Muscle Mustangs & Fast Fords
One-Day DIY Torque Converter Install on a 2013 Ford Mustang GT, Part 4
We find a weakness in our Roush blown 5.0 the hard way and do an expert torque converter upgrade.
Installing Precision Industries Torque Converter
On our way to the Joliet, Illinois for the NMRA event, we detoured to Lead Hill, Arkansas. Buried deep in the Ozark mountains with a population of less than 300 people lies BTS Transmissions, also known as Brian's Truck Shop. Brian Thompson, owner of BTS, is one of the smartest guys on the planet when it comes to bulletproof transmissions.
Awaiting us at the state-of-the-art facility was a shiny, new Precision Industries 9.5-inch, billet, triple-disc converter (PN 509018-3) with a custom BTS 3,400-3,600 stall speed. It should be aggressive enough for the track and mild enough for street driving. The installation was straightforward, however, we do have a few tips to help your install go smoother.
To simulate the average Joe's garage conditions, we installed this baby on our backs with the car on jackstands. We began by using a 13mm stubby wrench for the two transmission top bellhousing bolts easily accessed from under the hood. Next, we removed the transmission rear sensor connection, which has a simple twist-lock design. Then we removed the trans using a trans- mission floor jack with a piece of Styrofoam to stabilize the transmission during the converter swap, as well as protect the oil pan.
The factory converter uses studs with nuts to bolt to the flexplate. The PI converter used bolts instead. After installing the converter in the transmission, we measured the depth of the converter to make sure it was fully seated. We reinstalled the bellhousing bolts, starter, driveshaft, and exhaust.
The transmission requires Mercon LV Ford transmission fluid, and we added four quarts to reach the fill line. Here's a little tip—we recommend you purchase a fluid transfer pump to help fill the transmission, because you have to do it underneath the car due to Ford not having a fill tube that reaches the engine bay.
With the transmission back in and everything buttoned up, I took her out for a spin. The driveability was incredible considering the stall this converter has. I expected something a little more aggressive, but the looseness was barely noticeable.
As a newbie bracket racer, one thing I have struggled with is the ability to stall the car at a higher rpm (above what the stock converter would allow) in order to bump myself into the proper stage depth (I generally stage to hit the Pro tree). Before the converter install, I had to worry about pushing through the beams if it was stalled beyond 1,700 rpm, which made it difficult to work on reaction times. My bump-in is much more controlled now—I have a lot more confidence at the line that I won't go red when I'm trying to cut the Tree on my opponent. Immediately, I was able to stall the new Precision/BTS converter up to 2,800 without feeling the front tires start to scoot out from under me.
On track, we saw a solid 0.1 gain in overall e.t. from the converter swap alone. We monitored the conditions closely with our trailer-mounted weather station. During a test at our local track with the factory converter, the DA (density altitude) was showing 2,000 feet (corrected DA) and we made several 10.90 passes. In Joliet's 3,500-feet corrected-DA weather conditions, we ran back-to-back 10.80s at high 120s all weekend. So, while there was a 0.10 improvement on the clocks, there would be a bigger drop in e.t. had the weather been equal to our baseline test.
To remain safe and legal, we went ahead while we were under the car, and installed a Granatelli Motorsports driveshaft loop (PN GM-DSL0507), retail price $183.75. The car still has a factory two-piece driveshaft and this will keep the driver safe in the event of a failure. The installation on the driveshaft safety loop was easy and self-explanatory.
Our future plans include a ported elbow and a larger throttle body to squeeze more boost out of the Roush supercharger, as well as an off-road X-style mid-pipe, and possibly a gear upgrade.
Our suspension friends will probably kill me for saying this, but why would we change a thing when it's easy to achieve high 1.4 60-foot times? Dead-hooking on the factory goodies is a great problem to have! We will start modding the suspension components when the rubber quits biting like a rabid animal. We're looking forward to killer air at the Bowling Green NMRA event, so check back for the latest on our Roush coyote buildup.
Just before this story went to print, we made one last trip to the track. To our pleasant surprise, after mid-and high-1.5 60-foot times, we had finally broken into the 1.4s with a 1.49—on stock suspension and 3.15 gears! That same run yielded a 10.79 e.t. at 128.57 mph. DA was above 2,300 feet, so conditions weren't optimal.