Vintage_barry

1966 Riviera differentials

Recommended Posts

I understand that the 66 Riviera GS had 3.42 Posi-traction.                                                                                                                                                           1st.- what was the standard 66 Riviera differential, 3.23? and was it a limited slip, Posi-trac?

2nd.- Could you purchase and change the rear gears 3.42 and achieve the GS stock results? I’ve seen them for sale from TA Performance $559.00.           Regards, Barry

Share this post


Link to post
Share on other sites

It's a GM "pos-traction" type with clutches and springs.  Here's a picture of a '67:

 

As far as swapping gears, (assuming you have the correct series carrier) the most difficult part is setting pinion depth and this can require specialized tools.  Then there's backlash and patterns.  Bearing preload if you've changed carriers or bearings.  It's not a casual endeavor.  I set-up a 12-bolt truck rear from scratch.  It took some patience.

DSC02322.JPG

  • Like 1

Share this post


Link to post
Share on other sites

I've never seen a PN code 3.23 in a 66 or 67 but imagine it could have been ordered. The shop manual shows the 3.23 was only available with limited slip. 3.07 was standard an was in the overwhelming majority of non-GS cars. A 3.42 ring gear will not work on a carrier for a 3.07. So when switching over from 3.07 to 3.42 the whole carrier is needed. 3.42 gear sets are not available in the aftermarket and generally folks who want to swap find an axle from a GS being parted.

 

The TA 3.42 gears you are looking at are for an 8.2 rear axle on the Skylark A-bodies. Rivs have a 9-3/8 Rear. 

Edited by JZRIV (see edit history)
  • Like 2

Share this post


Link to post
Share on other sites

1-NO, specialized tools are nec. & you NEED TO KNOW how to do the swap & the nec. procedures. It's not just plug & play. Most came with a 3.07 ratio. A change to 3.42 would need another carrier. A posi was an option & many DID NOT come with them.

2-T/A ONLY has gears for the 8.5" rears & not the 9 3/8" gears. The ONLY WAY YOU CAN GET THE 9 3/8" GEARS IS USED. 

A posi 3.42 complete can cost from $500.00-$800.00 + USED

  • Like 2

Share this post


Link to post
Share on other sites

I will add that 3.42s does more for a macho novelty to have vs real world driving enjoyment unless your goal is a fun fast 1/4 mile car then by all means they are great. 3.42s suck for open highway driving but that's just one opinion. 70-75mph puts the rpm range too high for my personal liking. The engineers knew this hence the reason for a larger diameter A/C compressor pulley on 3.42 equipped cars. 

I love the GS option but hate their highway driving manners with the 3.42. Admittedly 75% of my driving was open highway and realize many folks don't often drive their classics long distance.

In my opinion the switch pitch converter does a great job getting the car moving even with the 3.07s

Also you may or may not know the 66 GS had a BS code specific transmission with adjusted shift points. 67-70 all had same trans GS or not.

  • Like 2
  • Thanks 1

Share this post


Link to post
Share on other sites
6 hours ago, JZRIV said:

3.42s suck for open highway driving but that's just one opinion. 70-75mph puts the rpm range too high for my personal liking. 

 

I'll second Jason's opinion about the 3.42 gears and high speed highway cruising. I have a '65 Gran Sport with the 3.42's and it's great fun to drive around town, with  neck snapping performance off the line, and great toe-in response in suburban driving.  But on the highway above 60mph... Not so much.   The car has plenty of power to much faster, but the RPM's and attendant engine noise at cruise get wearing as one approaches 70mph and above.  On longer highway drives the car feels more comfortable when I keep the speed to around 60-65 and not more.

 

I agree that a better all-around rear end gear ratio would be the 3.07, or a 3.23 if you can find it.

Share this post


Link to post
Share on other sites

Agreed. AND, with 3.23 you don't need to change the carrier.

 

I rode around in my '64 Riv. I bought new in '64 with 3.90's for years. I driven fairly long distances with these gears but, nowadays being the older guy with gray hair driving at 55MPH in the 1st. lane you get the "Stares".  I'm doing more cruising than when I was younger & longer trips. The 3.07's the car came with are fine. For the longer trips I wouldn't mind 2.72's.

I also had 4.45's installed at one time. It wouldn't make it to the end of the 1/4 mile before it ran out of RPM's.  When & IF I build another engine to race it will be capable of 6500RPM's plus & the 4.45's will go back in.

 

Tom T.

Share this post


Link to post
Share on other sites

Yeah, I understand what you guys are saying. I didn’t realize the cons of a 3.42.   Now let me stir the pot a little bit. What would it take to convert from a 3.07 to a 3.23 limited slip?  Bad idea? Parts from other models available and functional?  Just asking, Barry

Share this post


Link to post
Share on other sites

Read my above post.    The Buick 9 3/8ths is ALL BY ITSELF. NO OTHER GEARS FROM ANY OTHER UNIT WILL FIT & FUNCTION.

  • Thanks 1

Share this post


Link to post
Share on other sites

Some more info here:

 

https://www.v8buick.com/index.php?threads/9-3-8-rear-differences.71740/

 

As others stated, the only parts that interchange with 9 3/8 is other 9 3/8.  The only market is used except for a stray NOS piece here and there...

 

Personally I wouldn't go through the work to change an existing rear from 3.07 to 3.23.  Not enough noticeable difference and anytime you change gears in a rear like this you need the specialty tools for setting pinion depth.  You might be better off looking for an entire differential with posi and gears you like.

Edited by RoadShark (see edit history)
  • Like 1

Share this post


Link to post
Share on other sites

Part of the "package" I'm considering for my '64 is adapting a TH200-4R to my nailhead.  I have all of he pieces for that.  The 200-4R is a .67 overdrive transmission which came from a mid 80's Oldsmobile.  (There are BOP and Chevy applications.)  The part of the package that I don't have but I'm considering is the use of a complete rear end out of a Ford Explorer.  It's a 8.8" rear end that basically the same as found in the high performance Mustangs. Not quite the beef as the Buick, but probably plenty for my use.  The thing that's most attractive for me is that it's the same width flange to flange and it is a posi trac unit (or whatever Ford calls it) and it's equipped with disk brakes.   It has a 3.73 gear ratio but that converts to a 2.49 highway gear when the trans is in o/d and the torque converter locks up.  I have all of the parts for a Scarebird front disk set up. Could be a comfortable highway ride if/when I get it all together.

Share this post


Link to post
Share on other sites

Here's a picture of a TH200-4r in a '65 Riviera chassis.  Not mine, but it belongs to a friend.  

 

No photo description available.

 

Modified OE transmission cross member 

 

No photo description available.

 

Other than this, it's pretty much a bolt in.

Share this post


Link to post
Share on other sites

I probably misspoke.  You need a different yoke on the front of the driveshaft; the St400 is SAE and the 200-4R is metric so the splines are different.  I don't know if you can do that with a U-joint or if you have to modify the driveshaft.  The owner didn't elaborate on this so it must not have been a big deal.

Share this post


Link to post
Share on other sites

Similar story for second gen Rivs. Shorten the drive shaft and move the crossmember. 

I have a 200-4R with a 3:42 posi in my ‘69. It works very well with my Stage 1 455

Share this post


Link to post
Share on other sites

It's unique to the Buick.  It has a 9-3/8" ring gear which is pretty unique in itself.  I tnink there are 14 bolts in the ring gear.  The only way to get a posi, if that's what you're after,  you'll have to find an original.  From the factory, most Rivieras came with a 3.07 gear ratio.  The number, unless someone has changed it, is stamped on the bottom of the housing.  The whole numer on one level, the decimal number below it.20150729_112714.thumb.jpg.aa6d74e99d174a83d3338e7cbcd33076.jpg

 

Here's a picture of the 3.07 under my '64

 

20150729_112620.thumb.jpg.c326b4bba660c9a4009337136ba541ff.jpg

 

On Sept 11, in the forum listing Rivieras on Craigslist,  I posted a link to a 3.07 posi for sale in the Kansas City area. That CL ad is stiil up as of today.  I couldn't post the link but it's in the post following mine.

Edited by RivNut (see edit history)

Share this post


Link to post
Share on other sites

I read an interesting article in an early 80's  car magazine I was looking at the other day that had been tucked away in my attic.

It seems that back in 65, a car magazine pitted a base 65 Riviera with a 401 against a 65 GS Riviera in a drag race to see how

much quicker the GS was. In their test, the GS outran the base Riviera but it took the entire quarter mile to do it. The 401 jumped out in front at the start

and it took a tad over a 1/4 mile for the GS to catch and pass the 401 car. Several passes were made with the same result each time.

My theory is that the 3.42 rear axle was holding the GS back. With all that torque the higher ratio rear end is faster.

  • Like 1
  • Thanks 1

Share this post


Link to post
Share on other sites
On 2/2/2019 at 4:27 PM, RivNut said:

Here's a picture of a TH200-4r in a '65 Riviera chassis.  Not mine, but it belongs to a friend.  

 

No photo description available.

 

Modified OE transmission cross member 

 

No photo description available.

 

Other than this, it's pretty much a bolt in.

Ed, any chance you could repost the photos? 

Share this post


Link to post
Share on other sites

I figured out how you can look at the pictures.  There is no description to go with them but there are enough for you to get the idea. In the Google search window, type in "1965 Riviera Facebook." The builder/author (Dave) has posted a lot of pictures of the build.  In the opening photo, you'll see a link for 'all pictures.' Do it.  Scroll through all of them.  There are pictures of the 200-4R in the chassis.  There are pictures of how all the parts go together.  There are a bunch of pictures of all the other cool stuff Dave fabricated as well as pictures of other cars he thought were cool.  Keep in mind that the pictures are not sequential, it's more like they go from finished product back to individual parts - they appear in reverse order. The pictures of the modified crossmember are not in the same area as the other transmission pictures.  Be sure to click on the link that will take you to page 2 of his pictures.

 

Ed

Edited by RivNut (see edit history)

Share this post


Link to post
Share on other sites

In reality the GS Riv. should be faster & ALSO because of the 3.42 gear ratio, BUT IS NOT. When you put your foot to the floor, WOT, with the 2x4 the intake manifold loses much of it's velocity which is what the "Nail" needs to help low speed power & breathing. At the top end the velocity starts picking up, BUT the 1/4 mile is over by then.

I remember back in 2000, 2001 when I went to Cecil County Maryland & there was a guy there with a modified '64 Riv. which had headers, 2x4's, a cam, etc.  Out of ALL the times we raced, which if I remember correctly, was something like 23 times, he was so frustrated most of the times I would beat him to the end. This is BEFORE my Roller Tip Rockers.

 

Tom T.

Share this post


Link to post
Share on other sites
1 hour ago, telriv said:

In reality the GS Riv. should be faster & ALSO because of the 3.42 gear ratio, BUT IS NOT. When you put your foot to the floor, WOT, with the 2x4 the intake manifold loses much of it's velocity which is what the "Nail" needs to help low speed power & breathing. At the top end the velocity starts picking up, BUT the 1/4 mile is over by then.

I remember back in 2000, 2001 when I went to Cecil County Maryland & there was a guy there with a modified '64 Riv. which had headers, 2x4's, a cam, etc.  Out of ALL the times we raced, which if I remember correctly, was something like 23 times, he was so frustrated most of the times I would beat him to the end. This is BEFORE my Roller Tip Rockers.

 

Tom T.

 

So whats the fix?

 

https://www.hotrod.com/articles/zero-to-hero-this-guy-reveals-dual-quad-tuning-secrets/

 

https://www.musclecardiy.com/performance/horsepower-secrets-intake-manifolds/

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now