TH400 Case Busted

[Jim64Cto73B]

I have a 1986 M1008, TH400 behind 6.2. I've run it as a Wildland Fire Truck for 25 years. Transfer Case burst, I replaced the Transfer Case and had front Driveshaft rebuilt. Then Transmission burst and dumped oil. I got the Aluminum Case welded but the Transmission was burnt up. Bought another Transmission that was rebuilt. Replaced Torque Convertor, fresh Oil, flushed Oil Lines and Cooler with Flush, replaced U-joints. Drove Truck 20 miles on highway, Transmission Case busted again. I drove these trucks when I was 64C in the Army, I don't remember Cases Bursting as a problem. Inspecting the truck, nothing presents itself as obvious. Any experience or ideas out there ?

 

[WWRD99]

I have a 1986 M1008, TH400 behind 6.2. I've run it as a Wildland Fire Truck for 25 years. Transfer Case burst, I replaced the Transfer Case and had front Driveshaft rebuilt. Then Transmission burst and dumped oil. I got the Aluminum Case welded but the Transmission was burnt up. Bought another Transmission that was rebuilt. Replaced Torque Convertor, fresh Oil, flushed Oil Lines and Cooler with Flush, replaced U-joints. Drove Truck 20 miles on highway, Transmission Case busted again. I drove these trucks when I was 64C in the Army, I don't remember Cases Bursting as a problem. Inspecting the truck, nothing presents itself as obvious. Any experience or ideas out there ?

I have seen bent drive shafts do that or out of balance.

 

[NDT]

Some TH400s say "HD" on them, make sure you go with one of those next time. Also make sure the bellhousing cover is on.

 

[cucvrus]

Breaking the bell housing of the TH 400 transmission housing is definitely a balance or alignment issue. I had them break when the CV joint breaks on the front drive shaft and it can no longer articulate causing it to push back on the transfer case. Also, out of balance. dented or bent drive shafts. At this point you need to get a good TH 400 case and have the transmission rebuilt by a reputable rebuilder and get both drive shafts sent to a rebuilder and have them balanced. These are NOT new trucks. They have been hacked and beat by everyone along the route of life for over 40 years. Look at everything and do it right the first time. This is NOT a cheap hobby. Have a Great Day,