Rebuilding and Modifying GM Turbo 350 Transmissions for Improved Efficiency

From the Writer

The Turbo 350 may not be as robust as its bigger sibling, the Turbo 400, but it is still a reliable, durable, and capable transmission. Countless GM vehicles have been equipped with this efficient TH350 transmission. Over time, signs of wear and tear may start to appear in your transmission. Eventually, even the most dependable transmissions require a rebuild to maintain their performance.

Revered automotive technical writer Cliff Ruggles guides you thru the complicated rebuild process of GM’s well-liked rear-wheel-drive computerized transmission. Ruggles particulars the step-by-step rebuild and efficiency improve procedures. He consists of instruction on elimination and set up, tear-down procedures, elements inspection, and substitute, in addition to efficiency mods and shift package set up. Time-saving ideas are additionally a part of each buildup.

Instruments & Tools

A roll-around cart makes an excellent place to maintain your rebuild package and different elements clear and separated from the work space.

Elimination

Right here’s a typical drawback with some autos which have a rear-located distributor. If the engine isn’t successfully supported, it might probably lean again and break the distributor cap; in excessive instances it should bend or break the housing!

Disassembly

The used TH350 transmission is secured within the holding fixture and is mounted on the workbench. I’ve cleaned off a piece space and rounded up the instruments wanted to take the unit aside for inspection. This specific unit was fairly clear. Some items require energy washing to take away dust, mud, grease, and street grime earlier than they’re taken aside.

Transmission Fundamentals

The TH400 and TH350 transmissions use a gear-type oil pump. The inside gear is pushed immediately by the hub of the engine’s torque converter. Word that the inside gear is offset within the housing. This creates a chamber that strikes oil and forces it out of the pump.

Meeting

Verify the endplay on every pinion as proven. Additionally spin every pinion and wobble them forwards and backwards. If endplay is past .050 inch, if you happen to really feel any tight spots, or whether it is free on the pins, you need to substitute the planetary meeting.

Shift Equipment Set up

Take away the help plate after which take away the manufacturing facility separator plate. If the transmission is within the car, you can find 4 examine balls above the plate. They won’t be reused as a result of the TransGo shift package accommodates new examine balls.

Efficiency Mods

The aftermarket provides a hardened outer intermediate sprag race as an improve for the TH350 transmissions. It takes extra abuse than the inventory outer race, however can nonetheless fail in a high-torque utility whether it is used with the inventory curler clutch meeting. This occurs just because the load isn’t distributed evenly to the outer race as it’s with the a lot stronger 36-element aftermarket sprag meeting. The (aftermarket) hardened race on this picture survived 71 high-10-second dragstrip runs behind a high-torque 455-ci engine earlier than it exploded.