Thread: TH 400 problems

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On the inside of the case at the rear there are bumps that hold the snap ring in place between 1st and 2nd gear. Well I sheared them off. Is this due to the added power and or Trans brake or an improper trans build?

Mid section tabs. Some cases don't hold very well under the higher impact of the harsh shifting. There should have been a retention spring put in place to help this condition. Aftermarket springs are the best. Unfortunately the thing is sometimes left out by builders under the belief that it plants a frimer shift or mistakenly left out by over sight. Sounds like it's time to get a new case. Be sure to inspect the thrust area of the rear section before purchasing. This area is often found to be worn out and will create problems of clearancing the shafts as they are assembled. Big no-no. Also, upon assembly of new unit, be sure to properly torque the mid section bolt (12 point bolt through the valve body channel) and if you have any doubts about it's security, GM blue lock tight has good results.

coan makes a part that you can add to the lugs i guess it will help. have one never put it in . it fits in the case were there is open space in the case. with no lungs

if the trans was just built there is a good chance the wrong snap ring was installed in the groove that holds the backing plate. There are two snap rings same size one for the case support one to hold the backing plate. One is square cut one has a bevel. If the one with the bevel was in stalled to retain the Backing plate you've got your cause for the failure.I've seen it a few times.