1964 Thunderbird Rear differential

[Shadrack]

The driveshaft (if similar to mine) is connected by four bolts. The driveshaft has a double cardan joint on both ends with a circular flange on the end that connects to the rear. I believe either the flange on the driveshaft or the yoke is threaded for the four bolts which hold the driveshaft to the rear end (it’s been awhile since I did mine). It’s either that or there is nuts. Doesn’t matter which bolt goes where. Just take a paint pen and mark across the driveshaft flange and the rear end yoke. Now granted this is how it’s done on a 1969 Thunderbird. Your 1964 may very well have something different. Just get under there and look. As for rebuilding the rear? Make sure you have the right tools and a dial gauge to check for ring gear to pinion backlash and pinion depth. You can really mess things up if you don’t set it right. The old saying goes... “If it isn’t broke, don’t fix it.”

Been doing some research and finding all kinds of interesting things. My anniversary is coming up and she is really wanting a new phone, I found a "not pink," that is the color - Google Pixel 3 XL for my honey. I am thinking about asking her for a shop press, 20 tons to be exact. We have not gotten each other gifts in a LONG time and I think I could do some awesome stuff with a press. Including my wheel bearings, rear is what I have my eyes on now.

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[Shadrack]

So I have been eyeing kits. I figure if I am going to rebuild the suspension, I might as well dip my toes in and refresh the rear. What do you all think about this kit? It has a solid spacer in it which I hear is better of you need to redo preload as opposed to a crush sleeve which is one and done...but still reading on that - not sure. https://www.amazon.com/dp/B0078U8YHG/?tag=thunderbirdforum-20

I mean, if I mess up, worst case, I just have to start over or have it professionally done - where it is not my everyday car - seems like it would be okay :-D

I am open to suggestions about any other parts that would make it stronger than it currently is.

 

[Shadrack]

You might want to find out what gear you currently have.. I know a lot of the 64's had 3.00 gearsets. Without an overdrive transmission that is a pretty decent ratio. Go here https://www.randysworldwide.com/calculators/rpm , play around with this and see what changing gears will do to your RPM's at whatever speed you input.. If you do want to put more torque to the pavement you would want to go with a lower gear ratio, which is a higher number.. And as was stated before the Ford 9 inch is almost bulletproof.. Tough as nails and hard to destroy, although I did manage to shell the spiders in my 78 Bird..
Take Care
Ed

I am thinking 3.73 might be a good place. This car is for crusing at low speeds, will be off the expressway for the most part. I thought 3.73 would give me a good bunch and burn rubber. 🙂 Thoughts./

 

[OneAmongOthers]

I did’t need to change the rear gear. Gearing in mine is 2.88. Cruises fine up to 55-60 then the engine tends to rev a bit too high for my liking. However that’s a transmission issue not rear end. I myself did noting with my rear except replace the axle seals and had it sandblasted and I painted it myself with POR15. Other than than I just put it back together and filled it with oil. I honestly can’t give you much in terms of opinions on what gearing or parts you need to rebuild the rear. I was perfectly happy with the way mine works. As for suspension the rear is leaf not coils like mine. So not much I can give in terms of opinions there. I would say however to check for rot. Your era tbird was a unibody car so if anything is rotted out that could cause a serious issue.

 

[Shadrack]

I did’t need to change the rear gear. Gearing in mine is 2.88. Cruises fine up to 55-60 then the engine tends to rev a bit too high for my liking. However that’s a transmission issue not rear end. I myself did noting with my rear except replace the axle seals and had it sandblasted and I painted it myself with POR15. Other than than I just put it back together and filled it with oil. I honestly can’t give you much in terms of opinions on what gearing or parts you need to rebuild the rear. I was perfectly happy with the way mine works. As for suspension the rear is leaf not coils like mine. So not much I can give in terms of opinions there. I would say however to check for rot. Your era tbird was a unibody car so if anything is rotted out that could cause a serious issue.

Absolutely! So far she checks out pretty clean underneath. Most my rust is surface thankfully. I have one spring off and will get the other one in progress, have to start and stop a great deal. I just have a ton of oil and caked crap on the rear, my transmission pan seal is leaking, and of course my rear main. I'm trying to work my way up from the back to the front.

Im thinking 3.73 might be too aggressive thinking a tad under 3.50 or around there might pep her up and leave some nice tire marks

 

[Shadrack]

So, I am eyeballing this for overhaul: https://www.amazon.com/gp/product/B0078U7RQU/?tag=thunderbirdforum-20

I am also considering - gulp - this: https://www.amazon.com/dp/B0078U9TAM/?tag=thunderbirdforum-20

Lastly - https://www.amazon.com/dp/B00EHN3TVS/?tag=thunderbirdforum-20

What do you all think?

 

[biddle]

My mustang has a 3.55 and in sixth gear its 2200 rpm on the interstate. Im glad I didn't get the 3.73.

 

[Shadrack]

My mustang has a 3.55 and in sixth gear its 2200 rpm on the interstate. Im glad I didn't get the 3.73.

Awesome, I am thinking that the 3.50 +/- are the way to go.

 

[ak7an]

With the stock transmission 3.5 would spin your engine pretty high, even at 60 MPH..




If you are comfortable with that, then go for it. You would probably need that limited slip to hook the torque to the pavement. A 4r70, or E4OD conversion would be beneficial, then 3.73 or 4.11's would be great.
Take care.
Ed

 

[Shadrack]

With the stock transmission 3.5 would spin your engine pretty high, even at 60 MPH..

View attachment 5366


If you are comfortable with that, then go for it. You would probably need that limited slip to hook the torque to the pavement. A 4r70, or E4OD conversion would be beneficial, then 3.73 or 4.11's would be great.
Take care.
Ed

Yeah, I've been thinking about this a bit, hmm, wonder about some 3.23? Trying to find a happy medium. You can see I picked a posi diff, but looking for a little more tire burning power and torque, so thinking 3.23? I won't be on the highway a great deal but some.

 

[biddle]

Don't forget to order through our amazon link so we get credit for it to support the forum! You can click on your own amazon links as well one time only needed per purchase. https://bit.ly/ThunderbirdForum

 

[Shadrack]

Don't forget to order through our amazon link so we get credit for it to support the forum! You can click on your own amazon links as well one time only needed per purchase. https://bit.ly/ThunderbirdForum

I had no idea! I could have helped out a ton already lol. From here on out I will use it.

 

[mistfr]

My 61 has 3.50 gears and it has a sweet spot at around 50 mph (about 2000 rpm).
At faster speeds the engine really sound like it needs another gear in the gearbox.

I'm thinking about installing 2.50 or 2.75 gearing in a hope to move the sweet spot to around 60-65
and to utilize the 3 gears that my C6 have over a wider speed spectrum. I'll be loosing a bit of power
at the lowest gear but for my driving I don't think it matters much...

Just thought I'd add my 2 cents...

 

[OneAmongOthers]

My 61 has 3.50 gears and it has a sweet spot at around 50 mph (about 2000 rpm).
At faster speeds the engine really sound like it needs another gear in the gearbox.

I'm thinking about installing 2.50 or 2.75 gearing in a hope to move the sweet spot to around 60-65
and to utilize the 3 gears that my C6 have over a wider speed spectrum. I'll be loosing a bit of power
at the lowest gear but for my driving I don't think it matters much...

Just thought I'd add my 2 cents...

Stock in my 1969 Tbird is 2.88. At 60mph the engine purrs smoothly down the road. Anything higher and you need an overdrive. C6(comparable to the trans in the 64) was just not designed for modern highway speeds. Once you get over that its a fine tranny for cruising around. You also have to remember the transmission doesn't have a lockup clutch either so you will only get worse fuel mileage (as if it wasn't bad enough), as well as put excessive work on the torque converter and fluid at higher speeds.

 

[ak7an]

Stock in my 1969 Tbird is 2.88. At 60mph the engine purrs smoothly down the road. Anything higher and you need an overdrive. C6(comparable to the trans in the 64) was just not designed for modern highway speeds. Once you get over that its a fine tranny for cruising around. You also have to remember the transmission doesn't have a lockup clutch either so you will only get worse fuel mileage (as if it wasn't bad enough), as well as put excessive work on the torque converter and fluid at higher speeds.

I know if I was starting from scratch on a restore, an AOD or AODE from Monster transmissions would be top on my list. My 1964 has a Bauman AOD with 3.50 rear gears.. 2100 RPM at 70.. Very nice. From what I can research, most highway speed limits in 1964 were 70 MPH. Makes the 2.5-2.7 rear gear ratios that were available then almost a necessity. It is surprising that automatic OD transmissions didn't become the norm until the 1980's.
Take care
Ed

 

[OneAmongOthers]

I know if I was starting from scratch on a restore, an AOD or AODE from Monster transmissions would be top on my list. My 1964 has a Bauman AOD with 3.50 rear gears.. 2100 RPM at 70.. Very nice. From what I can research, most highway speed limits in 1964 were 70 MPH. Makes the 2.5-2.7 rear gear ratios that were available then almost a necessity. It is surprising that automatic OD transmissions didn't become the norm until the 1980's.
Take care
Ed

Eh I guess back then it was more about building cars with BIG engines and power for the track then something economic for highway cruising.