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3:91 + nailhead torque must really launch when it hooks up..................Wow!

It was in my '63 when I purchased it. The PO had it installed to raise the engine RPM's when he was towing his Airstream. Before that, he had burned a couple of valves by lugging the engine.

I've since but a 3.23 in it.

The car was my daily driver and I never really tried launching it with the 3.91 gears behind a Dynaflow.

I have the all the parts and think about putting it in my '64 behind a 200-4R transmission. That would give me the advantage of the 3.91 rear for "launching" then with the 200-4R's .67 overdrive, I'd have a 2.62 highway gear. Can I burn this candle at both ends?

Ed

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Been running 3.9 posi gears for a few years in my 64 Riv, great around town. The 64 posi center section is different from the 65. I currently have the 64 TH Trans, a 200-4R built to hold up to the torque and weight of a Riv would be great..

Roger

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a 3.91 rear end should be good for about 3000 rpm at 60 mph...

Stop light to stop light a Riviera out hurting guys tender little feelings.

My 66GS had a 3:07 open installed due to the PO's owners wife was deathly afraid of the 3:42 locking, the 3:07 would break loose quite often. I found a 3:42 in a wrecking yard, not only was the speedo correct once again that 3:42 would jump pretty good, I can only imagine a 3:91.

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It was in my '63 when I purchased it. The PO had it installed to raise the engine RPM's when he was towing his Airstream. Before that, he had burned a couple of valves by lugging the engine.

I've since but a 3.23 in it.

The car was my daily driver and I never really tried launching it with the 3.91 gears behind a Dynaflow.

I have the all the parts and think about putting it in my '64 behind a 200-4R transmission. That would give me the advantage of the 3.91 rear for "launching" then with the 200-4R's .67 overdrive, I'd have a 2.62 highway gear. Can I burn this candle at both ends?

Ed

Popular set up for a lighter car, not sure about a Rivi, but sure sounds nice.

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I was watching that auction to see if they sold. I'm sitting on 2 3.91 posi rears - have not tried them out ... yet. They are heavy - the Mopar guy that looked at it thought it was a Dana unit.

Very different from the 65 Riv and Wildcat 3.42 posi units from the Automatics. All the 4-speed cars seem to have the heavy unit.

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I was watching that auction to see if they sold. I'm sitting on 2 3.91 posi rears - have not tried them out ... yet. They are heavy - the Mopar guy that looked at it thought it was a Dana unit.

Very different from the 65 Riv and Wildcat 3.42 posi units from the Automatics. All the 4-speed cars seem to have the heavy unit.

Ted, I`ve come across both types in automatic cars. Probably just a matter of what was on hand at the time of build.

Tom

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So much for a 3:91 posi "rare as hens teeth" and for 1200.00 you still need a housing (no big deal on the housing) but need the axles too. Just my 0.02 a 3:91 posi w/o axles showing no excessive wear going for 750.00 would be fair to both seller and buyer.

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My car came equipped with the stock 3.07 rear, then the PO put the 3.91 in it. I took the 3.91 out and installed a 3.23; the only thing I could find at the time. Each of these swaps was done with the same axles. I seriously doubt if Buick changed the number of splines on the axles for different rear end ratios.

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So much for a 3:91 posi "rare as hens teeth" and for 1200.00 you still need a housing (no big deal on the housing) but need the axles too. Just my 0.02 a 3:91 posi w/o axles showing no excessive wear going for 750.00 would be fair to both seller and buyer.

Mike, The 3:91 gears are very unusual, Ted is an aggressive collector. Also, the carrier is a big deal because the performance gears (over 3:31) have a different carrier because of the thickness of the ring gear. In other words one cant use a 3:07 posi carrier and install a set of 3:91 gears. A spacer can be used but...

Tom

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  • 3 years later...
On ‎7‎/‎7‎/‎2014 at 5:14 AM, Ted "Wildcat65" Nagel said:

I was watching that auction to see if they sold. I'm sitting on 2 3.91 posi rears - have not tried them out ... yet. They are heavy - the Mopar guy that looked at it thought it was a Dana unit.

Very different from the 65 Riv and Wildcat 3.42 posi units from the Automatics. All the 4-speed cars seem to have the heavy unit.

Good afternoon.

 

Did you ever sell the 3.91's?

 

Thank you,

 

Marty

 

 

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Lol...Ted, I think it already is, but just to be clear, my description of you as an aggressive collector was intended to be complimentary. Quite honestly, I`ve never witnessed a collector visibly shake when there is mention of a 4 speed big car.....you know it`s true! Maybe someday I will graduate to "aggressive" status?!  :blink:

 

Tom

 

PS I miss the slammin gears emoji !

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Not only do I have 3.90's I also have a set of 4.45's. With the 3.90's launch is hard WITHOUT slicks. Good enough to pull the front L wheel. Would be GREAT with a 200R4. The 4.45's would be even better with a 200. Best time I have run so far is a 13.902@98MPH. Not too bad for 4400pds. & over 200K on the original engine.

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1 hour ago, telriv said:

Not only do I have 3.90's I also have a set of 4.45's. With the 3.90's launch is hard WITHOUT slicks. Good enough to pull the front L wheel. Would be GREAT with a 200R4. The 4.45's would be even better with a 200. Best time I have run so far is a 13.902@98MPH. Not too bad for 4400pds. & over 200K on the original engine.

Got any footage?

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On 5/4/2018 at 5:24 PM, 1965rivgs said:

Lol...Ted, I think it already is, but just to be clear, my description of you as an aggressive collector was intended to be complimentary. Quite honestly, I`ve never witnessed a collector visibly shake when there is mention of a 4 speed big car.....you know it`s true! Maybe someday I will graduate to "aggressive" status?!  :blink:

 

Tom

 

PS I miss the slammin gears emoji !

 

It is a perfect description, I had to laugh when I saw it...so true especially wen it comes to the 3 pedal Wildcats.

 

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                        I was visiting a farmer friend over the weekend to buy    a complete Riviera rear end with 3.91's in it that was sitting in his barn since 1967. While  I  

was there I bought one of his roosters to add to the flock in my hen house..................

hen's teeth.jpg

Edited by Seafoam65 (see edit history)
  • Haha 1
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