69 8" Rear Options

[69volunteer 84]

I am finally to the point (not really as my other project is not done) of swapping out the rear of my 8" on my 302 with a C4. Current ratio is 2.79. I think I would go to a posi with 3:55 gears.

1-any thoughts on gear ratio, I RARELY get on the highway so top speed is 50-60 mph around town. however I don't want to be screaming at 3000 rpms on the rare occasion I do; but I would like to smoke the tires every once in a while. Is 3:73 too low?

2-prices on 3rd member units (and everything) have gone way up since I last looked; Ive seen some on EBAY but are these ready to bolt in or do I still need to set the pre load etc?

3-should i look to swap out the ring and pinion on my existing one (would probably have a shop do this); it wont have posi and will probably cost more, right?

4-i could post on FB to find some Ford shops that sell re-built 8" in Dallas (might be easier to go pick it up).

9" is not in the picture, I dont want to have to deal with all the other things that go along with that swap and I have a mild 302. Let me know everyone's thoughts.

 

 

[Len69Coupe 33]

Following. 

[Caseyrhe 650]

Swapping to a 9” is not all that difficult, can use same axles (if 28 spline), same brake lines, and same brake plates/hubs. 
The drive shaft will need to be shortened. 

if in Dallas, there is a man that comes up to Pate from Houston every year that has both 8” and 9” pumpkins that are quality rebuilt. Usually a month before he starts posting on C list. 

[rwcstang 201]

for your first question: what mods does your engine have? is it stock? Mild? Wild? it sounds like you may have a stock engine with some mods, but details would be great.

if you are worried about high RPMs, I would recommend 3:00 or 3:25s over 3:50's or 3:73's

I have a ford 9 with 3:50s Trutrac rear end with a TKO with 64 overdrive. I hit 2k at 65mph. I think with the c4 you'll be at 2200-2500k rpm depending on tire size. going 3:73 will raise your RPMs alot, unless you have a manual or Auto w/Overdrive.

I would use a rpm calculator to get an estimate.

2 - never bought from ebay, however there is one gent that sells 3rd members, I think some members on here have bought from him. https://www.ebay.com/itm/333955300971?epid=1717878485&hash=item4dc1497e6b:g:xRMAAMXQ0pNQ9gEa

3 - you can change out the gears, but you might aswell make it a posi unit, sure it'll be more cash but at least you did the swap all at once and didn't pay twice to remove it and upgrade. 

4 - if it were me, I would go with a full 9 conversion but a ford 8 can handle power. doesn't matter if its a ford 8 or 9 as long as the 3rd member and axles are upgraded with good parts.

5. I would also put a shift kit on your c4 with a 2500 stall convertor. this will give you the push you want aswell event if you stick with the 2:79 rear end.

 

 

 

 

[69volunteer 84]

5 hours ago, Caseyrhe said:

Swapping to a 9” is not all that difficult, can use same axles (if 28 spline), same brake lines, and same brake plates/hubs. 
The drive shaft will need to be shortened. 

if in Dallas, there is a man that comes up to Pate from Houston every year that has both 8” and 9” pumpkins that are quality rebuilt. Usually a month before he starts posting on C list. 

Do you know who the guy is? I havent been to Pate in a while. I assume C list in Parts?

 

2 hours ago, rwcstang said:

for your first question: what mods does your engine have? is it stock? Mild? Wild? it sounds like you may have a stock engine with some mods, but details would be great.

if you are worried about high RPMs, I would recommend 3:00 or 3:25s over 3:50's or 3:73's

I have a ford 9 with 3:50s Trutrac rear end with a TKO with 64 overdrive. I hit 2k at 65mph. I think with the c4 you'll be at 2200-2500k rpm depending on tire size. going 3:73 will raise your RPMs alot, unless you have a manual or Auto w/Overdrive.

I would use a rpm calculator to get an estimate.

2 - never bought from ebay, however there is one gent that sells 3rd members, I think some members on here have bought from him. https://www.ebay.com/itm/333955300971?epid=1717878485&hash=item4dc1497e6b:g:xRMAAMXQ0pNQ9gEa

3 - you can change out the gears, but you might aswell make it a posi unit, sure it'll be more cash but at least you did the swap all at once and didn't pay twice to remove it and upgrade. 

4 - if it were me, I would go with a full 9 conversion but a ford 8 can handle power. doesn't matter if its a ford 8 or 9 as long as the 3rd member and axles are upgraded with good parts.

5. I would also put a shift kit on your c4 with a 2500 stall convertor. this will give you the push you want aswell event if you stick with the 2:79 rear end.

 

 

 

 

Engine is 302 stock with a 351 cam. This is a sunday cruiser so I am not worried about the 8" being able to handle the power. I forgot about RPM calcs, that is a good idea. This is juvenile but considering that I rarely drive it on the highway I would opt for a lower gear. I know 9" is what everyone talks about but I really dont think it is necessary for me. Car was completely restored 8 years ago (wow, time flies) and gets driven a couple thousand miles a year (sad, I know). C4 was also rebuilt by a trans shop I use, I seem to remember a 2200 stall but could be making that up. 

Thanks for the replies. There is a DFW stang website plus FB and I will see if anyone recommends local rebuilder/seller.

[Caseyrhe 650]

No I do not, if my buddy still has his contact info I’ll pm you

[69volunteer 84]

thanks

 

[Rsanter 152]

First off, if it was me I would be shopping for whole 8” rear ends and try to find one that has the 325 or 355 gear ratio.

wont matter what car it came out of or what year as they are all 28 spline.

swap the center section and then I would resell the rear end with your gears in it

[69volunteer 84]

HMM....that is interesting. I like that idea.

• Doesnt that open a whole can of worms? Its been a long time since I dug into mine but I would want to replace axle bearings, gaskets, etc
• I would need to swap over all my new brake hardware
• More importantly, I thought there were different axle widths--or is that just 9" from later mustangs?

I like the idea as I would get a $75/core charge refund on my center section but maybe I could make more selling as a complete axle? Not sure it is really worth it though.

 

 

[rwcstang 201]

13 hours ago, 69volunteer said:

HMM....that is interesting. I like that idea.

• Doesnt that open a whole can of worms? Its been a long time since I dug into mine but I would want to replace axle bearings, gaskets, etc
• I would need to swap over all my new brake hardware
• More importantly, I thought there were different axle widths--or is that just 9" from later mustangs?

I like the idea as I would get a $75/core charge refund on my center section but maybe I could make more selling as a complete axle? Not sure it is really worth it though.

 

 

gotta search which ford 8 rears had 3:25'/3:50s, I think they are full size fords like LTD/fairlane/galaxie/ possibly mavericks and cougars. Im not sure which junk yards would have them since at least for me, junkyards near me do not carry old classic cars/parts anymore, just car from 80s - 90's + era vehicles. I would contact West Coast Cougar as they have a yard with old parts, maybe you can barter or buy a 3rd member from them.

you are correct that ford 8/9 had different axle widths, I think what @Rsanter is saying is find a complete used rearend with 3:25 and just simply swap out the complete 3rd member (pumpkin) and install it into your current rear end housing since its a direct swap and sell your old one in the other rear end housing since it is not a direct fit, or keep for storage if you have the space.

 

 

[BlueCoupe 8]

I've had good luck with Quick Performance out of Iowa. https://www.quickperformance.com/Ford-8-Inch-8-Ford_c_48.html

I got an 8 inch 3.55 truetrac third member and a 9 inch 3.70 truetrac third member from them.