TH400 Sprag Clutch 1991, new and ready to install. Fits the TH400. Ships fast from the USA.
This listing covers the TH400 intermediate sprag as it applies to 1991 builds: a new 34-element heavy duty sprag made by BorgWarner. 1991 is the year GM's electronic 4L80-E arrived in full-size trucks and vans, and many shops working on a 1991 rig are deciding between a late Turbo 400 and an early 4L80-E. The good news is the intermediate sprag is shared. If your 1991 truck, motorhome chassis or swap project slips in second, flares on the 1-2 shift, or is open on the bench with a damaged sprag, this is the replacement.
The sprag rides between the hub of the direct clutch housing and an outer race that is splined to the intermediate clutch plates. On the 1-2 shift the intermediate clutch locks that outer race, and the sprag elements tilt and wedge so the direct housing, and the sun gear it drives, cannot spin backward. That reaction is what gives second gear. On the 2-3 shift the direct clutch drives the housing forward and the sprag freewheels. In the 4L80-E the same arrangement carries over, with fourth gear added by the overdrive section, so the sprag still does the same job in second.
Check the fluid level and condition, then put a gauge on the line pressure tap so you are not chasing a pressure problem. Road test in Drive and in manual Second. If second is firm only in manual Second, the problem is the intermediate clutch or this sprag. Once the drum is out, hold the outer race and rotate the housing by hand: it must lock solidly in one direction. Look closely at the elements for flat spots and at the hub for ridges. The TH400 common problems guide and the delayed engagement guide cover the pressure and fluid checks to do first.
The listing calls this sprag correct for TH400, 4L80-E and 4L85-E transmissions with non-roller drums, 1964 on. What decides fitment is your direct clutch housing, not the model year: it must have a smooth sprag hub. A 400 fitted with the roller-type intermediate clutch on a cam hub will not accept it without a sprag-type housing. Because 1991 is a crossover year, confirm which transmission you actually have from the case and ID tag, or send us the vehicle, year and VIN. Our TH350 vs TH400 identification guide shows how to tell a 400 by the pan, and the TH400 parts page lists everything we carry for it. If you want the low roller clutch replaced in the same order, the 1991-95 sprag and roller set includes both.
Install the sprag so the housing freewheels in its forward direction and locks against reverse rotation; GM lists a backwards one-way clutch among its assembly faults, so check it by hand before the drum goes in. Replace a pitted or worn outer race, because element rollover usually starts at a damaged race surface. Replace the intermediate clutch plates with the sprag, using a kit such as the TH400 clutch module, and make sure the center support bolt is holding the support tight to the case, since GM lists a loose bolt as a cause of intermediate circuit problems. Twist the drum during installation to index the outer race with the plates. Refill with Dexron type ATF.
| Fits | TH400 1991 |
| Part type | Sprag Clutch |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
1991 is when the 4L80-E arrived in GM full-size trucks and vans, so it depends on the vehicle. Check the case and ID tag, or send us the VIN. This sprag fits both if the direct drum has a smooth sprag hub.
No. The listing is for non-roller, smooth-hub drums. A 400 with a roller intermediate clutch on a cam hub needs a sprag-type housing.
It can be. Read the stored codes, check fluid and pressure, then compare Drive with manual Second. If manual Second holds and Drive slips, the sprag or intermediate clutch is the likely cause.
The intermediate clutch plates, and the outer race if it is pitted. Many builders also replace the low roller clutch while the unit is apart.
Dexron type automatic transmission fluid, the same as the rest of the TH400 and 4L80-E family.
