Bellhousing to Transmission Bolts (2 Viewers)

[RWBeringer4x4]

Hey all,

Pretty basic question but unfortunately my truck was too much of a mess to show a definitive answer...

I'm getting ready to install my Downey V8 conversion bellhousing. I spoke with Jim and he mentioned I'd need to go to 1/2" Allen head screws to mount to his bellhousing. It looks like the thread pitch is about a 16.

What I need to know is - do the four bolts that hold the transmission to the bellhousing need washers or lock washers?

Correct me if I'm wrong - The Downey bellhousing is threaded through about 1" bosses, so I don't think I will need to add nuts inside the housing (which would also make disassembly tricky).

Just trying to get a ballpark bolt length and want to factor in any washers, nuts, etc.

Unfortunately when this transmission came out, it has 3 M12x1.25 bolts, one with a lock washer, plus a 1/2in, coarse thread bolt with a washer and lock washer, PLUS through-bolted to a nut inside the bellhousing, so I have no idea what to think, haha

 

[4Cruisers]

The OEM bolts (91619-61240) for mating the 4-speed to the bellhousing (on the FJ60s at least) have a lock washer only. The same bolt, but 5mm shorter, is shown for the mid-'70s FJ40 (91619-61235).

 

[RWBeringer4x4]

Thanks - that solves the lock washer question. I'm assuming no nuts on the inside of the bellhousing - they're just held together by the threaded bosses?

 

[4Cruisers]

That's how they were designed, no nuts inside the bellhousing.

 

[pb4ugo]

1st I must say, I'm not familiar w/ Downeys' bellhousing.

1/2" bolts come in either 1/2-13 or 1/2-20. Socket head cap screws(SHCS) or allen bolts typically use high collar lock washers. A standard lock washer will probably work, but have a larger OD than the head on a SCHS.

 

[RWBeringer4x4]

1/2" bolts come in either 1/2-13 or 1/2-20. Socket head cap screws(SHCS) or allen bolt typically use a high collar lock washers.

well - after trying a ton of thread chasers, miscellaneous bolts, etc. to try and figure this out, all I can conclude is that they were marginally larger than 7/16-14, and M12x1.75, but wouldn't take 1/2" in either 1/2-13 or 1/2-20. I just ended up tapping to 1/2-13.

 

[SuperDuperCruizer]

Found this thread in my search for information about the bolt that attaches the transmission to the bell housing. I realize th OP was referencing a V8 bell housing but it thought I’d point out another option.

I just converted an FJ62 transfer case to a manual setup for the H55F. This left me with a few bolts I no longer need. They appear to be about the right length and the correct thread pitch. Just have 3 of them though. I don’t see why they wouldn’t work for the job. I’m bolting a 5-speed to a cast iron 3B bell housing btw. Now, let me see if I can find a fourth to match.

 

[4Cruisers]

Found this thread in my search for information about the bolt that attaches the transmission to the bell housing. I realize th OP was referencing a V8 bell housing but it thought I’d point out another option.

I just converted an FJ62 transfer case to a manual setup for the H55F. This left me with a few bolts I no longer need. They appear to be about the right length and the correct thread pitch. Just have 3 of them though. I don’t see why they wouldn’t work for the job. I’m bolting a 5-speed to a cast iron 3B bell housing btw. Now, let me see if I can find a fourth to match.

View attachment 1545038

Just finished this myself, I may have the bolt you're looking for - I'll take alook in a few minutes. BTW, for mating the transfer case to the transmission I used three long bolts from a one-piece transfer case to mid- to late '70s 4-speed transmission, along with appropriate lock washers.

 

[SuperDuperCruizer]

Thanks for the offer @4Cruisers I found the 4th bolt soaking in some solvent.

 

[4Cruisers]

Messages crossed paths - my Internet's been down for a few hours.

You should have four of those bolts left over after your conversion. I just pulled mine out of the garage, they're 45mm long and look just like the one you pictured above. I also have four M12X1.25 bolts 45mm long with captive lock washers and four M12X1.25 bolts 42mm long with no captive washers. Let me know what you find and we can go from there.

 

[bikersmurf]

If the Downey Belhousing you're getting is like mine you could easily put nuts on the inside before the engine is in place.

I mounted it to the engine with standard hex bolts... but it is a major PITA to get them done up and undone. I'd agree that Allen head bolts would be much easier.

 

[Mid TN]

What's the length of the M12x1.25" bolts? Is a flat washer and lock washer what is normally used?
Anyone have the exact factory specs.?

 

[4Cruisers]

What's the length of the M12x1.25" bolts? Is a flat washer and lock washer what is normally used?
Anyone have the exact factory specs.?

As far as I've been able to find out, the transmission to bellhousing bolts for FJ40s and FJ60s with split transfer cases are M12X1.25, 40mm long (from under the head to the end of the bolt), 5T (strength), with captive lock washers and flat washers.

 

[Mid TN]

4Cruisers-Thank you so much, I was going to get 50mm long. It just dawned on me, I could go pull one out of my parts 60, though no guarantee it was correct!