept track of the car but was fairly young and (dumb) at the time. Have no idea what the vin was.

[Mr Anonymous]

did pontiac ever use the W-27 aluminum axle section?

[mgarblik]

Olds had the death grip on that little nugget. From the factory, the strongest Pontiac rear ends were the 9.3 units used through 1964, and the 12 Bolt unit used extensively by Chevy and a few Pontiac's, in 1969-1970. My 70 1/2 TA had one.

[4zpeed]

I think that was a one year only, 1970 W27 Olds unit, and it was just the center section that was aluminum.


Frank

[MIAGIMAN]

My 70 unrestored RA IV has factory/build sheet 4:33 still in place, and going down the street/track is still a blast. When one ordered a car with those gears, he usually only had one intention and not to go cross country unless it was on a trailer!

[Tom Vaught]

Originally Posted by MIAGIMAN

My 70 unrestored RA IV has factory/build sheet 4:33 still in place, and going down the street/track is still a blast. When one ordered a car with those gears, he usually only had one intention and not to go cross country unless it was on a trailer!

I have driven a few RA-IV vehicles, 3 were modified, one was stock.
Never owned one. In a different life I would have sold my 64 GTO Convertible
4 speed Tri-Power like I did my 1965 GTO and 1966 GTO and bought the RA-IV
that was occasionally serviced by me at my Uncle's Pontiac dealership.

Have any pictures of that car you can post MIAGIMAN?

Tom V.

[MIAGIMAN]

Tom, I will give it a shot, if it don't work I will take some pictures when I get back home Monday. A little history on the car, a friend bought it new, arrived July 70, his brother bought the twin earlier in the year, both to race, one a auto the other 4 speed, my car won the summer nationals at E Town and runner up in the fall. The auto car was sold and from what I know was scraped eventually, When I purchased my car, included in the sale was the other RA IV drive train which I still have ready to install. Anyway in 08 I was asked to bring it to the GTO Nationals, with slicks, line lock electric pump it scored a gold in unrestored. John Sawurk loved it, the restorer Scott T. took some detail shots of unique factory details
I don't have to tell you a RA IV has a distinct sound and can pull some rpms. It also had 69 judge stripes on it when new that I will reinstall eventually

[Tom Vaught]

The 70 RA-IV was my favorite "later model" GTO.
At one time I had a 1970 Ram Air 4-SD FORGED Crankshaft made by Kellogg Crankshafts for PMD. That special crankshaft went into Marty Palbykin's 406 cid Twin Turbo car that today is being driven on the TV program Street Outlaws with a 482 cid engine.

Have you or anyone else ever heard of the RA-IV SD engine?

Tom V.

[MIAGIMAN]

I did hear about the SD rumors but never knew one existed. A funny story is when my 70 RA IV arrived at the dealership in Nyack NY they called Wayne and told him his car was in but it was sounding strange?? He drove down there immediately as they were getting ready to start taking it apart! They never heard a RA IV motor, they usually sold family cars! He took it home that day. I actually bought the brothers 64 GTO they raced and still have it 40+ years later. A 70 GTO has to be one of the best driving Muscle Cars I have owned