Bolt Torque Discrepancy - Transfer Case to Transmission Transfer Adapter (2 Viewers)

[Gerrha]

I have come across a few discrepancies here and there in the FSM's, but this one I need to figure out. This regards the 6 bolts that clamp the transfer unit to the transmission transfer adapter. These are 12-mm x 1.25-mm pitch bolts and both parts are aluminum

The automatic transmission FSM for Step-38e of the Component Parts Installation section, states that these bolts should be torqued to 27 ft-lbf. This is the same torque value specified for this size of bolt pretty much throughout this FSM. However, the Repair Manual FSM for Step-9b of the Transfer Assembly Removal and Installation section, states that these 6 bolts should be torqued to 51 ft-lbf.

This is a big difference. I just tried to torque one of those bolts to 51 ft-lbf and I quit at about 40 ft-lbf because it just seemed too much and something was going to break.

Can someone enlighten me here?

 

[Malleus]

Both my copy of the service specifications for the transfer assembly, and the disassembly (steps 7, front extension housing and step 10, rear extensiosn housing) specify 27–lb·ft. Step 9b on my copy pertains to separating the shift fork no. 2 shaft and shift fork no. 2.

Can you post copies of the manuals you're using?

Which parts exactly are you trying to connect? There is no "transmission transfer adapter" in the service manual, by name.

 

[Malleus]

I can't find (at the moment) a specification, by name, for the transmission rear case adapter subassy to the transfer assy front case, which I assume are the two parts you're trying to connect:

 

[Malleus]

However, I do find these, in the transmission repair manual unit repair):

The nomenclature is lacking, but these are the same parts I referenced above.

 

[Malleus]

FWIW, this is the torque spec I used the last time I installed a transfer case, and it hasn't fallen off. Yet.

 

[Malleus]

OK, a little more sleuthing, because you piqued my curiosity. I frequently refer back to my copy of the 1994 service manual, because that's the latest one Toyota included torque values on the components diagrams, but, in this case, it's the same as the 3rd gen manuals – no transfer case to transmission torque values.

However, I compared my copy of the 2000 LX470 manual (which uses the same transmission and transfer, for all intents and purposes –yes, I know they aren't the same, but the differences don't matter here) to the 3rd gen 80 seies manual and voilà:

 

[Malleus]

If there's a section on removing the transfer from the transmission in the 80 series manuals, I can't find it. The transmission removal and installation section doesn't mention the transfer at all, and the transfer section assumes the transfer is on a bench. Odd.

It is in the 100 series manuals, though.

Now I have to really look at my notes to find out exactly what I did when I installed the transfer the last time...

 

[Malleus]

My notes say I used 51–lb·ft to connect the transmission and transfer. It's been awhile now, but I do remember those bolts were no fun. However, I made the mistake of installing the transfer onto the transmission afer I installed the transmssion. I won't be making that mistake ever again.

51–lb·ft is within the torque specification for those bolts, my copy of the generic torque table says max torque for that bolt is 53–lb·ft, although, I agree, that seems high for threads in aluminum of that size.

@SNLC or @Trollhole or @OGBeno do this enough that they would know, I'd think.

 

[Gerrha]

Yes, the parts in question are those you showed above. And I am using the same transmission FSM as the one you showed above with the 27 ft-lbf.

Shown below is the Repair Manual FSM with the 51 ft-lbf.

 

[Gerrha]

Would you recommend 27 ft-lbf?

 

[Malleus]

Exasperating. This is what the '94 (TIS version) service manual shows:

Here's the '95 version (again, from TIS; the '96 is similar):

and, for the sake of completeness, the '97 (TIS) manual:

No torque values, but at least they remembered to include the mounting bolts (in the very last year that it mattered). The TIS copy is differently paginated, but contains the same information:

I checked the LX450 manuals, too, because sometimes they include information that isn't in the Toyota manuals, but apparently they used the same tech writers.

I guess let us know if you strip the threads, or elect to stop at 40–lb·ft. It's hard to believe this slipped by so many people.

 

[Malleus]

Would you recommend 27 ft-lbf?

Personally, yes. And that's my engineering opinion.

My logic is that the transfer case elements use that torque value (and the same size bolts – I can't swear to the same grade), and those connections are at least as important as the transmission to transfer connection, which (correct me if I'm wrong about this) has two dowels in it.

Yes, I know there is an overhang situation in the transmission–to–transfer connection that doesn't exist in the front/rear case connection of the front/rear extension housings to front/rear case connections, but they also have rotating torque arms hanging off of them, which I'd think presents more of a potential failure point (dynamically) than the transfer case hanging off the transmission adapter.

I'd still like to hear from the guys who do this much more often than me.
@OGBeno @Trollhole @SNLC

 

[NeverFinis]

Official: 51 ft•lbf

Yes, my 1996 LX450 Manual doesn't show the torque values.

I just went outside and checked those bolts, at least the accessible ones.

I don't recall what I originally torqued them to, but they are definitely at, or near 51 ft-lbf now.

These are M12 bolts (M17 head), and can take a much higher torque than M10 (M14 head) bolts that attach the front and rear t-case housings.

 

[Gerrha]

Yes, there are two dowels there and they are beefy at 12-mm diameter.

 

[Malleus]

51–lb·ft it is. Noted (again) for posterity. You gotta love this site.

 

[Gerrha]

It seems 51 it will be. The odd thing is though; the adapter is bolted to the transmission by 8 bolts, on a smaller circle, torqued to 25 ft-lbf... And the transmission housing is bolted to the transmission via 6 bolts, 4 of which are at 25 ft-lbf and 2 at 42 ft-lbf...

 

[Godwin]

Timely thread, I'll be swapping out a t-case soon.