Local 3.5 gears

[PeteG41]

Found these for sale locally. Apparently taken Out to change the ratios, no more than 1k miles on them. Up for $100. I was going to do 3.5 gears with my rebuild, worth taking a flyer on these?

 

[Sheriff41]

I always use a new gear set when I do a gear change. Too much work to take a chance on used gears. That said, someone who does gear installs frequently may be able to tell you if the gear set is good or not.

 

[PeteG41]

I always use a new gear set when I do a gear change. Too much work to take a chance on used gears. That said, someone who does gear installs frequently may be able to tell you if the gear set is good or not.

Thats kind of what I was thinking as well, but this is a new area to me so wanted to ask the ones with experience. It would save me about $250 compared to a new set, but in the long run is that worth it not having the peace of mind that I am starting new.

 

[Sheriff41]

Check prices with these shops:
https://8and9inchfordrears.com/https://www.quickperformance.com/
I'm running a Quick Performance set up in my 72 with no issues.

 

[PeteG41]

Check prices with these shops:
https://8and9inchfordrears.com/https://www.quickperformance.com/
I'm running a Quick Performance set up in my 72 with no issues.

Awesome I'll check them out!

 

[PeteG41]

Check prices with these shops:
https://8and9inchfordrears.com/https://www.quickperformance.com/
I'm running a Quick Performance set up in my 72 with no issues.

https://www.strangeengineering.net/product/us-strange-gear-ford-9-3-50.html/
https://www.summitracing.com/parts/rmg-f9350/make/ford/model/mustang/year/1973
Looks like I found exactly what I needed, but feel free to check my work!

 

[mrgmhale]

The prior owner of our 73 Mach 1 changed out the original 2.79:1 rear axle gears for a 3.5:1 TractionLok set of gears. The result was him getting some very snappy low end performance with the street/strip 351W (not C) he replaced the original 302 engine with. Frankly, for a vehicle that will be driven on the street, the lowest gear ration I would suggest is 3.5:1. And, if you plan to do any zipping around and Wide Open Throttle launches, I would go the added step and get a TractionLok rear axle gear set, otherwise you will end up frying either one rear tire or the other upon heavy burnout on spirited launches with a 3.5:1 rear axle ratio.

Now for the practical side of the matter at hand. In our 1973 MustangConvertible, we still have the original 2.79:1 rear axle gear set. With a 302 2v engine we are not looking to try to transform the vert into a really fast street machine, so the 2.79:1 rear axle gears stay where they are. At 60 MPH we are turning about 1,750 engine RPM in third gear. In the Mach 1 with its original c4 auto tranny, at 60 MPH the engine was turning at about 2,750 RPM in 3rd gear. Not an outrageously high engine RPM to run at, but after 20 minutes on an interstate the RPM would begin to grate on me a bit.

I did not want to change the gears to a steeper ration, as I like the performance with 3.5:! gears in the back end - especially the tractionLok gear set to prevent single tire burnouts. But, I yearned for a more comfortable car to drive on cruises exceeding half an hour of drive time. Other than c haning the rear axle gears I had 3 options:
Live with the 2,750 RPM at 60 MPH
Add a GearVendors OverDrive unit
Replace the C4 with an AOD 4 speed OverDrive tranny

While I was mulling our options I found our C4 began to slip badly in a 1-2 upshift at Wide Open Throttle (it used to burn rubber on a WOT 1-2 upshift when we first got the car). So, fate decided our direction,. I opted to replace the C4 with an AOD that had been rebuilt by Monster. I got the enhanced 1-2 firmer upshift option. In short, the was a success. Now we are able to cruise at 60 MPH and the engine is turning just under 1,800 RPM in 4th OverDrive gear. Plus we retained the same great low end performance in gears 1 though 3 as we had with the original C4.

I video recorded the entire AOD swap, and have a parts list with vendor info, in the two attached files. In one of the videos identified in the respective attached file I show how to splice the C4 Neutral Safety/BackupLight (NSS/BUL) switch into the AOD NSS/BUL harness. I also have several videos showing how to adjust the Throttle Pressure (TP) cable, a critical step to prevent burning the tranny up due to inadequate TP pressure. We set our TP to 38 PSI, higher than the factory 30-35 PSI, in order to increase the road speed when the 1-2, 2-3, and 3-AOD upshifts occur. The upshifrts are also firmer with the TP setting being higher than factory spec.

I defnitely enjoy the Mach 1 a lot more with the AOD.

 

[Hemikiller]

https://www.strangeengineering.net/product/us-strange-gear-ford-9-3-50.html/
https://www.summitracing.com/parts/rmg-f9350/make/ford/model/mustang/year/1973
Looks like I found exactly what I needed, but feel free to check my work!

Be very careful in the ring and pinion you select. Certain brands are known to be noisy, which gets annoying pretty quickly. I spoke to Alan at 8an8incfordrears about rebuilding the rear in my 71 Cougar, and he seems to have the situation down. He told me has had only a handful of noise complaints in many years.

 

[1973 Mach-1]

Agreed with Hemikiller.
I got a Ford old stock 3.0 gearset, when I changed out my old 2.75, and I also put in a Traclok. Many aftermarket gearsets can make noise. My 3.0 gearset was lightly used, and as a consequence, didn't need a break-in period. I used Arizona Differential for the work. They did a GREAT job!

 

[PeteG41]

Agreed with Hemikiller.
I got a Ford old stock 3.0 gearset, when I changed out my old 2.75, and I also put in a Traclok. Many aftermarket gearsets can make noise. My 3.0 gearset was lightly used, and as a consequence, didn't need a break-in period. I used Arizona Differential for the work. They did a GREAT job!

Yeah the used ones I originally asked about were in a 67 mustang. Drove it a little while and decided to go with a different ratio for his driving habits. He said the heat cycles and break in were done at Chucks Speed Center in Phoenix. Just didn't know if it was a good idea to go with slightly used ones, or just wait and get new. I currently have the stock 2.75

 

[PeteG41]

The prior owner of our 73 Mach 1 changed out the original 2.79:1 rear axle gears for a 3.5:1 TractionLok set of gears. The result was him getting some very snappy low end performance with the street/strip 351W (not C) he replaced the original 302 engine with. Frankly, for a vehicle that will be driven on the street, the lowest gear ration I would suggest is 3.5:1. And, if you plan to do any zipping around and Wide Open Throttle launches, I would go the added step and get a TractionLok rear axle gear set, otherwise you will end up frying either one rear tire or the other upon heavy burnout on spirited launches with a 3.5:1 rear axle ratio.

Now for the practical side of the matter at hand. In our 1973 MustangConvertible, we still have the original 2.79:1 rear axle gear set. With a 302 2v engine we are not looking to try to transform the vert into a really fast street machine, so the 2.79:1 rear axle gears stay where they are. At 60 MPH we are turning about 1,750 engine RPM in third gear. In the Mach 1 with its original c4 auto tranny, at 60 MPH the engine was turning at about 2,750 RPM in 3rd gear. Not an outrageously high engine RPM to run at, but after 20 minutes on an interstate the RPM would begin to grate on me a bit.

I did not want to change the gears to a steeper ration, as I like the performance with 3.5:! gears in the back end - especially the tractionLok gear set to prevent single tire burnouts. But, I yearned for a more comfortable car to drive on cruises exceeding half an hour of drive time. Other than c haning the rear axle gears I had 3 options:
Live with the 2,750 RPM at 60 MPH
Add a GearVendors OverDrive unit
Replace the C4 with an AOD 4 speed OverDrive tranny

While I was mulling our options I found our C4 began to slip badly in a 1-2 upshift at Wide Open Throttle (it used to burn rubber on a WOT 1-2 upshift when we first got the car). So, fate decided our direction,. I opted to replace the C4 with an AOD that had been rebuilt by Monster. I got the enhanced 1-2 firmer upshift option. In short, the was a success. Now we are able to cruise at 60 MPH and the engine is turning just under 1,800 RPM in 4th OverDrive gear. Plus we retained the same great low end performance in gears 1 though 3 as we had with the original C4.

I video recorded the entire AOD swap, and have a parts list with vendor info, in the two attached files. In one of the videos identified in the respective attached file I show how to splice the C4 Neutral Safety/BackupLight (NSS/BUL) switch into the AOD NSS/BUL harness. I also have several videos showing how to adjust the Throttle Pressure (TP) cable, a critical step to prevent burning the tranny up due to inadequate TP pressure. We set our TP to 38 PSI, higher than the factory 30-35 PSI, in order to increase the road speed when the 1-2, 2-3, and 3-AOD upshifts occur. The upshifrts are also firmer with the TP setting being higher than factory spec.

I defnitely enjoy the Mach 1 a lot more with the AOD.

The ole one tire fires! I guess the main thing I need to figure out is if I want and do all that at once, or stick with the 2.75 post motor/tranny rebuild until I have the funds to do so. Probably makes more sense to stay with the 2.75 until I can just get the TractionLok 3.5. That way I'm not eating the labor cost twice? Or if anyone has a link to the parts they themselves have used, it would be greatly appreciated. I'm a little over my skis. These are what I have pieced together so far, although I dont know if I need the large or small bearing kit. The only review for the bearing kit stated that if you also do the TractionLok, the supplied bolts dont work.

https://www.cjponyparts.com/ring-and-pinion-mounting-kit-small-bearing-9/p/RPM3K/
https://www.cjponyparts.com/ford-pe...yV8dq7de6YwzW7YglqrwezByV8MxmjhYaAsj_EALw_wcB
https://www.cjponyparts.com/ring-and-pinion-gear-set-9/p/RP24-V/

 

[Bentworker]

I'd run those used gears. The polished spots on the ring gear show that it was initially set up reasonably well. A ford 9" is probably the easiest rear end to set up, and it is a fun project if you have some patience, skill and tools.

 

[PeteG41]

I'd run those used gears. The polished spots on the ring gear show that it was initially set up reasonably well. A ford 9" is probably the easiest rear end to set up, and it is a fun project if you have some patience, skill and tools.

These are a few more pictures. Granted I’m not super knowledgeable but they don’t really look used at all. 1k miles and swapped out.

 

[midlife]

The ole one tire fires! I guess the main thing I need to figure out is if I want and do all that at once, or stick with the 2.75 post motor/tranny rebuild until I have the funds to do so. Probably makes more sense to stay with the 2.75 until I can just get the TractionLok 3.5. That way I'm not eating the labor cost twice? Or if anyone has a link to the parts they themselves have used, it would be greatly appreciated. I'm a little over my skis. These are what I have pieced together so far, although I dont know if I need the large or small bearing kit. The only review for the bearing kit stated that if you also do the TractionLok, the supplied bolts dont work.

https://www.cjponyparts.com/ring-and-pinion-mounting-kit-small-bearing-9/p/RPM3K/
https://www.cjponyparts.com/ford-pe...yV8dq7de6YwzW7YglqrwezByV8MxmjhYaAsj_EALw_wcB
https://www.cjponyparts.com/ring-and-pinion-gear-set-9/p/RP24-V/

For Gawd's Sake, please don't buy rear end parts from CJPonys: they may not have them in stock and will never tell you they are backordered. There's much better places to buy rear end parts than CJ's.

 

[Cleveland Crush]

These are a few more pictures. Granted I’m not super knowledgeable but they don’t really look used at all. 1k miles and swapped out.

Those gears  look to be in excellent + ccondition.

 

[PeteG41]

For Gawd's Sake, please don't buy rear end parts from CJPonys: they may not have them in stock and will never tell you they are backordered. There's much better places to buy rear end parts than CJ's.

Oh I wasnt planning on it, I have had terrible experiences with them. More so I was just making sure that I was on the right track with the parts that I needed to grab, and those were the first ones that popped up.

 

[PeteG41]

Those gears  look to be in excellent + ccondition.

Shooting up there saturday morning to grab them. Easy 45 minutes away, worth the drive.

 

[boilermaster]

PeteG41,
Do you intend to install this gearset yourself ?.
If so please be aware of the fact that a used gearset will not pattern like a NEW gearset, even one with even a couple of hundred miles on it.
Your gear pattern will likely be much broader than what an ideal NEW pattern should look like.
Boilermaster

 

[PeteG41]

PeteG41,
Do you intend to install this gearset yourself ?.
If so please be aware of the fact that a used gearset will not pattern like a NEW gearset, even one with even a couple of hundred miles on it.
Your gear pattern will likely be much broader than what an ideal NEW pattern should look like.
Boilermaster

No I won't be tackling this. These would be well above my paygrade. With a shop that knows what they are doing is a set of used gears an issue? Or is that just if I was doing it myself.

 

[boilermaster]

PeteG41,
A competent shop that does this for a living will know the pattern will be different.
Just wanted you to know beforehand that your pattern will not look textbook even though the end result may be.
Do you intend to drop off your car or just the center section ?
suppose you could ask for pictures, or you could ask if your pattern should be textbook.
Boilermaster