Ok so I have finally decided to go auto with my '03 TT Cobr a. Just want to get others opinions on which is the better way to go. What are the pros and cons to each. I am looking at a turbo 400 or a 4R70W, need some help thanks!!
Which auto is best?
- Thread starter 03TTMO
- Start date
Turbo 400 doesn't have overdrive for street driving, but can be built pretty stout. It must be adapted to the ford motor.
You can buy a mustang gt with a blown motor for around 1000 if you are patient and do a full auto swap and build the 4r70. But they are more expensive to build and not known for handling a ton of power. They have overdrive though.
How much power you plan on making?
You can buy a mustang gt with a blown motor for around 1000 if you are patient and do a full auto swap and build the 4r70. But they are more expensive to build and not known for handling a ton of power. They have overdrive though.
How much power you plan on making?
As my car sits I make 947, but I am looking into upgrading the turbos in the future so I would like something that can handle 1200hp.
From what I've heard the turbo 400 is a more reliable way to go, I know there is no overdrive. But to build that it's cheaper and if anything happens it's cheaper to rebuild. I've been told there is a gear bender, or something like that that I can basically have overdrive. Heard it's expensive though.
Gear Vendors. It's an incredibly expensive way to knock down RPM by a few hundred. Just run a tall rear tire and low gear and won't be that bad.
If you want OD and a strong trans you can always have a 4L80 built. It's "kind of" like a TH400 with an OD but it's considerably more than a built TH400.
4R's when built well can take a beating but I'm more trusting of the old TH400 and that's what is in my turbo 03.
Do you have any idea what the 4r70w can hold power wise, some people say when built right they can hold 1500, others say anything over 1000 you are pushing you luck.
It really depends on how hard you are on the trans. The planetaries are the weak link and don't take to transbrake beatings as well as others. But then again transbrakes are hard on any trans. It seems hit or miss above 1krwhp but with the new builders more are lasting. I still prefer the ease and performance of the TH400. Keep in mind these trans will need to be serviced at LEAST once a season to keep them running. The TH400 maybe once every two.
Which like I said before I hear it's much cheaper to have the TH400 worked on than the 4R. What gears are you running on your car? What rpm do you get up to on the hwy ?
3.27 with 28 inch tall tires. Highway depends on speed and inclines. It's anywhere from 2,500-3,500. Its kind of like driving a 3.55 26 inch tall tire Cobra around in 4th gear.
Two guys I know had Freddy brown 4r70w transmissions. Twin turbo mach 1 and a twin turbo cobra. Both 8 second cars and driven on the street. Not one had an issue.
FB is the man. I talked with them a lot before I decided to go TH400.
yea hes good. If I go auto, which I eventually will, it will be a FB 4R. I know with the TH400 the sprag can break. 2nd gear. I know there strong as hell. Just not sure how badly the sprag fails. just keep hearing about it
It's easy to do if you slam it down into gears while rolling from what I understand. It's also the most expensive piece to upgrade so lots of people roll on the 34 element sprags and make more than they can handle.
I think for 1500hp the TH400 is more proven and it doesn't require a computer and around town you'll probably never miss the OD. It doesn't have a converter lockup and to me this would be more important than OD.
I have a 4R70 from Silver Fox but I'm making less than 1000hp. It has a multi-disc lockup converter and a Baumann Quick4 shift controller. It's exactly what I want from a street trans but I don't know how much abuse it can withstand at 1500hp.
ks
I have a 4R70 from Silver Fox but I'm making less than 1000hp. It has a multi-disc lockup converter and a Baumann Quick4 shift controller. It's exactly what I want from a street trans but I don't know how much abuse it can withstand at 1500hp.
ks
I debated all these same things and went with the th400. There is only couple guys that seem to have a recipe to make a 1000+ hp 4R reliable, and they are costly. The th400 has more parts available from more manufacturers, and nearly any competent trans builder can take those parts and build it to last. I prefer to work with local guys and not big mail order outfits so I had a local guy build mine and it's been great. As my car has gotten faster, the need for OD has become a thing of the past.
ok so how do these things break? what kind of driving scenario will cause this
A manual valve body isn't like a sequential manual. You can't just throw it from 3 into 2 or 1. It hurts the trans. You basically need to come to almost a complete stop to shift into a lower gear. This is the same for all manual valve body transmissions. The sprag is what takes all the impact of you slamming from a high gear down and they eventually will crap out if you beat on them.
I know very little about transmissions. This is not my area of expertise, I will answer what I know but it's best to talk to a builder when the time comes about what you want and how to use it.
I drop into 1st at 50mph all the time in my th400. The problem is when you downshift under power. That eats the sprag.
The problem is downshifting and hammering the throttle without the sprag catching up. Shifting down a gear must be done while you are off the throttle, then you have to load the sprag back up before you use the throttle again. Otherwise the sprag is freewheeling then you are slamming it with power. Some companies will tell you to not downshift at all while moving lol. A factory trans uses the kickdown to active the intermediate band to help with the downshift. This does not exist in the mvb autos.
Most builders will tell you not to downshift unless under 20-30mph. A reverse mvb is designed to go 1-2-3 not 1-2-3-2.
Most builders will tell you not to downshift unless under 20-30mph. A reverse mvb is designed to go 1-2-3 not 1-2-3-2.
Last edited:
Users who are viewing this thread
