[Tomaso]

Hi Guys,
Hopefully this is the right place to post this thread question. Looking to upgrade and get a stroker crate motor or have mine rebuilt. With around 550 ft.lb of torque. Looking to place in the 66 Bonneville. It's going to be for the street, not really strip.
Just wondering now, what else would you recommend he upgraded? Brakes are done.

1) I would be having the TH400 trans rebuild to handle that..
2) does the frame need to be reinforced?
3) would like to upgrade to posi and 3.55 gears. But will the 8.2 rear differential hold up? Or do I need to upgrade to 12 bolt(not sure how easy it is to find one where I am)
4) upgraded cooling system.

What else would I be looking at and what would you recommend? Thank you

Thanks.

[Scott Stoneburg]

You wont need to do any frame strengthening, you can get good parts for the rear to handle that much power. I would also look at suspension upgrades depending on what the intended use of the car is. Drag race, road course or just daily driving. Look at shocks, sway bars etc..

[AZ64GP]

1) You can definitely have your TH400 rebuilt to handle that torque. The TH400 is a tough transmission and can be built to handle much more power than that and drag race duty.
3) I think as long as you drive the car on the street and don't beat on it, the stock rear end will hold up. If you think you're going to be hard on it or maybe hit the strip, you'll want something strong. I don't know about parts availability in Canada, but I know that a lot of 12 bolt rear ends are getting hard to find for passenger cars in the US. If you really want to upgrade your rear end, you are probably better off putting a Ford 9" in it.

[Tomaso]

Thanks guys, again for street. I doubt I will be taking it to the strip. I was thinking of rebuilding the 8.2 I had as long as the new parts can handle that torque (maybe more) if need be...
Shocks Ive replaced.
I’ll take a look for a sway bar.

[Goatracer1]

The rear end is not the same as a Tempest/GTO and I think you will have a hard time finding parts for it. Your best bet would be to find a Ford 9" rear close to the width you need and have the mounting brackets swapped from yours to fit. You can then get parts cheap for that for any ratio and limited slip you want. There were dozens of Ford cars and trucks that used them so finding one in a junk yard should not be hard. Some Mercurys even had 5x5 bolt patterns. Otherwise you can have the axles redrilled or get stronger axles in your bolt pattern if you want.

[Schurkey]

How long the rear axle lives is going to depend on how sticky the tires are, and how "developed" the suspension is. In other words, "traction"..

If you've got enough traction, that axle is doomed. If you're just spinning tires, it'll likely live at least for awhile. "I" would be very reluctant to throw money at an 8.2.

Yes, upgrade the cooling system.
Yes, upgrade the suspension
Yes, upgrade the steering
Yes, replace the body-to-frame mounts.

What do you mean by the brakes are "done"? A stock rebuild is not going to be good enough.

[Tomaso]

Originally Posted by Schurkey

How long the rear axle lives is going to depend on how sticky the tires are, and how "developed" the suspension is. In other words, "traction"..

If you've got enough traction, that axle is doomed. If you're just spinning tires, it'll likely live at least for awhile. "I" would be very reluctant to throw money at an 8.2.

Yes, upgrade the cooling system.
Yes, upgrade the suspension
Yes, upgrade the steering
Yes, replace the body-to-frame mounts.

What do you mean by the brakes are "done"? A stock rebuild is not going to be good enough.

Will be buying the front disc conversion for the Bonneville.
What should I be looking at upgrading for the steering?
Should I go for the Ford rear?

[Schurkey]

Originally Posted by Tomaso

Will be buying the front disc conversion for the Bonneville.

"The" front disc conversion? There is only one? Not likely. Look at options, find something that's going to stop that much power.

Originally Posted by Tomaso

What should I be looking at upgrading for the steering?

At minimum, replace everything that's worn-out, and upgrade the steering box to faster ratio/larger torsion bar. Be sure to retain the same turn radius. "Performance" front-end alignment.

Originally Posted by Tomaso

Should I go for the Ford rear?

Very popular as far as replacement axles go.

I have a prejudice against Ford parts on my GM cars, but that's probably silly since the aftermarket makes "Ford" axles without a single OEM Ford part in them.

Just be aware that there's other choices. GM "corporate" 8.5, Dana 60, Chevy "12-bolt", Mopar 9 1/4, Chevy Truck 14-bolt semi-float, Mopar 8 3/4...there's LOTS of choices; and none of them except the 12-bolt will be usable without mods. Finding a 12-bolt to fit a Bonneville is unlikely; so expect to have someone doing some welding of spring perches, shock mounts, cutting for overall width, etc.

[Goatracer1]

Ford 9" is your best choice. Mopar 83/4 in a width you need will be hard to find. Dana 60 is a great rear end but very heavy and beefier than you need. Don't waste your time installing a heavy duty truck one. Chevy 12 bolts for a full size car are also hard to find. Again, if you decide to change your's there are many Ford 9" to choose from and lots of parts for them.

[Tomaso]

I think I will stick with the 9 ford. I found on a website a complete set up? Comes with the ford 9, as well as disc brakes on it too. Also as choice of 3.50 or 3.70 gears or some others as well It’s expensive but comes as a whole rear end. Would that be good enough?

Out of curiosity, how much HP/torque can the frame handle without doing any modification to it?

[lust4speed]

Might be a good time to point out that the big car rearend is a stout unit and has an 8.875" ring gear the same diameter as the Chevy 12-bolt. While the ring gears are the same size, the only interchange item is the clutch pack as far as I know. Axles are 31 spline and larger than the 12-bolt 30 spline. Fabcraft is out of their 3.55 ring and pinion but I believe will be eventually starting another production run. The Fabcraft ring and pinion was designed to bolt up to the 2.73-3.08 carrier, and you have to use the 71-76 31 spline big car pinion yoke.

While Pontiac produced a lot of 3.42 ratios, the 3.08's and higher will be more numerous. The big car unit has 10 bolts holding on the cover but 12 bolts securing the ring gear.

The '65 and '66 frames were all boxed and you are not going to hurt a non-rusted frame.

[Tomaso]

Originally Posted by lust4speed

Might be a good time to point out that the big car rearend is a stout unit and has an 8.875" ring gear the same diameter as the Chevy 12-bolt. While the ring gears are the same size, the only interchange item is the clutch pack as far as I know. Axles are 31 spline and larger than the 12-bolt 30 spline. Fabcraft is out of their 3.55 ring and pinion but I believe will be eventually starting another production run. The Fabcraft ring and pinion was designed to bolt up to the 2.73-3.08 carrier, and you have to use the 71-76 31 spline big car pinion yoke.

While Pontiac produced a lot of 3.42 ratios, the 3.08's and higher will be more numerous. The big car unit has 10 bolts holding on the cover but 12 bolts securing the ring gear.

The '65 and '66 frames were all boxed and you are not going to hurt a non-rusted frame.

Thanks Mick, so am I safe to build this rear that I have? I was going to order a new Yukon posi and 3.55 gears for it?

[lust4speed]

Only reason I wouldn't use the Pontiac rear is if the final cost of finding a limited slip unit and the gears along with the normal rebuild (freshening) was approaching the cost of ordering one out. Last December I ordered out a Strange Dana 60 for my 67 GTO and with their current sale and free shipping the cost was under $2,800. Both strange and Moser build new Dana 60 cases and the overall width can be chosen when ordering. The cost of the 60 was less than their 12 bolts and the same as the 9" Fords. Know I'll get some heat for the photo but took this pic at the Hotrod anniversary drags at Pomona awhile ago. Second time I've seen it happen at the drags with a 9".

Anyway, I've got the Fabcraft gears and a 1965 3.08 Pontiac posi rearend and it's going in the '65 Catalina Safari wagon that will have 495ci of push.

[Stuart]

Originally Posted by Tomaso

Thanks Mick, so am I safe to build this rear that I have? I was going to order a new Yukon posi and 3.55 gears for it?

Yukon's website indicates the limited slip unit they sell for big Pontiacs is the same 8.2" one they sell for A and F body cars...I'd call them to make sure what they're selling will actually work in a Bonneville.

[Schurkey]

Originally Posted by Tomaso

how much HP/torque can the frame handle without doing any modification to it?

NOT VERY MUCH until you replace the body-to-frame bushings.

Originally Posted by lust4speed

The '65 and '66 frames were all boxed and you are not going to hurt a non-rusted frame.

I was astounded at how flexible and weak the frame is. The body has most of the strength. Until the frame is fully attached to the body, the frame is a weak-ass piece of crap.

This coming from a guy with a "fully-boxed" '68 El Camino frame. I could flex the rear section by pulling on it with one hand once the body mount was removed.

I have no illusions about the "B" body frame being more structural than the "A" body frame. The frame is different, but the concept is the same--the body does most of the reinforcing, the frame is just a convenient "bracket" to bolt the suspension and steering to.

Replace the body mounts so the frame and body are properly coupled, and the whole car handles better, rides firmer, and doesn't rattle as much. Even "new" rubber bushings would be an improvement; although I used Polyurethane. And, of course, non-rusted hardware as well.

https://www.chevelles.com/techref/body_bushings.html

Originally Posted by lust4speed

Might be a good time to point out that the big car rearend is a stout unit and has an 8.875" ring gear the same diameter as the Chevy 12-bolt.

He says he has an 8.2. The vehicle came with an 8 7/8?

Originally Posted by Stuart

Yukon's website indicates the limited slip unit they sell for big Pontiacs is the same 8.2" one they sell for A and F body cars...I'd call them to make sure what they're selling will actually work in a Bonneville.

ABSOLUTELY. You need to figure out "WHICH AXLE DO YOU REALLY HAVE"? I was wondering about Pontiac using an 8.2 in a Bonneville. A Biscayne with a 283--sure. Bonneville? Doesn't seem reasonable, but what do I know?

[ben3843100]

I just wanted to point out that not all 1966 Pontiac (US-market) b-body frames were boxed. Without looking it up, I believe all convertible frames were boxed, but boxed frames on other b-bodies were a factory option. I can’t speak to the Canadian cars using Chevy running gear since they are a completely different animal.

-Ben


Sent from my iPhone using Tapatalk

[mgarblik]

Originally Posted by lust4speed

Might be a good time to point out that the big car rearend is a stout unit and has an 8.875" ring gear the same diameter as the Chevy 12-bolt. While the ring gears are the same size, the only interchange item is the clutch pack as far as I know. Axles are 31 spline and larger than the 12-bolt 30 spline. Fabcraft is out of their 3.55 ring and pinion but I believe will be eventually starting another production run. The Fabcraft ring and pinion was designed to bolt up to the 2.73-3.08 carrier, and you have to use the 71-76 31 spline big car pinion yoke.

While Pontiac produced a lot of 3.42 ratios, the 3.08's and higher will be more numerous. The big car unit has 10 bolts holding on the cover but 12 bolts securing the ring gear.

The '65 and '66 frames were all boxed and you are not going to hurt a non-rusted frame.

Thank you for clearing up that common misconception about the 65-70 full size Pontiac rear ends for the OP. They are plenty strong for what the OP plans to do IMO
As you said, the ONLY problem is parts. They are hard to come by and pretty expensive. As far as a rebuild, you can use the Eaton limited slip rebuild kit clutch kit for the later 8.5 axles. The press-on axle bearings are a weak point and are available, case and pinion bearings are available. Side gears, spider gears, case and ring and pinion gears are available used only and hard to find. If you have a rear in good working condition, I would freshen it up as needed and run it. I raced these rear ends with 3.42 and 3.73 ratios, with 4-speeds and radials as well as small slicks for years and hundreds of runs without breaking anything.

Concerning the frames: I don't think all the full size cars were fully boxed. I could be wrong, but pretty sure only the convertibles and the Grand Prix had a full boxed frame all the way down. I believe the others had open "C" channel sides and were semi boxed in other stress areas. Still think they are plenty strong.

[misterp266]

I raced a ‘66 GP for years with that rear end. Ended up with 3.42’s in it with hundreds of runs on some small slicks. 12.10 @ 110 with a 1.60 short time. They are strong but, you can’t get parts anymore. And yes, my GP had a full boxed frame.

[63gpman]

Never confirmed but was always told that GP and verts were all boxed. You could check the box for hd frame though. My 65 4 speed car has a boxed frame. I have never ordered PHS to see how that was ordered though.

Yes, 8.875 rear in these. 10 bolt cover 12 bolt ring. Many places mess up interchange because the grand prix was a b-body till 69 so they see GP interchange with GTO and expand the years .

[lust4speed]

Here is a quote from page 1A-2 of the 1965 Pontiac Chassis Service Manual:

"The convertible, hardtop, 124" wheelbase sedan, station wagon and Grand Prix frames are essentially the same as the other corresponding wheelbase frames but have the center side rail fully boxed for additional stiffness."

I think that really only leaves out the 2-Dr Catalina coupe as having an un-boxed frame? 124" sedan would include 4-Dr Bonneville and 4-Dr Star Chief post models. Isn't the GP frame the same frame as the 2+2 and Catalina 2-Dr HT?

My 65 2-Dr HT Bonneville, 65 4-Dr Star Chief Sedan, 65 Catalina Safari, and my son's 65 2+2 all have boxed frames and fit the above quote.

I've been gathering parts and have a stock 65 3.08 limited slip rearend, Fabcraft 3.55 gearset purchased several years ago, and just recently purchased the Fabcraft master rebuild kit along with a chromoly 1350 yoke. Parts were not cheap, but will still only have about 1/3 the price of a ready-to-install rearend from Moser, Strange, or Currie. It will still be a step down from a monster build aftermarket unit, but should be up to the task since a bone stock 3.42 rear has held up to 20 years of street and dragstrip abuse in the 2+2 under our ownership.