Torque converter bolt oops

SlowLane · Post by **SlowLane** » 18 Jul 2020, 17:13

I opted to buy one of the PNH reman torque converters from Triple Edge along with the transmission rebuild kit. Before installing the converter I chased all the mounting holes with a tap to clean out the paint and other gunk, but one hole was harder to chase and actually yielded some metal. I should have taken better note of this at the time.

Fast forward to this morning when I'm torquing the torque converter bolts down to 50 Nm, and whaddya know, one of them isn't getting there. It's snug, but has clearly stripped and is holding at about 30 Nm.

Okay, one stripped bolt out of six. It's so tempting to just leave it in, or re-insert with red loctite, but I expect that's the wrong thing to do if I want to keep driving this car without worrying about a loose bolt rattling around behind the flex plate.

So I guess the trans has to come out again. Ugh.

Asking for recommendations on repair: Helicoil, Time-Sert, re-drill for larger bolt? Get another torque converter? Re-install my original converter?

Thanks

Post by **RickHaleParker** » 18 Jul 2020, 17:52

Check to see if there is a SAE size between the bolt size and next metric size up. You might be able to tap a SAE size without drilling and it would not remove as much material.

Post by **abscate** » 18 Jul 2020, 18:12

I’m a risk taker so I would red loctite it at 30 Nm

Post by **volvolugnut** » 18 Jul 2020, 18:37

RickHaleParker wrote: ↑18 Jul 2020, 17:52 Check to see if there is a SAE size between the bolt size and next metric size up. You might be able to tap a SAE size without drilling and it would not remove as much material.

Agree with larger bolt size - SAE or metric. Else use a Helicoil.

volvolugnut

SlowLane · Post by **SlowLane** » 18 Jul 2020, 23:58

Thanks for the suggestions. The bolt size is M8x1.25, with only about 9 mm of thread engagement, even though the torque converter has about 13 mm of thread depth. I'm tempted to use longer bolts, but would need to match the head diameter and height of the T50 Torx screw Volvo uses. The fastener is a Class 10.9, so I would need to find a equivalent strength bolt if I were to use a different bolt size. I'm checking Bel-Metric's offerings.

Nearest SAE equivalent is 5/16", which is a hair less than 8 mm, The next common SAE size up is 3/8", which is so close to 10 mm that I would just go up to 10 mm if I were to decide to use different thread.

I'm going to take a chance on a Time-Sert kit. They have always seemed to be a better system than Helicoil to me, but I guess I'll find out once I install it and torque-test it. I'll know better once I have the Time-Sert kit in hand, but it looks like if the M8x1.25 Time-Sert fails to do the job, then re-tapping for an M10x1.25 bolt ought to be feasible, as the advertised diameter of the M8 Time-Sert tap is slightly smaller than an M10 tap. Fingers crossed that is the case.

Geno9707 · Post by **Geno9707** » 19 Jul 2020, 10:51

Hello contact me I can ship you some torque converter bolts. [email protected]

SlowLane · Post by **SlowLane** » 19 Jul 2020, 13:02

Geno9707 wrote: ↑19 Jul 2020, 10:51 Hello contact me I can ship you some torque converter bolts.

Thanks, but sourcing new bolts isn't a problem. There are plenty of places to get them.

SlowLane · Post by **SlowLane** » 26 Jul 2020, 10:07

Okay, quick update.

Discovered that TIme-Serts are absolutely worthless in high-torque applications like this. Before installing the converter I did a test torque on the Time-Sert repair and it failed well before getting anywhere close to 50 Nm.

Fortunately the busted TIme-Sert came out easily enough, in several pieces, with an Easy-Out.

I then threaded a Helicoil into the hole (Helicoil and Time-Sert use the same over-size tap, at least for the M8x1.25 size). The Helicoil did hold up to the 50 Nm, but just barely, and it was pretty iffy getting there. Unfortunately the counter-bore which needed to be cut for the failed TIme-Sert reduced the number of effective threads that the Helicoil had to work with, so I'm not at all confident in its long-term viability when put into service.

So I've decided to just re-install my original torque converter. It had not been giving any indication of problems before the transmission broke. I had only ordered the reman unit because I figured that after 200,000 miles it would be prudent to replace the converter as part of an overall drive-train refresh. Expensive lesson. Silly me.