TH350 Rebuild Cost and What Drives It

Ask three shops what a Turbo 350 rebuild costs and you will get three different numbers, and all three can be honest. The TH350 is one of the cheapest automatics GM ever built to overhaul, because the soft parts are made by the ton and the unit has no solenoids, no computer and no adaptive learning to sort out. What moves the price is not the kit. It is what the teardown finds: a cracked intermediate overrun race, a scored accumulator bore, a worn servo bore, a burnt sun shell, a plugged cooler. This guide breaks a TH350 rebuild into its real cost buckets so you can read an estimate, or plan your own build, without being surprised halfway through.

All prices quoted below are current parts prices from our own TH350 shelf as of October 2026, so you can see real numbers instead of ranges pulled from a cost calculator. Labor is the shop's rate times the time they bill, and we will cover how that works too.

Recommended TH350 parts

The core of a TH350 rebuild budget: a 1969-86 master repair kit with frictions, a replacement sun shell for the most common burnt hard part, and an overhaul gasket and seal kit. Ships from the USA. Secure checkout.

ATP SMS-9 TH350 Master Repair Kit Plus (1969-1986 GM)

$321.99View part

TH350 Sun Shell

$139.98View part

TH350 Overhaul Kit 1969-1986

$85.32View part

Bucket 1: The Soft Parts Kit

Every rebuild starts here. A TH350 kit comes in three common levels, and knowing which one is on the estimate tells you a lot about the job.

• Overhaul (gasket and seal) kit. Gaskets, lip seals, metal and Teflon sealing rings, and O-rings. No frictions, no steels. Our TH350 overhaul kits for 1969-1986 units run about $85. This is enough for a reseal or for a builder who is reusing a known-good clutch pack, which on a worn-out unit is almost never.
• Master kit. The overhaul kit plus a full set of friction plates, and usually the band and filter. The ATP SMS-9 master repair kit covers 1969-1986 units and sits at $321.99 on our shelf. This is the normal rebuild kit for a stock street unit.
• Master kit with steels, or "Pro" kits. Adds new steel plates and sometimes bushings. Worth it on any unit that was run hot. Blued or warped steels are a common reason a fresh rebuild slips again, and replacing a full set of steels as a separate purchase usually costs more than buying the kit that includes them.

Read the model code on the case before ordering. Early and late TH350 units differ in clutch counts and pump parts, and lockup TH350C units from 1980 on use different pump and sealing parts. Our TH350 rebuild wear points guide covers plate counts by unit.

Bushings are a line item, not an option

Transmission Digest's guide to quality rebuilding says it plainly: replace the bushings. Bushings keep the rotating members on center and meter lube oil, and some of them act as seals. The article calls out the front stator support bushing, which controls converter-apply oil, as one that seals pressure. A TH350 has more than a dozen bushings and is known for eating the ones in the sun shell and direct drum. A complete TH350 bushing kit is a small spend compared to a comeback, and if your estimate says "bushings as needed," ask which ones were measured and how.

Bucket 2: Hard Parts the Teardown Finds

This is where two TH350s with the same symptom end up hundreds of dollars apart. These are the hard parts that most often get added after the unit is on the bench, roughly in the order a rebuilder finds them.

Intermediate overrun clutch outer race

Sonnax states that race failure "is a chronic problem with TH350 transmissions." The OE race (GM 6261021) cracks at its radial lube holes and spline stress points. When it lets go, the symptoms Sonnax lists include intermediate clutch failure, 1-2 slip and delayed engagement, and in the worst case a destroyed case. Its replacement, part 35723HD-02, is rated at twice the torque capacity of an OE race. On a unit that slipped 1-2, assume this race is suspect until it is inspected. On any unit behind a modified engine, plan to replace it regardless.

1-2 accumulator bore

The 1-2 accumulator piston strokes on every upshift, and Sonnax notes that the TH350 and TH350C case bore wears or scores "from repeated oscillation during normal operation." That leaks off line pressure and shows up as low line pressure, 1-2 slip and delayed forward or reverse engagement. The money point is this line from Sonnax: once the bore is damaged, the case must be thrown away unless it is sleeved. The Sonnax 1-2 accumulator sleeve kit (35719-01K) saves the case. A sleeve kit is a modest add. A used core case, plus the labor to swap everything into it, is not.

Intermediate servo bore

The same wear happens at the intermediate servo. Sonnax describes case bore wear and oil loss at the servo, and lists the results: no engine braking in manual second, low line pressure in Reverse, Neutral and Drive, and delayed engagement. Their 35709-01K sleeve kit is a drop-in that needs no machining of the case. On a high-mileage unit with a soft-everything pressure complaint, this bore and the accumulator bore are the first two places a good rebuilder looks, which is why they belong on the estimate as "inspect, sleeve if worn."

Sun shell, planetaries and drums

A TH350 that was run low on fluid or overheated often comes apart with a sun shell whose splines or bushings are gone, a front or rear planetary with worn pinion bushings or thrust washers, or a direct drum with a cracked or worn bushing bore. These are not kit parts. On our shelf a TH350 sun shell is $139.98, planetaries run about $56 to $76, and direct and input drums run roughly $70 to $190 depending on year and supplier. A unit that needs a sun shell, one planetary and a drum has just added $250 to $400 in parts before labor.

Pump

The pump body and cover wear at the gears, the bushing and the stator support. Small wear is fixed with a bushing and a careful inspection of the gear pocket. A scored pocket or a worn stator support means a replacement pump, which runs about $175 for a 1980-86 unit and $280 to $460 for early units on our shelf. Transmission Digest also tells rebuilders to check pump halves, valve bodies and the case for flatness, because warped parts cause cross leaks that are hard to diagnose. A warped pump half is a common reason a "rebuilt" TH350 never shifts right.

Bucket 3: Converter and Cooler

A rebuild that reuses a converter full of clutch debris, or a cooler packed with it, is a rebuild that comes back. Plan for both on the estimate:

• Torque converter. A TH350 converter is a welded unit and cannot be cleaned out completely in the field. If the old unit failed with friction or metal debris, a rebuilt or new converter is standard practice. A TH350C lockup converter with a glazed or shuddering clutch has to be replaced or rebuilt for the same reason. Our TH350 lockup shudder guide covers how to tell.
• Cooler. GEARS magazine (ATRA), in its article on R&R do's and don'ts, says to flush the system correctly with dedicated equipment and to replace a failed cooler instead of reusing it, because a contaminated or restricted cooler puts debris straight into a fresh unit. On a TH350 the cooler is usually in the radiator tank, so a plugged one can mean a radiator or an auxiliary cooler added to the bill.

Bucket 4: Upgrades You Choose

None of these are required for a stock rebuild, but they are the most common way a TH350 estimate grows by choice rather than by surprise:

• A shift kit or recalibrated valve body for firmer shifts. A shift kit is around $60 to $105. A full replacement valve body costs a few hundred dollars, and full manual race bodies run past $700.
• The HD intermediate overrun race on a healthy unit, as insurance.
• A 4-wide or 5-wide intermediate or direct clutch setup for more holding capacity.
• An adjustable vacuum modulator ($33.99 on our shelf) so line pressure can be set for the engine's real vacuum, which matters on cammed engines.
• A deep or finned pan and an auxiliary cooler for towing or heat.

Ask for upgrades as separate line items so you can see what you are paying for the rebuild and what you are paying for performance.

Bucket 5: Labor, and How It Is Billed

Labor is usually the biggest single number on a shop rebuild. The FTC's auto repair guidance explains the two ways it gets billed: a flat rate based on an independent or manufacturer's estimate of the time the job takes, or the actual time the technician worked. A TH350 is a simple, fast unit to R&R on most older GM cars and trucks, so the variables are the vehicle (exhaust, crossmember and shifter linkage on a lowered or swapped car take longer than on a stock C10) and the bench time, which goes up with every hard part and sleeve kit added.

The FTC also says a written estimate should identify the condition to be repaired, the parts needed and the anticipated labor charge, and that a shop should contact you for approval before doing work that goes over a specified amount. On a rebuild, that approval call usually happens right after teardown. That call is where the hard parts in Bucket 2 get added, and it is the moment you should ask to see the cracked race or the scored bore.

DIY vs Shop: Where the Money Actually Goes

For someone doing their own TH350, the parts math for a stock street rebuild looks like this:

• Best case: master kit, bushing kit, filter, fluid. Roughly $350 to $450 in parts.
• Typical high-mileage unit: add the HD overrun race, one sleeve kit and a planetary or drum. Roughly $600 to $800.
• Burnt unit: add a sun shell, pump, converter and cooler. It is easy to pass $1,200 in parts, and at that point a good core or a complete rebuilt unit deserves a look.

DIY also needs tools that a shop already owns: a clutch spring compressor, a pump alignment band, a holding fixture, a dial indicator for endplay and a bushing driver set. If you only plan to do one transmission, factor those in. Transmission Digest's rebuilding guide adds the steps that keep the unit from coming back: soak frictions in ATF for 15 minutes before assembly, set clutch clearance at about 0.008 to 0.010 inch per friction plate, check endplay, use a torque wrench, and air-check every circuit as you go.

How to Read a TH350 Rebuild Estimate

1. Which kit level is listed: overhaul, master, or master with steels?
2. Are bushings replaced, or only "as needed"?
3. Is the intermediate overrun race inspected or replaced? Is the HD race quoted?
4. Were the 1-2 accumulator and intermediate servo bores checked, and is a sleeve kit priced if they are worn?
5. Is the converter new, rebuilt, or reused?
6. Is the cooler flushed with equipment, or replaced if it failed?
7. Is labor flat rate or actual time, and what is the approval limit before extra work?
8. What does the written warranty cover? The FTC notes there is no "standard warranty" on repairs, so get the terms in writing.

A low quote that leaves out bushings, the race, the bores and the cooler is not cheaper. It is a second rebuild with a delay on it.

FAQ

How much does it cost to rebuild a TH350 transmission?

For a do-it-yourself stock street rebuild, parts run roughly $350 to $450 in the best case: a master kit, bushings, filter and fluid. A typical high-mileage unit that needs the overrun race, a sleeve kit and a planetary or drum lands around $600 to $800 in parts. A shop adds labor billed either at a flat rate from a time guide or at actual hours.

Is a TH350 cheaper to rebuild than a 700R4 or 4L60E?

Usually, yes. The TH350 is a three-speed with no overdrive, no solenoids and no computer control, and its kits and hard parts are produced in huge volume. Cost rises when the teardown finds a cracked overrun race, worn case bores or burnt gear train parts.

What hard parts most often add cost to a TH350 rebuild?

The intermediate overrun clutch outer race, which Sonnax calls a chronic failure point, the 1-2 accumulator and intermediate servo case bores, which wear and leak line pressure, and the sun shell, planetaries, drums and pump on units that were run hot or low on fluid.

Should the torque converter be replaced during a TH350 rebuild?

If the old transmission failed with friction or metal debris, yes. A converter cannot be cleaned out completely in the field, and reused debris will damage the fresh unit. Flush the cooler with proper equipment, or replace it if it failed, for the same reason.