Considering C6 to AOD

[RC92234]

Mileage is 137k. My C6 slips in all gears, doesn't upshift under heavy throttle and RPMs at 60mph are over 3000rpm (3.25 rear). I'm not a racer -- the car is just for enjoyable top down cruising. Plain rebuilds, no shift kit enhancements, etc, run $2200-$3000 here. Does not include unforeseen repairs. Would not lower highway speed rpm.

I know the benefit of AOD conversions include lower highway speed rpm and for C6s, a considerable saving in weight. I don't think I have seen Trans Depot discussed. Standard rebuilt AODs run $2400 or so, although they list on eBay for $1700. I'd expect shipping, labor and the necessary conversion details the low price unit installed would run to about the middle of the rebuild cost.

This may be one of those times where there's a significant benefit to not keeping things as original as possible.

https://www.ebay.com/itm/3504830218...0Vqv25mWHdE+bTaZ1TBK6MDg==|tkp:Bk9SR-jvypHpYQ

 

[Sheriff41]

I did this conversion about 20 years ago and have not had any problems with the AOD. I've been pretty satisfied with it but will be changing to a 5-speed manual setup this summer.

There is more to the swap than meets the eye. You'll need to modify your shifter, cooler lines, adapt the TV (throttle valve) cable, and driveshaft, among other bits and pieces. Things like these can drive up the cost of the swap.

Do your research, check out @mrgmhale thread and his YouTube videos for some in-depth information. Also look into the 4R70W transmission. It's a more modern AOD with electronic control.

 

[rackerm]

I did this conversion about 20 years ago and have not had any problems with the AOD. I've been pretty satisfied with it but will be changing to a 5-speed manual setup this summer.

There is more to the swap than meets the eye. You'll need to modify your shifter, cooler lines, adapt the TV (throttle valve) cable, and driveshaft, among other bits and pieces. Things like these can drive up the cost of the swap.

Do your research, check out @mrgmhale thread and his YouTube videos for some in-depth information. Also look into the 4R70W transmission. It's a more modern AOD with electronic control.

Aside from the obvious overdrive gear for cruising advantage over a C6, there is also a power advantage. C6 trans are very strong, but that comes at a cost in weight and HP drain by about 30% more than a C4, not sure what the percentage is for an AOD, but my guess is, it is close to the same HP drain.

So between, having an extra OD gear (vs C6 3 gears), less weight, and less HP drain, I think the answer is obvious to me.

 

[Steve McMahan]

This was an interesting Motor Trend article on power loss:

https://www.motortrend.com/how-to/ccrp-0311-drivetrain-power-loss/

 

[Hemikiller]

The AOD is a nice transmission and works well. It's Achilles Heel is the TV cable. It has to be set correctly or it'll burn up pretty quickly. Our 71 XR7 has an AOD behind the 351C with 3.50 gears. It's real nice on the highway as the motor is just loafing along. I do need to get a pressure gauge on the transmission to get the TV adjustment set perfectly.

The current trend is to procure a 4R70W from a V6 Mustang and use a Baumann controller. You can probably get a used unit for couple hundred at a local pick-your-part and swap it in without issue. The transmissions are reportedly good for 500hp and just last and last.

Some good reading on this thread if you decide to go this way:

https://www.vintage-mustang.com/thr...uide-into-a-1965-mustang-convertible.1203917/

 

[jackf]

I did this and am very happy. I'm running 389 gears and highway cruising is much more pleasant. One caveat, I found the warranty to be useless. It costs more to ship the tranny back and forth than to have local shop repair. Just something I wish someone had told me. PS. I did need to change driveshaft, flexplate, crossmembet, etc, but it's all doable and not crazy money.

 

[Hotstang]

I did the swap from C6 to AOD and dropped the rear end to 370. I went with a lock up converter to lower the highway RPMs even more. I like the lower 1st gear and cruise. I don’t like the lockup stays engaged on coasting to a stop and causes the car to buck with the large cam. I either have to manually down shift or shift into neutral when coming to a stop. The fix is a non lockup converter which will increase the cruise RPM.
if I has to do it over I would swap in a 4r70w with electronic controller. Same size as the AOD but stronger to start with. Controller allows you to shift up and down as you choose.

 

[Fabrice]

I agree with @Hotstang on the 370 rear end. I have a 350 and did the AOD swap last year. I find the combo not being as I wanted it (drove 2 tbird 5.0 with same trans and was expecting similar, but its not). With my 18' tires this creates often situations where i'm near of idle rpms, great for fuel economy but far less for the fun as you often do not want always to shift down, just give gas. Having a 370 would be now my better choice. I did the restoration of the AOD myself, and the flaws this trans has are easy fixes to get it as strong as a C6. Sonax for instance offers a ring that requires a minimal machine (a groove for it) on the end of the shaft to prevent the inner shaft to go bang drum and a double lock ring for the forward gear right behind the pump, that was potentially opening itself under heavy load thx to centrifugal forces, releasing the entire assembly. I think I would now go for a non locked converter vs the 2500 stall locked that I have. For that one you need replace the innershaft by a performance version and had an extra oil cooler.
I read that you need to replace the driveshaft. That is only if you go find an AOD with a long governor. There were 3 models, all same bodies, but different governor length. The ones coming from mustangs, t-birds have the short one, with that model, you only need to buy a new short yoke. Sonax has a very nice one with the same u-bolts size as the original and its affordable too. As a side note, know that this yoke has very tight tolerances and installing new u-bolt is not a walk in the park as with the original.

I too will probably go for a manual trans next time, but overall, going for AOD was no bad choice.

I have also rebuild my 429 C6, and aside adding the rare 5 planetary that came with the 429 cars, even if your trans is not having the best setup, its easy to beef it up. adding extra friction plates for instance can be done with minimal machining (basically reducing the pressure plates thickness). They are not ideal on highway speeds, but dang it, they are fun!

 

[Alexei]

I also did the swap and I fully agree with the colleagues. I also installed a Holley Sniper, last year, and that matched perfectly to the AOD. Now it’s start and go!

 

[Sheriff41]

I did this conversion about 20 years ago and have not had any problems with the AOD. I've been pretty satisfied with it but will be changing to a 5-speed manual setup this summer.

There is more to the swap than meets the eye. You'll need to modify your shifter, cooler lines, adapt the TV (throttle valve) cable, and driveshaft, among other bits and pieces. Things like these can drive up the cost of the swap.

Do your research, check out @mrgmhale thread and his YouTube videos for some in-depth information. Also look into the 4R70W transmission. It's a more modern AOD with electronic control.

I didn't mention it but I run 3.89:1 gears with my AOD. I'd recommend 3.70 for an all around street gear.

 

[mrgmhale]

Our 73 Mach 1 originally had a 302 and C4 in it. Prior owner dropped in a street/strip built 351W (not C), and replaced the 2.79:1 rear axle gears to 3.50:1 TractionLok rear axle gears. The C-4 was slipping so I dropped in an AOD, and am very pleased with the results, But, were I to do it again I would opt for a 4R70W and 3rd party controller - just like HemiKiller & others suggest. I was able to adjust the Throttle Valve at the carburetor, and readjusted it a few times as I increased the pressure a little above factory specs to get a higher road speed before the 1-2 and 2-3 upshifts occurred. It was not hard to do, but connecting the oil pressure gauge, and removing it afterward, was a PITA. That said, I would not hesitate to get an AOD again.

HemiKiller suggests adding an oil pressure gauge to monitor the AOD Throttle Valve pressure. I had not even considered doing this (I run mine at 39 PSI to increase the road speed for 1-2 and 2-3 upshifts, and a firmer upshift). But, because a Throttle Valve setting being too low (under 30 PSI with the adjustment gauge in place), which can lead to transmission damage, I am think I better do that to help avoid problems.

Following are some links to my Google Drive where you can find some PDF files. One PDF has the different vendors and parts we used for our AOD swap. The other has a list of YouTube links, and a brief description of the videos we shot of the entire swap and Throttle Valve pressure adjustment.

https://drive.google.com/file/d/1mHbDzTpWLobsFDc8PsL83oe6hqaPVags/view?usp=share_link

https://drive.google.com/file/d/1zxHhpcYvA3FsP1Q7idzvUEQB_a05q3b9/view?usp=share_link

I AM NOW ABLE TO CRUISE AT 60 MPH IN 4TH (OVERDRIVE) GEAR AND THE ENGINE RPM IS JUST UNDER 1,800, WHEREAS WITH THE C4 IN 3RD GREAR IT WAS CLOSER TO 2,800 RPM. Sorry about the SHOUTING, the CapsLock get got pressed, Ooops...

 

[RC92234]

Our 73 Mach 1 originally had a 302 and C4 in it. Prior owner dropped in a street/strip built 351W (not C), and replaced the 2.79:1 rear axle gears to 3.5:1 TractionLok rear axle gearsl The C-4 was slipping so I dropped in an AOD, and am very pleased with the results, But, were I to do it again I would opt for a 4R70W and 3rd party controller - just like HemiKiller suggests. I was able to adjust the Throttle Valve at the carburetor, and readjusted it a few times as I increased the pressure a little above factory specs to get a higher road speed before the 1-2 and 2-3 upshifts occurred. It was not hard to do, but connecting the oil pressure gauge, and removing it afterward, was a PITA. That said, I would not hesitate to get an AOD again.

Following are some links to my Google Drive where you can find some PDF files. One PDF has the different vendors and parts we used for our AOD swap. The other has a list of YouTube links, and a brief description of the videos we shot of the entire swap and Throttle Valve pressure adjustment.

https://drive.google.com/file/d/1mHbDzTpWLobsFDc8PsL83oe6hqaPVags/view?usp=share_link

https://drive.google.com/file/d/1zxHhpcYvA3FsP1Q7idzvUEQB_a05q3b9/view?usp=share_link

I AM NOW ABLE TO CRUISE AT 60 MPH IN 4TH (OVERDRIVE) GEAR AND THE ENGINE RPM IS JUST UNDER 1,800, WHEREAS WITH THE C4 IN 3RD GREAR IT WAS CLOSER TO 2,800 RPM. Sorry about the SHOUTING, the CapsLock get got pressed, Ooops...

Many thanks!

 

[mrgmhale]

I did the swap from C6 to AOD and dropped the rear end to 370. I went with a lock up converter to lower the highway RPMs even more. I like the lower 1st gear and cruise. I don’t like the lockup stays engaged on coasting to a stop and causes the car to buck with the large cam. I either have to manually down shift or shift into neutral when coming to a stop. The fix is a non lockup converter which will increase the cruise RPM.
if I has to do it over I would swap in a 4r70w with electronic controller. Same size as the AOD but stronger to start with. Controller allows you to shift up and down as you choose.

I agree with no lock-up torque converter. And although I am very pleased with how our AOD swap, replacing a C4, I also agree re: using a 4R70W with external electronic control module were I to do this again. It is not worth replacing the AOD with a 4R70W as long as the AOD performs well (it does), but being able to adjust the tranny electronically vs manually adjusting the Throttle Valve pressure setting, and shift points, is attractive - especially now that I have done that manually on the AOD a few times.