TH200-4R Rebuild - No Nonsense 900

The 200-series transmission, which came into being in the late 1970s, evolved from the limp-wristed 200 and 200C 3-speeds into a 4-speed auto with overdrive that sat behind the most powerful American car made in the 1980s. The 200-4R wasn't bolted to some low-torque wussy motor like the 5.0 Ford--it sat behind the LC2 3.8-liter V-6, powering the bad-boy Turbo Buicks and the Turbo Trans Am. These little mills put out 300 foot-pounds of torque to the wheels stock. And how many stock TRs or TTAs have you seen lately?

Nope, chances are that most of these transmissions have spent the last 15 years or so dealing with 20 pounds of boost and 400-500 ft.-lbs. at the wheels--day after day, shift after clutch-frying shift. If you're driving around with a stock TH200-4R with 100,000-plus miles on it, chances are it needs some TLC. This is a damn strong tranny for factory standards, but when the ETs start to dip into the low 12s, many of the low-rent GM internals just can't cut it. The unhardened pump stator support can fail, the direct (third-gear) and low reverse clutches start to flake apart, and insufficient fluid pressure causes excessive wear on the second gear band and the third gear direct clutches.

But the 200-4R has tons of positive qualities: a light assembled weight, low power loss through the trans, optimally spaced gears, and a .67 overdrive for fuel economy and low highway revs, to name a few. Simply put, it's a great transmission that's just aching for a good rebuild--and that's where Dynotech Performance comes in.

If you are looking for a list of proprietor Eric Schertz's impressive credentials when it comes to building GM trannies, give him a ring. We think the only thing you need to know is this: 9.57 at 141. That's how fast Schertz has gone with one of his 200-4Rs, a number that until recently was the property of the heavy and inefficient 400 3-speed. Eric's Stage 2 Turbo Buick puts down 701 horses and 759 ft.-lbs. to the wheels--that's over 900 at the flywheel, all with a Hi-Pro transmission!

So with that in mind, I couldn't wait to head down to Manville, New Jersey to get the '87 T on Dynotech's lift. When I bought this car 11 years ago, the 200-4R was untouched, and I left it that way. Which means that the original BRF trans and the D5 torque converter have 157,000 very hard miles on them. The duration between the 1-2 and 2-3 shifts has gone from a relatively acceptable shift to a bad, long, slipping shift--not great for the quarter-mile mambo.

A highway run above 55 miles per hour results in a severe vibration that we're pretty sure wasn't there from the factory. And shifting into Reverse results in a CLUNK--not cool. Nothing wilts a car guy's virility like a soft-shifting tranny, but Dynotech has got a rebuild that will rock the Hydra-matic's world--the $1495 Hi-Pro. The shop even offers a 12-month/12,000-mile warranty against clutch burnout or pump failure with this rebuild. Yep, this is having your cake and eating it too--probably the last performance trans you'll ever have. So check out part one of this story, as Dynotech's crew removes and disassembles my ailing 200-4R.

When the time comes to rebuild a GM transmission for a high-performance application, a handful of builders are mentioned over and over for quality, reliability, performance, and customer service: up north, you hear Finish Line Performance. Down south, it's Century Automotive.

Out west, Performance Transmission Services is the word. And on the East Coast, if you're looking for a stock rebuild or a trans that lives into the mid-9s, you head to Dynotech Performance. My TH200-4R's time had come, but Dynotech would make it better than new.

Tech Jim Madison begins the removal procedure by disconnecting the TV cable attachment at the throttle body.

Once under the T, he disconnects the rear U-joints from the driveshaft. Jim pulls the shaft from the transmission and slides it rearward, out of the way of the trans.

The B&M shifter cable bracket is unbolted from the trans pan. It's tied out of the way to avoid damaging the bracket when the trans is dropped down.

The speedometer cable is unscrewed, then the TCC lockup harness on the driver side of the trans is unclipped...

and the electrical connector is unhooked.

The cotter pin and washer for the neutral safety switch linkage arm is removed, then the arm is slid out the back.

Madison uses a 10mm ratchet to remove the four torque converter cover bolts, then a flywheel tool and a 15mm end wrench are used to remove the three torque converter bolts.

Fifteen millimeters is also the magic number to remove the trans mount nut. With that gone, the mount can be removed from the crossmember.

"This is the perfect trans jack for your car," Jim states. Why? "Both of them leak bad."

Two 15mm bolts are removed to take the trans mount off of the transmission.

A single 10mm bolt is removed to disconnect the TV cable from the trans.

It takes a 1/2-inch flare wrench to disconnect the trans cooler lines.

Next, the six 9/16-inch bellhousing bolts are removed with the air ratchet and a 2-foot extension. A ground strap on the top driver-side bolt comes off when the bolt comes out. Don't forget that during reassembly!

After one last look to double-check that everything was out of the way...

Madison slowly dropped the TH200-4R down.

With the stock D5 converter removed we took a close-up look at the stator, which has lost a significant amount of material from the splines. "You were just barely holding on there, pal," Jim remarks. "Probably all the extra trans fluid around the bellhousing that kept you going." Alright smartass, enough leak jokes.

Over on Dynotech's bench, Eric Schertz starts the disassembly by removing the check ball capsule, the factory servo, and its sealing rings. The linkage arm goes next, then a plastic clip, then the speedo gear and its housing.

Sixteen trans pan bolts and seven pump bolts are 13mm, they come out next.

A look at our trans pan after a fluid change only 5,000 miles ago. Eric says "the amount of black clutch material, with that mileage on your fluid, shows excessive wear."

Four 13mm bolts are removed to pull the governor housing and the governor itself, then 15 10mm valve body bolts, four 1-2 accumulator housing bolts, and one stiffener plate bolt are removed.

Eric is removing the TV spring, ball and pin assembly to reduce any chance of a second-gear start condition due to the increased pressure of the transmission. The lockup case connector is removed as well, using a 3/4-inch wrench.

The 1-2 accumulator housing is removed, and Schertz finds a good spring inside.

The valve body, separator and stiffener plate are removed.

The fourth gear accumulator spring and piston came out next.

The fourth gear accumulator spring and piston came out next.

Two 10mm center support bolts are the last ones needed to be removed from the trans case.

Three physical components make the GN 200-4R different from the lesser models: the BR-coded valve body, the BR-specific governor, and the 694 servo.

The 16-year-old lockup solenoid is clipped off; it will soon be replaced with an aftermarket, higher flowing solenoid.

A pump removal tool pulls the pump off. The old pump O-ring and gasket are discarded, then the pump washer and the oil slinger are removed.

The overdrive snap ring is removed next.

Next, the overdrive clutch pack, the overrun drum and overdrive planet assembly, and the overdrive ring gear and washer come out.

It's the overdrive piston retainer's turn, with the overdrive piston return spring and overdrive piston.

The center support tapered snap ring comes out next. Eric "walked" the direct drum center support out with a pull tool and a hammer.

Black, embedded with metal particles and reeking of burnt Dextron--yep, the factory second gear band is shot.

Schertz checked the drum for flatness using a straight edge, and amazingly, it still had a flat apply surface--critical for band engagement. To the untrained eye, the drum appears to be in bad shape. "Close your eyes and feel the surface," Eric urges. To clean it up, a square of 400-grit sandpaper makes quick work of the ugly surface, returning it to good as new.

A look inside of our drum shows the sealing ring surface, which has some wear grooves from the worn sealing rings.

Dynotech uses a wheel brake cylinder hone that gets rid of the wear in the drum.

The washer and band anchor come out, then with snap-ring pliers, Schertz removes the output shaft snap ring. Once that's gone, the ring gear, the front planet, and the sun gear come out in that order. The sun-shell-to-center-support washer comes next.

Another tapered snap ring, this one holding the low reverse center support housing, is snapped off. A center support removal tool pulls out the low reverse center support.

After another snap ring, the low planet assembly comes out--the low reverse clutches, the low planet assembly, and the ring gear. Eric knocks out the low reverse case seal last.

With the 200-4R autopsy underway, it's time to identify the ruined parts: from left to right, top to bottom, the overdrive clutches and steels are burned and overheated, the forward clutch wave steel and top plate are warped and overheated. The direct clutches, steels, and top plate are burnt and overheated. It has worn bushings, worn-out direct clutch sealing rings, a worn-out thrust washer, worn and collapsed springs on the low/reverse spring and roller, a burnt and flaking band lining, an 80 percent worn stator support, and more worn bushings. Finally, the low reverse spring and roller assembly (commonly known as a one-way clutch) exhibited worn, partially collapsed springs.

All of the wasted parts are trashed, then the trans case and a basket full of reusable hard parts get tossed into a parts cleaner to remove 17 years of grime.

With the trans removed, Dynotech does an inspection in that general vicinity. Jim tests the flywheel by lightly tapping it with a hammer. If it 'rings' like a bell, that indicates a sound flywheel. A dull sound could mean it's cracked.

Madison reaches up to the motor to feel the intake manifold seal, making sure that it is still pliable and not hard as a rock.

Time to clean our pipes. Compressed air is used in one trans cooler line, with a bottle on the other end, to clear out both lines.

Then a can of Trans Flush is run through to thoroughly clean out the lines.

The driveshaft's front yoke showed some wear, but it was sanded down to an acceptable condition with 200-grit sandpaper.

An original front U-joint had seen better days, and the rear U-joint had a limited range of movement, so I decided to replace both. Mike used a torch to melt the injected nylon holding the joints--if you do this yourself, just heat the nylon up enough to get it out. Sometimes they'll go flying if they get too hot. Replacement GMB U-joints were installed.

All grime aside, the original transmission mount didn't look too bad on the surface--but the rubber had separated, and this factory replacement mount should drop the high-speed vibration down quite a bit. The Buick was as ready as it would ever be, so check us out next time as Dynotech builds us a 900-horse-capable 200-4R.