quick question on removing torque tube

[Highside]

Yes, I just bought a 1970 opel Gt, and the central support rubber is in real bad shape. So I have started the process according to the manual on removing the central support.
Question?
The bolts that attach the torque tube. What tool is used to take the bolts out? Is this a standard allen head? I put a metric one in the bolt last night, and it felt to loose. I didn't want to mess up the head until I knew the size.
I have notice that several bolts on this vehicle seem to be metric, but the allen heads on the rear differential felt like they would strip if I tried to loosen the bolts. Also, IF I decide to replace these bolts with some grade A's, is this a metric thread?

Ones I know the correct size allen head, I will probably use my impact driver with the allen head to loosen the bolts.

thanks,
Rick aka Highside

[markandson]

They are metric 12 point star bolts, you can buy the tools at any good supply house. Do a search for "star" or "12 point" and I am sure you will find multiple threads that have discussed these bolts before.

[Highside]

thanks.
Ya, I tried to look through threads for this answer, but I will look again.
I'm new to the opel world, but not to mechanics and fabrications.
thanks again.
Rick

[namba209]

I'm gonna presume you already have the drive shaft out of the car. So I'll just say, watch the location of the large washers under the torque tube mounting plates where the bolt in to the body. Those are 15mm bolt heads IIRC. The donut can be a bear to change, I used commercial grade vaseline to get mine in. You'll have to bend the locating tabs just a bit to get it out and again to hold the donut in place. I would also suggest whle you're at it to get the rest of the rubber parts that go in that area. Opel GT Source --- Welcome has all the parts you'll need to do the job. HTH.

[GTJIM]

Yep - those four torque tube bolts back around the pinion are originally 'Tri-square' or '12-point' heads - the thread is the standard M8 X 1.25mm pitch (from memory!) so they can be replaced with conventional Metric Allen Head capscrews of grade 10.9 or better.

[P.J. Romano]

I replaced the torque tube bolts with 14mm hexagonal head bolts that were easy to get in a hardware store.
Also, I found that the donut became quite soft and manageable after I warmed it up in a hot water.

[GTJIM]

Originally Posted by P.J. Romano I replaced the torque tube bolts with 14mm hexagonal head bolts that were easy to get in a hardware store.

Those hardware store bolts are probably just low tensile ones - have a look on the hex heads and see what is stamped there - if it is nothing or '4.8' then they are low grade bolts that are just not strong enough for the job.
Good metric bolts come from specialty bolt shops ... or McMasterCarr ... and should have a grade number of 10.9 stamped on them.

Metric Grades go >> unmarked >> 4.8 >> 8.8 >> 10.9 >> 12.9 with each larger number equating to higher tensile. Allen Head capscrews usually start at 10.9 and 12.9 tensile so that is why they are recommended for critical load-bearing applications. Still, you have to check because there are lots of cheap junk on the market pretending to be 'good stuff' till you closely examine them. Their tensile spec is usually stamped around the outside of the head next to the shoulder.

[heimue]

One little bit of advice here, as a general note: A higher grade (higher strength) bolt is not always a better bolt. A higher strength bolt has a smaller lengthening when tightened --> You have to tighten it more, or it will come loose! The thing is, the tap where you screw it in might not hold the higher load, and you ruin the tap.
--> Always check the original bolt, and replace it with the same strength bolt.
--> If you are using bolt-nut connections, pair them right too: a 8.8 bolt goes into a grade 8 nut, a 10.9 bolt needs a grade 10 nut, 12.9 into 12... (you get the picture).

Dieter

[P.J. Romano]

Originally Posted by GTJIM Those hardware store bolts are probably just low tensile ones - have a look on the hex heads and see what is stamped there - if it is nothing or '4.8' then they are low grade bolts that are just not strong enough for the job.

Just checked those bolts. They are 8.8. They seem to be doing the job but I will order new from OGTS.
Thanks for the tip.

[GTJIM]

Originally Posted by P.J. Romano Just checked those bolts. They are 8.8. They seem to be doing the job but I will order new from OGTS. Thanks for the tip.

"8.8" is Metric medium tensile and should do the job - as long as the underneath head of the bolt sits squarely on the torque tube where the area around the bolt hole is contersunk and flattened.


... still, it is better to have the correct capscrews - so OGTS is a good idea!