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· Head of R&D at A1 Transmission
5,630 Posts
Discussion Starter · #1 ·
This is all part of my thread in the Turbo section but I wanted to put a standalone thread with detailed installation info here where there's more traffic. This kit is made by Precision Industries and brought to life for us by Chris Garrett of A-1 Performance Transmission (blower slut) and without him wouldn't have been possible and he is the point of contact for availability and pricing information.

This has already been used and tested in a diesel drag truck setup but whomever had it wasn't very helpful at providing data/feedback to PI about how it worked, etc. Durability will not be of any concern even at close to or over 1K horsepower.

The kit comes as seen here and includes a custom made billet 4WD output shaft.

My transmission had to come out to repair a cracked FWD drum and since the trans must be completely disassembled to install the new output shaft this was a perfect time to install the trans brake kit as well.

After getting the trans back I painted it and made ready to install. The kit uses a stock steel 4x4 tail housing which the brake bolts onto.

Ready to stab in.

Bolted in place. The stock cross member will no longer work due to the 4x4 tail housing mounting location being lower and more offset than the stock 2wd tail housing.

Final installation of the brake needs to be done before installing the trans mount to access all of the bolts. Blue loctite went on the bolts and a stock Ford gasket was used.

Next I had to address the crossmember fitment. Competition Engineering sells a weld up kit that could also be used but I decided to try and modify the stock one to save a little money and see if it would work.

First I cut the welds off the bottom doubler plate and ground it flush.

Next I made two new slots after measuring, the 4x4 tail housing moves the mount towards the drivers side about an inch and is 1 1/8" lower than the stock tailhousing location.

I measured and drilled new holes on the sides as well and used the stock hardware however the top front bolt is no longer utilized and wouldn't be an issue.

I welded the doubler back in and painted it.

Bolted in place. It clears the trailer and I've had no issues on the street thus far so I'm gonna let it ride as is.

It hangs down about 2" lower than stock (flush with frame rails) and is pretty much even with the longbar brackets.

Next the exhaust crossover pipe had to be changed to clear the extra girth of the trans brake. I had material left over from the TT build so it was only a matter of adding another bend and a little welding. I would guess any other system would require similar attention.

The next major area of concern is the drive shaft. A new DS is required that has a slip yoke. I found a place locally to have it done and after asking about components for an aluminum piece he was told the parts were on backorder so to save time (and money) I opted for a steel unit. It's 4" diameter and should handle all the horsepowers.

Up front it requires an output flange for a 5R110 (Ford p/n 2C3Z-4865-BA best I can tell) and the stock rear pinion flange and bolts. The DS shop gave me a bolt in unit so I didn't have to swap anything over and it was $530 out the door.

The supplied output flange is tapped for 7/16-20 instead of the stock ford metric bolts. I sourced some items at work but ARP sells similar for around $15 from Summit.

The brake has clutches inside it that are fed trans fluid via a supplied hose in the kit and requires CO2 pressure to hold the clutches. I already had a CO2 system for the boost controller but due to the pressure and volume required I opted to install another standalone system to operate the trans brake.

I ordered a 5# bottle online and had it filled at the local paintball shop, total cost was under $100 which is cheaper than a 2.5# bottle by itself.

This is the regulator I used. I also ordered a new inlet nipple fitting so it would bolt to a CO2 bottle opposed to nitrogen. There are no high pressure CO2 regulators so this was the only way to obtain the 200+ psi output pressure needed for the brake to hold.

Nitrogen fitting top, CO2 fitting and seal on bottom.

I used some -4 braided line and fittings I already had laying around to plumb the CO2 solenoids and ran it through an existing body grommet.

Both bottles installed and plumbed.

For activation I got a 10amp switch made by TCI from Summit and fabricated a bracket to mount on the steering wheel. I used a 40amp relay I already had to activate the solenoids. They only require one wire supplying 12v to activate and after blowing a 5a fuse testing them I opted to use a relay since I don't know how many amps they pull. I have the feed coming directly from the battery with a 15a fuse and it works fine.

Final test required 225# of CO2 pressure for the brake to hold with the two step set on 4K and seeing just under 11 boosts.


· Believing Believer
2,184 Posts

· Registered
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· Worlds Fastest Street HD Truck
14,724 Posts
love the detailed threads you post!

Interested to see the results at the track and long term. Goodluck man!

· Worlds Fastest Street HD Truck
14,724 Posts
Banks set the bar with 1.37's in a non-brake 4R100 as far as turbo trucks go....lets see some results already! lol
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