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1966 Riviera Overdrive


Riviman
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One of the more noticeable and enjoyable things about driving an old car, for me, is the lack of overdrive. The engine is always right there in the power band and responds so nicely to just a little nudge. A lot of times I drop my OD later model cars into straight drive for the last four or five miles because it feels so good.

My old car driving habits get me onto the secondary roads with quite a bit of that 45 MPH driving that OD doesn't like. Depending on the shift points and set up of a modern OD you could end up with the annoyance of the car downshifting if you just think about touching the pedal.

The Rivieras and smooth and feel great at 65 and 70, with another 40 or 50 MPH to go. I wouldn't change a car that has made so many people happy for 50 years. That's a nice drive train as is.

Bernie

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2 hours ago, Riviman said:

Has anyone installed an overdrive trans being a nailhead and if so how is it working out. Thinking of doing this upgrade. Any thoughts welcome...

There are a couple of these around.  From what I've learned you'll need to get the adapter, crank hub, and torque plate from Bendstens  I  Minnesota.  That adapter will bolt to the nailhead and you then bolt up any automatic that has a Chevy bolt pattern.  Don't go up in years so late that you get into computer controlled transmissions. That leaves you either a choice of the 700-R4 or the 200-4R.  The guys I know who have the 700-R4 says it's a really tight fit and the speedometer cable has to make a sharp bend at the X-frame.  Both need a TVC (throttle valve cable. ) Upshifts are handled via the cable's positioning of a valve which takes the place of a vacuum modulator.  A quick trip around the block WITHOUT the cable will burn up the trans.  Both transmissions will need some "beefing up" to handle the torque of the nailhead.  The 200 is an unsung hero.  It's the transmission that Buick used in the ultra fast Regal GNXs so it can handle anything you want to drive on the street.  The 700 has a .7 overdrive and the 200 has a .67 overdrive.  The 200's gear splits are very close to ST400 that was original; the 700 has a really low numerical 1st gear which renders it almost useless with a high torque low rpm engine.

 

Ed

 

PS - you can buy a lot of fuel for what it costs to perform this swap.  

Edited by RivNut (see edit history)
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3 minutes ago, RivNut said:

There are a couple of these around.  From what I've learned you'll need to get the adapter, crank hub, and torque plate from Bendstens  I  Minnesota.  That adapter will bolt to the nailhead and you then bolt up any automatic that has a Chevy bolt pattern.  Don't go up in years so late that you get into computer controlled transmissions. That leaves you either a choice of the 700-R4 or the 200-4R.  The guys I know who have the 700-R4 says it's a really tight fit and the speedometer cable has to make a sharp bend at the X-frame.  Both need a TVC (throttle valve cable. ) Upshifts are handled via the cable's positioning of a valve which takes the place of a vacuum modulator.  A quick trip around the block WITHOUT the cable will burn up the trans.  Both transmissions will need some "beefing up" to handle the torque of the nailhead.  The 200 is an unsung hero.  It's the transmission that Buick used in the ultra fast Regal GNXs so it can handle anything you want to drive on the street.  The 700 has a .7 overdrive and the 200 has a .67 overdrive.  The 200's gear splits are very close to ST400 that was original; the 700 has a really low numerical 1st gear which renders it almost useless with a high torque low rpm engine.

  Great reply Ed, you have obviously done some homework.

  The only thing I`d like to add as an overall consideration  is with the overdrive gear one can go to a higher numerical rear diff gear, like a 3:42, and still have a comfortable driving car at today`s highway speeds which can regularly exceed 70 MPH or more. Every 3:42 geared GS I have owned gets "twitchy" at about 65 MPH and tended to be fatiguing to drive for prolonged high speed highway driving. Just another consideration regarding an OD swap...

  Tom

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I have every thing to do a 200-4R swap and a 3.91 rear end to go with it. That rear gear with a .67 overdrive will still give me a final drive ratio of 2.62.  With a 225/75r15 tire that calculates to about 1800 rpms at 70 MPH.  

 

One thing I forgot to mention is that both transmissions have lockup torque converters. This will also pull your rpms down.  I think that with a 3.07 rear end and an overdrive transmission  you'll be taking the engine out of its comfort range. That would give a final drive of about 2.04.  Pretty low.

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1 hour ago, 1965rivgs said:

 Every 3:42 geared GS I have owned gets "twitchy" at about 65 MPH and tended to be fatiguing to drive for prolonged high speed highway driving. Just another consideration regarding an OD swap...

  Tom

Indeed. I despise the 3.42s for interstate driving and can understand why Henry is looking for relief in the form of an OD. I was very close to swapping in a set of 3.07s in my old 67 GS because most of my driving was open highway. 

Agree the OD would surely be nice in a GS with 3.42 rears but not sure the amount of work and expense involved would provide enough benefit unless you are driving the car often or have other modifications. An option would be swapping to 3.07 gears as they are easy to come by. To me 3.07s always seemed to cruise 75 mph nicely and there were times when I sustained 85 mph for many miles. A small sacrifice will be made off the line but you might be surprised how little difference the 3.07 equipped car will be be off the line due to the switch pitch converter.

 

Henry - Check out article by Ed Raner and Dave Gee Riview Volume 26 #4 page 6 and 7. It covers adding OD in a first gen. Also check Volume 20 #3 page 11. And then Volume 18 #2 page 9/10.

 The latter 2 article are geared more towards the 430-455 but outlines similar obstacles that will need overcome on the 66.

Edited by JZRIV (see edit history)
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Not unlimited but... a 225/75R15 tire is 28.3 inches in diameter.  According to an online speed / rpm calculator that tire with a 3.07 rear gear and a .67 final transmission gear would give you just a hair over 184 MPH @ 4500 rpm (pretty doable for a nailhead) But you need to take into consideration horse power to over come drag.  At 8000 rpm, the speed is right around 347 MPH. I don't think that any chassis parts, tires, or whitey tighties would survive that.

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Just swap out the gears, the kind of life those cars live today is nothing like the 1966 buyer would have subjected them to. All mt stuff sees 65 to 85 MPH driving, but with annual mileages of 1200 on the high one and 500 at the lowest, not even a 50 mile one-way drive to a cruise night got tedious when I had my '56 Willys 4WD pickup. And that drove like farm equipment.

 

If you want a taste of modern overdrive, multi-speed transmissions try out a late Cadillac STS with a V8 in varied suburban traffic. You will really smile when you get back into your Riviera.

 

There is one drive train modification I have given serious thought to over the years. I like shifting and winding our through the gears but always skipped the 1-2 shift on 4 speed cars I had. I just took off in second. On my '64 Riviera I have contemplated a Chevy close ratio 3 speed. The short tailshaft would fit well and it would give "me" the same performance of a 4 speed the way I drive. And that would just be for the pure audio pleasure of the exhaust. I know I can get all the parts new.

Bernie

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I got 2 years and about 12,000 miles on my gear vendors overdrive with (3.07 gears final drive is 2.39).  I is wonderful to drive at highway speeds and with the nailhead torque I can be in overdrive at 25mph plus with the miles I'm driving I think there will be less wear and tear on my engine over the long haul.  (I use my 64 Riviera to go to work on nice days which is over 40 miles both ways.

 

That being said, the job to install it is not for the faint of heart.  It's a lot of work.  But the winter's are long in Ohio and I have a nice heated garage so that's when I did the project. 

 

 

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1 hour ago, Wildcat65 said:

Russ Martin @ http://nailheadbuick.com/  is selling a bellhousing that enables one to bolt a 4L60 to the Nailhead.

I like it because it reduces the length of the trans, which may be a difficulty in the X frame cars installations.

Russ is a distributor for Bendstens.  The 4L60 is the computerized version of the 700-4R.  They're identical dimensionally.  The 4L60 uses a computer to control it vs the TVC (cable between the throttle linkage and the valve in the transmission.)  The 700 is 100% mechanical.  So unless you want incorporate a computer into your system, go for the 200-R4.  The one person I know who did install a  700-4R had to do some "hammer massaging" to the tunnel to make it fit.  He's also the one who had speedometer cable issues.

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Sorry, if you look at Russ's site you would see the bellhousing I'm trying to describe.

It replaces a removable bellhousing on 4L60 

 

Beautiful clean looking trans adapter, put a 4L60-E from a 98-99 1500 GM truck or a 98-02 Full size van with 4.3-5.7 Engine. 575.00

..We have flywheel covers and flexplates available. No crank spacers or missing bell housing bolts like other adapter. More floor clearance in small hot rods.

 

 

4l60.JPG

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4 hours ago, rapom said:

I got 2 years and about 12,000 miles on my gear vendors overdrive with (3.07 gears final drive is 2.39).  I is wonderful to drive at highway speeds and with the nailhead torque I can be in overdrive at 25mph plus with the miles I'm driving I think there will be less wear and tear on my engine over the long haul.  (I use my 64 Riviera to go to work on nice days which is over 40 miles both ways.

 

That being said, the job to install it is not for the faint of heart.  It's a lot of work.  But the winter's are long in Ohio and I have a nice heated garage so that's when I did the project. 

 

 

You were able to get the GV in with the X-frame?  I'd love to hear more about this.

 

I emailed GV for dimensions on the their shorty unit and they didn't even respond when I mentioned the X-frame.

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9 minutes ago, Wildcat65 said:

Sorry, if you look at Russ's site you would see the bellhousing I'm trying to describe.

It replaces a removable bellhousing on 4L60 

 

Beautiful clean looking trans adapter, put a 4L60-E from a 98-99 1500 GM truck or a 98-02 Full size van with 4.3-5.7 Engine. 575.00

..We have flywheel covers and flexplates available. No crank spacers or missing bell housing bolts like other adapter. More floor clearance in small hot rods.

 

 

4l60.JPG

I looked the website but didn't see this one.  Sorry.  I'm wondering if it would also work with a 700R-4? That trans body is still bigger than a 200-4R and would be a tight fit.

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5 hours ago, RivNut said:

 I'm wondering if it would also work with a 700R-4? That trans body is still bigger than a 200-4R and would be a tight fit.

 

The bellhousing only works with the later 4l60E that has a removable bellhousing.  700-R's have the integral housing.

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Gear Vendors told me that I'm about the only person install the unit in a 1st. gen Riv.   They wanted my pictures so they could see how I did it.  Check out the link for more info and pictures.

 

If my Riviera was a lot nicer, I would have probably went the 200 4r route.  

 

You may have more x-frame room than I did, if you have a 66-67

 

http://forums.aaca.org/topic/269952-torque-is-torque-is-torque/#comment-1459896

 

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With a nailhead, I would tend to change the rear end gear set before giving up the 400 transmission. I wouldn't even attempt the purchase/installation of a Gear Vendors on my '66 Riv. I have the complete banjo off a '70 Electra with a 2.56 ratio that I was going to do a swap with one my Wildcats 'one of these days', but that day hasn't happened yet!  My old hauler El Camino has a 2.41 ratio and the early fuel injected 3.8 Buick with the 4spd overdrive in our '85 Olds Ciera wagon ended up at 2.29 =both did very well on the road.        Dan   Mpls. Mn.

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I'm no transmission expert but Russ's site tells you exactly which transmissions will work. Don't get the 4L60 and 4L60E confused, different transmissions. 4L60 I believe was the mechanical later version of 700R, 4L60E the electronic (computer controlled) version.

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Some time ago, I saw an article that showed the installation  of a GV overdrive unit in an antique Cadillac.  It showed the installation in the middle of the driveshaft.  Just curious if one could be put behind the X member in an early Riviera.

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GV unit would probably need to be floating.  There would be too much binding if it were fixed as the driveshaft would be way to short. (With dual cv joints there would hardly be a driveshaft.)

 

I just had the driveshaft out yesterday for it's annual lube so it I can easily visualize that it wouldn't work without major fabrication.

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On 2/1/2017 at 2:38 PM, RivNut said:

Some time ago, I saw an article that showed the installation  of a GV overdrive unit in an antique Cadillac.  It showed the installation in the middle of the driveshaft.  Just curious if one could be put behind the X member in an early Riviera.

Since this is somewhat speculation- If you look at a first generation frame without the rear suspension the size and shape look like it would accept a Jaguar XJ series rear subframe and rear end assembly. You might even be able to use the original Jaguar mounts. The movement of the whole set up is minimal. Put the OD in the cubby the rear Y makes.

 

If you are going to do it, get the IRS and inboard rear discs too.

Bernie

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