Vintage Mustang Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
I recently acquired a 73 Mustang Converible Q code 351c with an automatic C6 tranny. The torque converter is really acting up and there are most likely other issues. It's stock and not a 3k stall, but acts like it - revs to 3k quickly and then accelarates moderately from there. It's kind of like it has a 3k stall with a governor at 4 or so.

My thought is the tranny is gone and needs replaced. I don't know if I want to go with fully rebuilt standard c6 with a modest shift kit from a company or just have this one rebuilt. If I buy one, I have heard a lot of people going with a 5 speed automatic, but I don't know how easily those drop in or what the advantages to them are.

And if I buy one, where is the best place? Or should I just try to get this one rebuilt. I believe it is the original tranny, but I haven't bothered to check too carefully.

I would rather keep it as close to stock as possible, but if there is an advantage to either the 5 speed or a fully rebuile one, I would love to weigh the options. Either way it's going to cost some decent bucks so I want to make the right choice early on.

Thanks for any suggestions.

Bob

73 Mustang Converitble 351C
68 GTO
 

·
Registered
Joined
·
2,273 Posts
I didn't know you could put a 5-speed automatic behind a 351C. Are you sure you don't mean the 4-speed auto like the AOD?

I'm sold on the overdrive transmissions for cars that get driven more than a little. But if you have the original tranny and want to keep it that way, you could look at a Gear Vendors overdrive unit. They're pricey, but very stout and probably simpler than an AOD swap.

Either way, it sounds like your transmission needs to come out so the torque converter can be changed. That would be the time to rebuild or replace it...

Good luck,
MrFreeze
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
Thanks! I hadn't seen it specifically for the 351C, but just in general, so it may not be possible in my config. I'm not going to use this as a daily driver, so the AOD isn't a huge deal to me but since I'm going to redo the tranny anyway, now is the time. I thought maybe with AOD I would get a lower starting gear and more midrange power.

Any thoughts on buying a fully rebuilt C6 with torque converter or just going to a local shop and rebuiding the existing C6? If replacement, any suggestions as to who rebuilds the best tranny's?
 

·
Registered
Joined
·
537 Posts
If its the original tranny, it is a specific C6 with a high stall conerter from the factory. Your reving up before moving issue could be many things. if it was me and I wanted an original car I would rebuild the one you have including your converter.
If I wanted to drive a lot I would put a 4r70w 4 speed tranny with a Baumann electronic controller or if you like shifting yourself a Manual Valve body kit.
I have the 470w with manual shift in my convertible.
It made a huge difference from the FMX
 

·
I won a special award
Joined
·
7,409 Posts
If its the original tranny, it is a specific C6 with a high stall conerter from the factory. Your reving up before moving issue could be many things.
Ditto. The 351 CobraJet C6 used a 10 inch converter that utilized a special flexplate. I don't know if anyone reproduces that flexplate.
 

·
Registered
Joined
·
5 Posts
Discussion Starter #6
Great feedback. I was unaware that the Q code c6 had a 2500-3k stall converter on it, but after following up on your leads that appears to be the case. Must have to do with the reduced compression and altered HP/Torque curve of the 351c from the 64-70 model years. I know there is a vacuum leak in the intake so there could be something from that as well.

I think I will look at troubleshooting and rebuilding what I have first. If it's a basket case, I'll check into a new one. This is a great forum and I appreciate all the replies. I hope to be able to give as well once I get up to speed on the Mustang specifics.
 

·
Registered
Joined
·
9,844 Posts
Ditto. The 351 CobraJet C6 used a 10 inch converter that utilized a special flexplate. I don't know if anyone reproduces that flexplate.
I had a new converter put into my 73 Q Code C6 with no problems.

Here's what I would do. Send the tranny to Broader Performance and they will do whatever you want. Based on my experience with my Q Code I would put in a low gear kit (10% lower first gear) with about a 2500 stall converter. That will get you car out of the hole with having that mushy feeling. The 4V Cleveland needs gearing and a loose converter to get it into the power band.

It might seem like a hassle to send it to Broader but it is an absolute sure thing. I wish I had done it. I used a local shop and had to take it back twice.

Broader built a C6 for my FE motor and nailed it. Exactly the shift quality I wanted.
 
1 - 7 of 7 Posts
Top