DARF Torque Spec

Forgive me if this has been covered previously, but I have not been able to find an answer through searching the forum and I did not see the spec for these specific bolts anywhere in the service manual.

What is the torque spec for reattaching the metal side plate to the valve body after removing it and performing the DARF? On another website I came across 2-3 ft-pounds(~30 in-pounds), but when I began to work my way up to that I felt like that was too much, and did not want to strip or snap anything. When I removed the bolts they loosened quite easily. I trusted my gut and stopped where I began to feel uneasy going any further. Finished the transmission service and it's running great, shifting smoothly, and no more RSN. I'm planning on draining the pan again another time or two to clear out the junky fluid that was in there(unknown history), and if I can get a definitive answer I will just drop the pan at that time and torque to spec.

I’ve got an ATSG service manual that quotes
4 Nm (35 inch pounds)
for the side cover bolts of the valve body.

-dave
(also gives 71 inch lbs for the solenoid hold down bolts, which I’ve seen elsewhere)

As for lacking in the service manual, the German Mind seems to work on the theory that the "general bolt size vs torque" chart at the beginning of the manual then takes effect.

--dick

ATSG manual

Dougflas said:

ATSG manual

Click to expand...

Thanks... it’s in iBooks on my phone but for the life of me I couldn’t figure out how to export it.
The covers are torqued on page 105, step 23.

-dave

Well, it was bothering me that I possibly hadn't applied enough torque to the 8 bolts holding the side plate onto the valve body and I didn't want to put it off. So I drained the pan and dropped it this afternoon. Backed the bolts out, cleaned everything up, and got out my new 1/4", inch pound torque wrench. Set to 4Nm/35 inch pounds, turning, turning, turning, getting uncomfortable, turning, and DEFINITELY partially stripped out one of the bolt holes. It's in there, but there's no way it's getting to 4Nm without causing more damage. Grabbed a bicycle torque wrench I have, set to 4Nm for comparison on one of the other bolts and it turns out my brand new 1/4" torque wrench is faulty--I was well past 35 inch pounds with no click of the wrench. I used the new wrench for a few other things this weekend and at higher torque it did work properly--seems as though it's issue as at the lower end of it's scale. But that's no excuse, I should have trusted my gut and my hands and stopped. It's embarrassing and I'm not happy with myself right now. The van drives fine, but I'm not going to push it. There's no way I can drive this thing without constantly thinking about that bolt unthreading and doing significant damage.

What do you guys think? New valve body? Tap the bolt hole? Helicoil? Willing to do whatever it takes at this juncture, as anything is a better option than replacing the entire transmission in a few hundred miles.

Nautamaran said:

Thanks... it’s in iBooks on my phone but for the life of me I couldn’t figure out how to export it.
The covers are torqued on page 105, step 23.

-dave

Click to expand...

When you do, please share. The only way I can export from iBooks is via email. Very annoying.

I would feel the same and be inclined to make it proper. I'm sure there's someone here that will offer solution(s).

Retap it to a SAE thread? Or a metric thread?

Bobnoxious said:

When you do, please share. The only way I can export from iBooks is via email. Very annoying.

Click to expand...

Did you try to share it? Hit the rectangle with the arrow at the bottom and then try the more option-share

Dougflas said:

Retap it to a SAE thread? Or a metric thread?

Click to expand...

If you're asking what I would do, I don't have an answer on best course of action. That's what I came here looking for advice on. Obviously, retapping would be easier and less expensive than a new valve body. But a new valve body would be less expensive than a new transmission.

RJV said:

If you're asking what I would do, I don't have an answer on best course of action. That's what I came here looking for advice on.

Click to expand...

Without seeing it, l can not offer a better choice. You are in the valve body, do you have enough meat left to retap it?

Dougflas said:

Without seeing it, l can not offer a better choice. You are in the valve body, do you have enough meat left to retap it?

Click to expand...

Yes, I believe so. The hole that stripped is the single bolt in the middle of the plate. There should be should be plenty of room laterally and horizontally.

When tapping in aluminum, tap to a coarser thread. The threads will be stronger.

Dougflas said:

When tapping in aluminum, tap to a coarser thread. The threads will be stronger.

Click to expand...

Excellent advice, thank you. I wouldn't have known that otherwise.

For the future (and lurkers reading this thread) ...

Whenever i have a torque requirement in units i'm not familiar with (i do "foot pounds") ... i try to convert the new spec to ft-lbs and then assess the *feel* of the wrenching.

35 inch-pounds is "close enuf" to 3 foot-pounds that i'm willing to go with that.

Then, when applying the wrench, i look at the handle length and scale the feel to that ... if it was a 6 inch handle, then it would want 6 pounds. (6 pounds times 1/2 foot = 3 ft-lbs).
On things that *really care* i might even get a fisherman's hook scale and pull based upon that reading.

This same principle can be scaled up, too: if i'm tightening axle nuts that need hundreds of pounds, that merely tells me how far out on the wrench (or extended pipe) handle to place my foot as i apply my full body weight as a "calibrated" force.

--dick (frequently a "mechanic", not a "technician")

Another lesson within this thread: don’t trust the limits of a torque wrench’s scale - stick to the middle third of the range.

Dougflas said:

When tapping in aluminum, tap to a coarser thread. The threads will be stronger.

Click to expand...

Changing thread pitch will change the clamping force achieved for a given torque.
A finer pitched thread clamps more tightly than a courser pitch, all else being equal (they are never equal, of course - there are many moving variables in bolted assembly design...)

I would use a heli-coil to restore the original thread size and pitch then torque the original bolt to spec. This will consume the least metal from the valve body, and because the coil goes into an oversized thread, it will have a slightly larger aluminum cylinder to hold against, making the assembly a bit stronger than before. The steel coil will also resist galling better than the aluminum threads did, so less likely to be damaged during assembly.

-dave

Aside: I don’t worry about integrity of a good insert job. Mercury Marine used to (might still?) use inserts in all their blind holes. Stainless steel and aluminum don’t get along well galvanically and so will freeze together in salt water, so corroded threads are pretty much guaranteed if a stainless bolt is threaded into an aluminum part. With stainless inserts, the outer threads still corrode and freeze, but the inner threads remain clean and serviceable long after. I’ve unbolted carbs from 40 year old outboards and found the bolt threads SPOTLESS.

This is not professional.

I don't recall how tiny those fasteners are.

Form a small hairpin of thin copper wire. Size?? Maybe a strand from a 12 AWG THHN wire. Insert the hairpin legs first into the hole. If too much for the hole size, use one strand. If not enough, add a strand. Keep the wire a bit off the bottom of the hole so the bolt doesn't bottom against it.

Thread the original fastener into the hole until it snugs against the plate. Clip off the leftover copper strands (if they didn't shear off). Button everything up and forget about it.

The method is that the malleable copper wire will force the bolt threads over into the remnants of the aluminum threads. The fastener isn't under great stress while holding the plate in place.

If you don't trust your "feel" with snugging the bolt, use the torque value. If it pulls loose before hitting the torque spec you haven't lost anything. You can still drill and install a repair coil. (My bet is it will hold to torque spec.)

I now return this thread to proper more involved professional answers.

vic

^^...
...or trim a narrow sliver of aluminum foil.

-dave
(who has glued his share of toothpicks into stripped wood screw holes ;-)