the time has come to decide what to do with the rear of my 65 442. should i rebuild with the factory housing or go another route? i am not planning on racing this car but i would like a nice medium between performance on take off and efficiency on the highway. the car will have a 400 engine with muncie 4 speed transmission. i am tearing down the housing now and will be dropping it off tomorrow to be powder coated the same time as the frame.

 

That rear should be more than adequate for your purposes. Check with @monzaz on here for gearing and Anti-Spin options if you want something other than what it's got.

Is the Muncie an M-20 or an M-21?

 

Factory rear will be great for any street use and any size motor.
As long as you stay out of chuck hole burn outs and silly stuff like bouncing off curbs etc. The stock rear with good upgrade after market parts will even do track time well.
REMEMBER:
A STICK SHIFT car can punish any size rear....it is up to you the customer to control yourself and be reasonable with clutch dumps etc. it is up to you how to treat your car...
I have see the 8.2 10 bolt do some amazing passes down a 1/4 mile with ridiculous power adders.
Build for what your going to do with the car.
Sounds like it one will be a fun street machine and it am sure as long as the parts are put together correctly it will do the job for a GOOD long time for you

Jim
JD Race

 

thank you, with today's supply chain BS, what would you recommend for parts? keep the original gear, which is supposed to be posi from factory, or replace everything? the car sat for 30 years, when i pulled everything apart, was pretty dark in there, the gear oil and sludged up on the bottom of the housing. there was no play in between gears and they appear to be pretty clean of any discoloration from overheating and no uneven wear marks.

 

 

IF you like the gear...(3.36) should be good for most driving applications still enough grunt but also capable to hit the freeway too .
THE posi unit is where you need to open up and see if the cones are bottomed out in theunit. IF they are we can machine the cones and towers etc. to make it live again.
BUT all NEW bearings and seal through out using all the same shims and pinion shim should be able to just put it all back together and not set up anything.
BUT you should always double check just to be sure .007 -.010 is a good range to be in. THE used gear will likely set up better in the .009 area
From the pics the gears look fine.
It appears that does not look like a POSI ... so you would need one of those if you want to leave 2 Black tire marks on the ground.

IF you do not do burn outs or spirited performance driving ...then LEAVE OUT THE POSI option...It is just a Noise maker for a driver like you.
Open diffs will always run quieter and less heat and less oil changes. LESS Maintenance period.

If you need to talk give a PM and I will get you my number.
Jim

 

Also note that whether the transmission is wide or close ratio should factor into your choice of a rear end gear. A 3.36 may be a little tall if you've got a 2.20 low.

 

thank you sir


i will have to call my friend with my transmission to find out but if 3.36 is a little tall with a 2.20, then that would be ok if i can cruise decent rpm's in 4th gear. a friend with a 2.20 4 speed and 3.73 gears says he was getting 3k rpm on the highway. he switched to a 5 speed and dropped down to 2k @60mph. i just remember the days of my first 65 that had the 2 speed and a 3.73 gear from the previous owner. i was screaming 3k+ on the highway, i'd like to avoid that with this car.

 

Top gear is the same (1:1) regardless of wide or close ratio 4-speed so cruising speed will be unaffected by which you have. Your friend's cruising RPM went down because he switched to an overdrive transmission.

Your concern would be the first gear ratio. My recollection is that the cutoff for factory availability of the M-21 close-ratio was 3.36, but that might be year-dependent. In your situation, you should hope you have an M-20 wide-ratio (2.52 or lower first gear) and look into swapping for one if you don't. With the original 3.36 rear, this should be a good compromise between a decent launch and having the car scream on the highway or a sluggish launch but tolerable cruising RPM.

 

65droptop - Only you know how much highway driving you'll be doing, and what RPM's you're willing to subject your engine and driveline to when doing it for extended drives. If you know the diameter of the tires you intend to use on your car, I would suggest using a RPM calculator like the one at the link provided below to find out the RPM's you'll be running in 4th gear (1:1) at various highway speeds.

https://www.strangeengineering.net/g...io-calculator/

 

thanks. i'm a true novice to some of this stuff, i understand how it all works, just never knew the formula, thank you i know that a friend of mine drives to Detroit for a big show every year in his 67 chevelle, i plan on joining him once my car is done. we live in northern ky and detroit is 4.5 hours of highway driving. i would probably drive to pigeon forge for the Rod Run, which is also about 4.5 hours. that would probably be the extent of my highway trips. olds nationals if there in TN would also be a trip i would take.

 

You're welcome, I hope it all comes together for you!

 

after talking with someone local that owns 65's, he said the 65 442 3.36 should be a factory posi rear? am i missing something?

 

I decided to go with a 3.55 gear.
But with my GV units .78 overdrive, I'll be at 2.76 final.
Kinda the best of both.

Are you sure you don't want a 5 speed?

 

I cannot definitively speak to '65 4-4-2's, but in the '67 4-4-2's (which I own) you only got the Oldsmobile Anti-Spin (posi) differential by ordering it as a separate option (G80), regardless of it being a 4-4-2 optioned (L78) car, and regardless of the gear set chosen. Mine is a 3.55 Anti-Spin unit.

 

Remember the camshaft profile will help the lower RPM torque kick in faster. MOST guys fail in the duration of the camshaft when picking a camshaft they always choose HP and forget where the torque comes in.
The more duration at .050 the higher the torque will start to produce good numbers in the torque also.
So what this means is 0 -3000 RPMs could be very sluggish until the cam starts to come into the power band. That is why BIG cams need the higher compression to make up for the lack of low end torque in the lower under 3500 RPM range of the motor...Then people use single plain manifold and then big carb then BIG headers ...ALL this slows down the air at lower RPM range. soooo you have to dump the clutch so high it is not a very good driving car...ALL or nothing mobile.

Just trying to help others in the thought process of building motors. Figure out what you want your vehicle to do and build the motor to do it .
HP numbers sell cars...TORQUE wins the race. Unless your using TURBO / superchargers and blowers....LOL

 

FYI, my '67 442 W30 came from factory with 3.55:1 rear and M21 muncie. The tires were F70x14 which are advertised as being 26.2 inches diameter. I never had any issue with having to "feather' the clutch with that set up, the low end torque of the 400 cube motor was quite adequate even with the W30 cam profile. As mentioned above you have to factor in tire size along with the other parameters. The muncie 4 speed trans (unless you purchase special gears from Auto Gear Equipment or other specialty shop) was only available in two gear ratio flavors from the factory, 2.20:1 1st gear (M21 & M22) or 2.52:1 (M20). The gear ratio spread from 1st to 2nd and from 2nd to 3rd is the same in all of them with a greater spread from 3rd to 4th in the M20. To change ratios you only have to change out the input (4th gear) and counter (most expensive) gear. Your 3.36 ratio rear is probably at the tipping point of drivability with an M21 or M22 muncie, especially so if you will have a larger tire! Regarding the 8.2 inch rear which was standard in all 1965 442s, it will be fine with street tires as long as you don't get crazy shocking it.

 

my 65 cutlass with factory M20 came with 3.23 gears from the factory

 

That's right, Stan, and I'm willing to bet you couldn't have got an M-21 with those gears.

 

any particular brand of posi units you guys recommend?