2.75 to 3.50 3rd member swop issues

[71ProjectJunk]

The adjusting screws will be marked left and right, they will at least have an L and an R on them. Easy to screw this up. Another thing is did you put a new self adjuster kit when you did the brakes? A lot of people will just buy new shoes, some will also buy a new spring kit, and fewer will buy the self adjuster kit when doing rear drum brakes. To do this job right you really need to change the shoes, the spring kit, and the self adjuster kit. The spring kit and the self adjuster kit are pretty cheap, and IMHO are a must to change when you do a rear brake job. The backing plate raised flat areas can also be an issue, I just did my rear brakes and the lower raised flat areas next to the adjusting screws were really worn, I had to put a bunch of weld on them and them grind them flat again. And before you start the brake job you need to put a bit of brake grease on all the raised areas of the backing plates so the shoes can move freely, you should also put some brake grease on the threads of the adjusting screws, and if you reuse old adjusting screws they need to be cleaned thoroughly and greased well, to make sure that they move freely. Even when all the used stuff looks good, and sometimes it can be reused, the self adjusting cables will stretch with time and if they are stretched, they will not adjust your brake properly, and it is very hard to notice when they are stretched. Here is one of the best Ford rear drum brake videos:

 

[timachone]

As 71ProjectJunk said, I did exactly this, +1

 

[Superbond]

I bought the brakes and spring kit from Napa. Funny thing is you can buy most parts for your car from them and they look like quality parts.
When taking the brakes apart. I left the adjusters by their original side of the car. You can only install them one way. So I don’t know what to think

 

[Superbond]

Oh and the backing plates looked good from what I remember

 

[Superbond]

i cleaned and put anti-seize to the threads after I cleaned them. I didn’t notice any backing plate issues but wasn’t looking for those issues just for rust

 

[will e]

After installing the 3.5 gear in my Mustang and driving it for a few years I decided the RPM's were too high at 65mph (just over 3000 RPM). I installed a gearvendors overdrive

https://www.gearvendors.com/product/automatic-3-speed-fmx-3/
It's not a 'cheap' solution but is comparable to swapping in an AOD. At 65mph my RPM's are now around 2400. Even at 45 the difference is noticeable and pleasant.

 

[Superbond]

What’s a gearvendors overdrive?

 

[Superbond]

I’m looking to put in an Aod soon

 

[will e]

What’s a gearvendors overdrive?

I added a link in my previous reply. They are an independent company that creates an 'overdrive' unit that is attached to the transmission. The unit itself is pretty standard and they have dozens of different adapters for various transmissions. The stock tailshaft is removed and the adapter and overdrive unit are attached. The drive shaft will need to be shortened. There is some electronics involved but it's pretty easy stuff.

The overdrive unit is self contained and does not require any connections for oil or cooling.

It's a planetary gear system with a clutch plate. The spinning of the unit creates the pressure and a solenoid is used to activate the overdrive. The unit can be activated at pretty much any speed over 25 or so MPH. It provides a 22% overdrive.

The electronics can activate it for you or you can use a switch. It deactivates itself whenever the speed of the car gets down to about 22mph.

There are many advantages and disadvantages to this compared to an AOD swap.

I think it's easier to install. I did mine on my garage floor. It uses the factory transmission mount location.
I kept my already built C6. The shifter continues to work as normal.
Used with a C4/C6 the first gears is a bit steeper than an AOD (faster holeshot) but the FMX first gear is very similar to the AOD
The AOD does have a greater overdrive so it will slow down the RPM's a bit more, this might provide the difference between say 3.5 and 3.73 gears for the same RPM cruising range.
The gearvendors can be engaged at any speed above 25mph or so regardless of what gear the transmission is in. This allows 'gear spitting'. You basically end up with 6 forward gears but in practice I don't split gears every time. (Kinda like folks with 6 speed manuals don't always go through all of the gears).
I like to split 2nd to 3rd sometimes if I an getting on it. I also like the passing gear I get when going from 3rd to 2nd with the overdrive engauged.

For me it made sense. I had a built c6. I didn't want to mess around with flexplates, shift linkages, possible exhaust interference and such. If I had an FMX I might have gone the AOD route just because FMX has less support than the c4/c6.

Price wise it was kind of a push. 10 years ago or so when I installed the gearvendors the cost to convert to AOD vs GV was pretty close depending on how you did the math and if you wanted to do the labor yourself.

 

[mrgmhale]

I’m looking to put in an Aod soon

we transplanted an AOD into our 73 Mach 1, with its 3.5:1 TractionLok rear axle gear set and street/strip built 351 W (not C). Worked out great. See attached for our parts and vendors list. In one of the files is a list of you Tube videos of the entire project, to include splicing the AOD Neutral Safety/Backup Light Switch into the NSS/BUL Switch harness from the original 302

 

[mrgmhale]

After installing the 3.5 gear in my Mustang and driving it for a few years I decided the RPM's were too high at 65mph (just over 3000 RPM). I installed a gearvendors overdrive

https://www.gearvendors.com/product/automatic-3-speed-fmx-3/
It's not a 'cheap' solution but is comparable to swapping in an AOD. At 65mph my RPM's are now around 2400. Even at 45 the difference is noticeable and pleasant.

In our case the C4 in our 73 Mach 1 was beginning to slip badly in its 1-2 upshift at WOT. So, I would have had to rebuild it and get the GearVendor solutions. In my case it was going to be less costly to get a rebuilt AOD and transplant it vs rebuilding the C4, then adding the GearVendor unit. So, it came down to spending about the same money whether I rebuilt the C4 and added GearVendor or just swapping the AOD for the C4. I decided to do the AOD simply because I felt the C4 would not be able to handle the 360 HP (at the crankshaft) of the 351W (not C) street/strip built engine as well as the stronger AOD tranny. I could have gone either way, but I opted for the tranny that is more capable of handling relatively high output, plus gave the advantages of an OverDrive unit. I am certain that had I gone the GearVendors direction I would have been equally pleased with the result.

 

[will e]

In our case the C4 in our 73 Mach 1 was beginning to slip badly in its 1-2 upshift at WOT. So, I wuld have had to rebuild it and get the GearVendor solutions. In my case it was going to be less costly to get a rebuilt AOD and transplant t vs rebuilding the C4, then adding the GearVendor unit. So, it came down to spending about the same money whether I rebuilt the C4 and added GearVendor or just swapping the AOD for the C4. I decided to do the AOD simply because I felt the C4 would not be able to handle the 360 HP (at the crankshaft) of the 351W (not C) street/strip built engine as well as the stronger AOD tranny. I could have gone either way, but I opted for the tranny that is more capable of handling high output, plus gave the advantages of an OverDrive unit. I am certain that had I gone the GearVendors direction I would have been equally pleased with the result.

Right on! Yeah, if my transmission was on its last leg or not able to handle the power I would have opted for the AOD as well. Just between you and me, if the C6 ever gives up the ghost I might toss in an AOD and put the gearvendors behind it. I could put in some very steep gears and still a great cruise RPM too.

 

[Superbond]

I looked at your information on the od add on.
It’s not for me as my FMX transmission has a leak coming from where a coolant line screws into the transmission. I had a welder fix it but it’s leaking again. So getting a used AOD from a 88-92 and get it rebuilt sounds better for me.

 

[will e]

I looked at your information on the od add on.
It’s not for me as my FMX transmission has a leak coming from where a coolant line screws into the transmission. I had a welder fix it but it’s leaking again. So getting a used AOD from a 88-92 and get it rebuilt sounds better for me.

That's a good plan.

 

[Superbond]

oh brother!
Here we go!!!
So
After I did the 3rd member swop( 2.75 to 3.50) I have had a back brake issue. First I could smell brakes after short ride. I adjusted the new brakes. Spun the wheels and tires spun freely. Nice!
Went for another rid. No more smell of brakes. But after the ride I checked the temp of the back and front brakes. Front were under 100 degrees but the back brakes were both around 245 degrees. You could smell what seem to smell like if there was plastic stuck to something hot. I had new bearings and seals for the 28 spline axles.
I’m worried that I’m getting gear oil passing past the seals and into the brake drums!
Don’t have time right now to pull the wheels off and look into the drums.
Is there a way without pulling it apart to put inspect the back brake issue

 

[Stanglover]

Back brakes was and still is one of those jobs I don't like to tackle. A couple of years back now, I had my axle rebuilt and a Track-Loc installed, but keeping the 3.25:1 gears. At the same time, I redid the back brakes, but before I pulled them apart, I took some pics and glad I did. Where I screwed up was the parking brake springs that I got on wrong. I had posted about the axle rebuild that ended up with a "Stinky Rear End" (thread name) with pics of a small leak on one side. Someone noticed the incorrect spring and mentioned it to me. The springs got reinstalled.
The "stinky rear end" was caused by the Ford friction modifier that is a MUST to be added with a Track-Loc. Boy does that stuff STINK!!! After a while it and the small leak went away.
What I'm saying here is I would go back and double check all the components are correctly installed. Pull it all apart again if in doubt and redo it. One thing out of place could be the cause. Something ain't right there. The brakes should be no hotter than the axle housing.

EDIT: adding link to Stinky Rear End, it may be useful........ or not. Start around post #17
https://7173mustangs.com/threads/stinky-rear-end.35935/

 

[Mister 4x4]

Could your e-brake cable possibly be a little too tight? If you had fluid coming out of the axle seals, the whole thing would be 'wet,' but it sounds like it's all dry at the brakes... just hot. You should have a few inches travel on the pedal before it really starts engaging the shoes.

Also, have you checked the differential for excessive heat when you noted the high heat on the brakes (the pinion would be the best place to check that)? I'm curious because if it's too hot inside the diff because of increased friction (from not being properly set-up), the heat can travel down the axle and transfer to the drums - since the axle tubes are in the wind and not directly connected except for the bearings, they might not be as hot. The internals of the diff would be super hot if that's the case.

It's a long shot, but I hope that helps.

 

[Stanglover]

Also, have you checked the differential for excessive heat when you noted the high heat on the brakes (the pinion would be the best place to check that)? I'm curious because if it's too hot inside the diff because of increased friction (from not being properly set-up), the heat can travel down the axle and transfer to the drums - since the axle tubes are in the wind and directly connected except for the bearings, they might not be as hot. The internals of the diff would be super hot if that's the case.

It's a long shot, but I hope that helps.

I'll buy that. Sounds very possible.

 

[Superbond]

So
Here we go!
Driving around yesterday and my wife said it smells like burning plastic. When we got home I checked the back brake drums with a temperature tool. It said both brake drums were at 245 degrees. I wish but didn’t think about it at the time to check the temperature of the diff case. When I thought of it the temperature was 110 degrees for both brake drums and the diff.
I’m hoping it is just the new brakes acting up and not the new differential. Could it be the new differential making it head up and if so what would cause that?

 

[DAverkamp]

So
Here we go!
Driving around yesterday and my wife said it smells like burning plastic. When we got home I checked the back brake drums with a temperature tool. It said both brake drums were at 245 degrees. I wish but didn’t think about it at the time to check the temperature of the diff case. When I thought of it the temperature was 110 degrees for both brake drums and the diff.
I’m hoping it is just the new brakes acting up and not the new differential. Could it be the new differential making it head up and if so what would cause that?

You have a few things going on but making sure the diff is breathing through your vent hose is step one and then onto the other items you are trying to eliminate. Put your temp gun in the car on your next run to shoot everything going on.