Stripped TH350 transmission bolt
Thread Starter
Instructor
Joined: Apr 2009
Posts: 160
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From: Gorey Ireland
Stripped TH350 transmission bolt
Installed my new champion cooling 2-row alloy radiator the weekend and while I was at it I changed the filter in the Th350. Trouble is, a few pounds from the torque setting I stripped one of the bolts and now I have a small leak there 
Is using a helicoil kit the best option to fix this? If so, anyone know what size helicoil kit to get (or even better, a link to the correct one?)
On a positive note, the new radiator looks lovely under the hood!
Is using a helicoil kit the best option to fix this? If so, anyone know what size helicoil kit to get (or even better, a link to the correct one?)
On a positive note, the new radiator looks lovely under the hood!
Le Mans Master
Joined: Dec 2007
Posts: 6,422
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From: McHenry Illinois
Last edited by '75; Sep 25, 2011 at 04:26 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Using a helicoil is the best way to fix your problem. But, it is a bit difficult to get your drill positioned truly vertical so that the bolt will be straight. Also, the aluminum case is very soft and the drill will want to bite and take off on you. To prevent this, spend $5-10 for some drill stops (collars that lock onto the drill bit to set the max depth of the drill). This will prevent "over"drilling and will free up your mind to focus on keeping the drill bit straight.
For screw threads that are going into a blind boss, you need to measure the depth of the hole (smaller drill bit and mark the depth), then set the stop collar so that your drill will not go any deeper. Also, buy Heli-coils that are only 1.5 diameters long. You will not get longer ones to fit into the blind boss holes. Use a T-handle with your tap; it will help keep you straighter than a side-handles driver.
On a scale of 1-10, for an average home 'mechanic', this job is a 3-4, if you are careful and use the stop collar. If you don't use a collar, this job can quickly turn into a 6-7 job.
P.S. You should heli-coil any holes that feel even a little bit weak. That way you won't have a problems after the fact. Also, do not tighten these bolts any more than GM specified max torque. (This value is in INCH-pounds....not foot-pounds.)
For screw threads that are going into a blind boss, you need to measure the depth of the hole (smaller drill bit and mark the depth), then set the stop collar so that your drill will not go any deeper. Also, buy Heli-coils that are only 1.5 diameters long. You will not get longer ones to fit into the blind boss holes. Use a T-handle with your tap; it will help keep you straighter than a side-handles driver.
On a scale of 1-10, for an average home 'mechanic', this job is a 3-4, if you are careful and use the stop collar. If you don't use a collar, this job can quickly turn into a 6-7 job.
P.S. You should heli-coil any holes that feel even a little bit weak. That way you won't have a problems after the fact. Also, do not tighten these bolts any more than GM specified max torque. (This value is in INCH-pounds....not foot-pounds.)
Last edited by 7T1vette; Sep 25, 2011 at 08:22 PM.
