Convert Auto to Manual

[Jack_Straw]

Recently became the owner of a numbers matching early production 71' 351-4V Mach 1.

I want to convert my auto 3 speed to a 4 or 5 speed. While I don't necessarily want to remove any original parts, the current transmission has some problems and I did want a stick to begin with.

Anyone have any suggestions for what route I should take? I know for certain I'm going with Tremec but not sure which option would be best (T-5, T-56, TKO, TKX).

Would appreciate any feedback from anyone that's gone through the process or any general knowledge about each of these transmissions.

 

[giantpune]

Over the summer, I did the C6 to TKX swap.
I have another car with a T5 and a cable clutch. It feels very much like driving a late 80s foxbody mustang. When I was doing the one this summer, I wanted a little nicer.

So far, I am happy with my decision. I like the TKX more than the T5 and I like the hydraulic clutch more than the cable.

TKO is essentially dead. It is replaced by the TKX.
T-56 is physically too big to fit without cutting our transmission tunnel.

Whichever transmission you pick, you can install the tremec calculator app. It lets you plug in your rear end ratio and tire size. And it knows the gear rations for all the tremec transmissions. It will show you RPM and vehicle speed at various RPM. That way you can pick the one that fits the rest of your car. You dont want one with too little gear so when you shift from 4th to 5th on the highway, the RPMs are so low it falls on its face. Or its geared so low you have to slip the clutch a lot to get started from a stop and 1st gear takes you up to 35mph at 3000rpm. Add you (probably) dont want one on the other end of the spectrum where you have to shift through 3rd gear to make it over 40mph and 5th gear is running 4000rpm at 70mph.

Pick somewhere in between those extremes.

https://7173mustangs.com/threads/the-snot-rocket-green-73-fastback.43098/post-438723

 

[tony-muscle]

I also went from C6 to manual. In my case it was a TKO600 because the TKX was not out, but nowadays a would choose the TKX. A tad smaller and better shifting.
The process is relatively simple. I went with Modern Driveline and bought everything from them. The cable, pedal, clutch/plate and transmission. I bought the bellhousing elsewhere because it was cheaper. Depending the pressure plate you will need a new starter. The pedal clutch goes right on the pedal bracket with the provided bearings. If I were to do it again I think I would go with the hydraulic setup instead of cable. I had an issue with the bracket that holds the cable to the firewall but they have since reinforced it.

 

[71coop]

I tend to agree with Giantpune. I ran a TKO in my 79 vette with a 427 SBC and modified suspension and loved it - it was perfect for that. I hear the TKO is a great upgrade. A friend just put a TKX in his 66 Comet, and really likes it. If I were looking at going manual, that would be the first option I would explore.

 

[InjectedMach]

Recently became the owner of a numbers matching early production 71' 351-4V Mach 1.

I want to convert my auto 3 speed to a 4 or 5 speed. While I don't necessarily want to remove any original parts, the current transmission has some problems and I did want a stick to begin with.

Anyone have any suggestions for what route I should take? I know for certain I'm going with Tremec but not sure which option would be best (T-5, T-56, TKO, TKX).

Would appreciate any feedback from anyone that's gone through the process or any general knowledge about each of these transmissions.

Call Modern Driveline and find out which trans best fits your needs. If they say a t56 will fit that would be my personal choice because of the hydraulic throw out bearing, how they shift and multiple shifter locations etc. The folks at modern driveline sell complete conversion kits too which is very convenient so all your parts and tech support come from 1 place. My$.02

 

[giantpune]

Call Modern Driveline and find out which trans best fits your needs. If they say a t56 will fit that would be my personal choice because of the hydraulic throw out bearing, how they shift and multiple shifter locations etc. The folks at modern driveline sell complete conversion kits too which is very convenient so all your parts and tech support come from 1 place. My$.02

The hydraulic throwout bearing is a completely separate part from the transmission. You can use that style of throwout bearing on a T5 or a TKX if you want. And you can run a T56 with an external slave cylinder or even a cable clutch.

 

[rcadd1ct]

I gave a malwood pedal and McLeod hydraulic T/O bearing with my top loader.

I want the 6spd, but will most likely go with a 5 due to size.

I wish I had cut my tunnel before I lizard skinned the car.

 

[TheDude]

I'm using a stock pedal assembly I found on Ebay pretty cheap with the Hydramax hydraulic TO bearing and a T56 Magnum 6 speed. On my car there was no cutting anywhere. The T56 uses the stock shifter hole in the tunnel and nothing needed to be clearanced underneath. If I need to open this up again, I may switch to an external slave for the bearing for serviceability as I don't love having to drop the trans to service the slave. And agreed with reaching out to Modern Driveline. They'll give you a good idea of the full project pretty quickly. Also keep in mind there's a good chance you'll need a new driveshaft.

 

[tony-muscle]

I'm using a stock pedal assembly I found on Ebay pretty cheap with the Hydramax hydraulic TO bearing and a T56 Magnum 6 speed. On my car there was no cutting anywhere. The T56 uses the stock shifter hole in the tunnel and nothing needed to be clearanced underneath. If I need to open this up again, I may switch to an external slave for the bearing for serviceability as I don't love having to drop the trans to service the slave. And agreed with reaching out to Modern Driveline. They'll give you a good idea of the full project pretty quickly. Also keep in mind there's a good chance you'll need a new driveshaft.

Wow, I always thought you needed to partially cut the tunnel to fit the Magnum. Any issues with headers? How do you like driving a 6 speed? I sometimes wish I had a shorter ratio on 5th gear. Now in 5th gear the car has a hard time gaining speed. With 6 speeds I could have shorter ratio in 5th for the track and use 6th on the highway.

 

[TheDude]

At least on my car there was no cutting or clearance issues with the header or anything else other than having to switch to a smaller starter. For some background, I got the car with no trans (the auto was removed) and a new T56 Magnum in a box on the back seat and I been building it a chunk at a time ever since.

The biggest issue I've had is that I've been doing this a piece at a time and up until recently my gearing was way off. This thing initially had a 2.79 gear in the back and that T56 is geared so tall it was very tough to just drive around down and had little torque. On paper, that trans with that rear and the 20" wheels with tall tires I was running, it had the top speed in 6th at over 300MPH and 1st gear would top out at over 70 I think . While that's comical and sucked around town, the thing was an absolute freeway cruiser like that. I'd cruise at 65 at like 1300RPM. So no torque but I was probably getting Prius level MPG on the freeway.

Finally switched out to a 4.10 rear end and 18" wheels and it's way more drivable. On this trans both 5th and 6th are overdrive gears and it'll happily cruise on the freeway in either. So now it's a nice combo of low end torque and drivability and still very happy to cruise on the freeway. I have to admit that cruising on the freeway matters more to me than I thought it would. It is very nice to be able to eat up miles with the car not working very hard or making too much noise.

 

[giantpune]

I'm using a stock pedal assembly I found on Ebay pretty cheap with the Hydramax hydraulic TO bearing and a T56 Magnum 6 speed. On my car there was no cutting anywhere. The T56 uses the stock shifter hole in the tunnel and nothing needed to be clearanced underneath. If I need to open this up again, I may switch to an external slave for the bearing for serviceability as I don't love having to drop the trans to service the slave. And agreed with reaching out to Modern Driveline. They'll give you a good idea of the full project pretty quickly. Also keep in mind there's a good chance you'll need a new driveshaft.

Well damn. I did reach out to modern driveline and they were the ones that told me a T56 would need the transmission tunnel widened. Thats the only reason I went with the TKX instead.

I get the impression they have more experience with the earlier model mustangs than with ours.

 

[Randyi00]

I've been thinking about doing the auto to manual swap for many years already, hoping to pull the trigger in the next year or two. I'm curious to hear from people who have done the swap from a C6 what the performance difference feels like. I know the C6 is a power sucking pig and so I'm curious if going to a good modern manual offers a real difference in performance either by feel or by the clock.

 

[tony-muscle]

Well damn. I did reach out to modern driveline and they were the ones that told me a T56 would need the transmission tunnel widened. Thats the only reason I went with the TKX instead.

I get the impression they have more experience with the earlier model mustangs than with ours.

I agree. That's the impression I had back then when i went with the TKO

 

[TheDude]

I was told the same thing actually from Modern Driveline and others. Went at it the first time to just fit it up there and see where we need to start cutting and everything just worked. No clearance issues anywhere, plenty of room all around it and the shifter was located perfectly.

Not sure if my car is somehow weird, but everything I read and everyone I talked to before installing this said that I'd need cut but thankfully I didn't have to. So I'm assuming it's like you guys said and most of the experience is with older cars and not that mine is just some kind of oddball with a phat tunnel.

 

[tony-muscle]

I was told the same thing actually from Modern Driveline and others. Went at it the first time to just fit it up there and see where we need to start cutting and everything just worked. No clearance issues anywhere, plenty of room all around it and the shifter was located perfectly.

Not sure if my car is somehow weird, but everything I read and everyone I talked to before installing this said that I'd need cut but thankfully I didn't have to. So I'm assuming it's like you guys said and most of the experience is with older cars and not that mine is just some kind of oddball with a phat tunnel.

This is very interesting. Maybe there are differences in the tunnel or it may also depend on the motor mounts. If the mounts are lower it will move the whole drive train lower and allow for more clearance. I know there are differences in the motor mounts between 71 and 72 but I have not paid attention if they are lower or higher. I also know there was another user in here that back then told me that he needed to cut a little to fit the TKO, but I didn't need. Go figure. However, I had to increase the drive train angle a little to fit the transmission. Did your drivetrain angle change or you were able to keep it stock?

 

[TheDude]

Yeah it is weird and even though it worked on mine I'm hesitant to tell someone to go for it, it fits. Drivetrain angle stayed stock. Not sure if this changes things at all, but this car came with a 302 originally and was swapped to 351C (1969 block) in the mid 80's I think. All the mounts and everything look stock.

 

[rcadd1ct]

American power train and modern driveline both told me I would have to trim the tunnel.

Maybe they are confusing our cars with the earlier models.

I definitely would like the double overdrive. I have enough torque to cruise in 6th.

 

[giantpune]

Sounds like you need to be the guinea pig. Take one for the team.

 

[rcadd1ct]

Sounds like you need to be the guinea pig. Take one for the team.

Me?

I might if I find another job.

tech guy looking for work for a while now.

 

[InjectedMach]

The hydraulic throwout bearing is a completely separate part from the transmission. You can use that style of throwout bearing on a T5 or a TKX if you want. And you can run a T56 with an external slave cylinder or even a cable clutch.

Yes it is a separate component but cables flex and forks create exhaust interferences, the internal slave is clean, and I've done about 4 t56s into 67 68 cars with no floor mods at all.