Tranny mount bolts confusion (1 Viewer)

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So I ordered the bell housing bolt kit from SOR for my Landcruiser (1969). Excited, as I had been waiting 3 months to finish everything clutch-wise to mount the transmission finally, yet I tried the bottom bolt holes and they didn't fit. The top bell housing/tranny bolts are 19mm and fine thread. However, and this is where my brain starts to melt, the bottom bolts that we threw in there (were old engine mount bolts) don't have enough clearance for a socket once they get down to the head and are almost seated. I tightened them as much as I could but there is still 1/4 to go for them to be tight. So obviously there's a different bolt head for that bolt? I need some guidance, please.
The bottom bolt holes appear to be 17mm and coarse thread. I can't find the schematic and correct bolts apparently.
thanks for any help in advance, and Happy Thanksgiving!!

IMG-4188.jpeg
 

John McVicker

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I believe your best/easiest solution will be to actually use JIS bolts with the proper head. Try your local Toyota dealer. Maybe have the thread pitch & length needed & be sure they supply the actual JIS bolt.

Not gonna find JIS at Napa etc.
 

Skreddy

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If I remember right, don’t the bottom ones go in from the clutch side and thread into the trans?
 

John McVicker

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Definitely try to get the JIS bolts….BUT…you could also stack a bunch of washers of the proper size that allows the head of the bolt to protrude & be able to get proper torque. If you do this, use locktight.
 
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If I remember right, don’t the bottom ones go in from the clutch side and thread into the trans?
This is how it works with the 3 speed bellhousing to SM420 in my truck. I assume it's how it works with the toyota trans too.
 

middlecalf

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My Toyota 3-spd housing and tranny has the lower bolts enter from the clutch side. Not a great assembly pic but from the ‘65 parts book, check out orientation of bolt AQ vs. bolt AS, also size and length difference.
8E051BB7-C85E-4B93-8E70-67BE30526688.png

C836813B-A536-4B96-BA45-79738103EBDA.png
 
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John McVicker

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^^^
Good thought. Don’t know for a fact, but check it out.
 

73FJ40

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My Toyota 3-spd housing and tranny has the lower bolts enter from the clutch side. Not a great assembly pic but from the ‘65 parts book, check out orientation of bolt AQ vs. bolt AS, also size and length difference.
View attachment 3177120
View attachment 3177110
Bolt AS is M8 x 1.25 and holds the bearing retainer/nose cone in place. All four transmission to bell housing bolts are M13 x 1.5.

You are correct, however, the top two bolts screw into the bell housing, the bottom two screw into the transmission from inside the bell housing: (click to enlarge the following picture and you can see the assembled transmission to the bell housing with the bolt head protruding on top and the tip of the lower bolt protruding from the ear of the transmission housing)
1669345704958.jpeg


@Honeycutt should doublecheck where the threads are for his lower bolts. They should be in the transmission ears, and the bolts thread into the ears from inside the bell housing.

It appears from his picture his bolts embossed "5" are correct. It's not clear that there is a lock washer under it though.

Note that the bolt 91112-51340 appears to be still available from Toyota, $4.45 list, as well as the heavy duty split washer, 94512-01300, $1.38 list.

1669346103912.png
 
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Awesome info y'all! Ok, @73FJ40 I have the proper bolts on top (by the info gained in this thread), however, not sure if the same bolts are supposed to be used on the bottom to go through the bell housing from the inside to thread into the tranny. If that is the case, I'm all screwed up. I was able to get a 17mm bolt with course threads to screw into the tranny from the back on the driver's side, and then I try it on the passenger side and it's stripped!!
Now what am I going to do with that?:meh:

IMG-4201.jpeg
 
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And there is a lock washer on the top 2 bolts. Bottom two bolt holes have threads in the ears, passenger side seems stripped.
 

John McVicker

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@Honeycutt what I would do is determine the correct size & thread pitch of the bolt you just put in & then clean up the messed up hole with a proper sized tap. Most likely will be fine.

To accomplish this you must be careful, but it is not difficult.
 
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I wouldn't do that. If the threads are in the least fouled, replace them with a Timesert, Keensert or Helicoil. You do not want these bolts coming out, or even loosening. You cannot reliably "fix" a thread in cast steel (or reliably in any other cast metal, for that matter). Don't take shortcuts with your transmission; if you do you take the chance that you'll need a case, at the least. You've done all the rest of the work right, why screw it up now?

FWIW, All the JIS metric threads are coarse, by default. When the ISO standard (from the DIN, and from which JIS was developed), a deliberate decision was made to deviate from the fine/coarse series sets that characterized the Swiss and British (and following them, SAE) standards. Originally, the fine threads were intended for either very small diameters or adjustment designs. The coarse series was intended for general use. Over time, that idea was lost to the fog of history, and designs were developed for which the thread series wasn't optimal.

The geniuses who developed ISO, being the fascists they were, and wanting to control every aspect of life, decided they would "outlaw" fine threads and save all those unwashed masses of morons from themselves. Then the more enlightened German PhDs observed that coarse threads couldn't be used for very small diameteres and adjsutment designs, and so ISO put the fine thread series back in.

When Jimmy Carter decreed his empire would be metric, the government here decided to adopt every metric size, just in case we needed them for something in the future. That's why you can find odd size US metric fastener sizes just about everywhere, for which there is no international standard use.
 

73FJ40

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Awesome info y'all! Ok, @73FJ40 I have the proper bolts on top (by the info gained in this thread), however, not sure if the same bolts are supposed to be used on the bottom to go through the bell housing from the inside to thread into the tranny. If that is the case, I'm all screwed up. I was able to get a 17mm bolt with course threads to screw into the tranny from the back on the driver's side, and then I try it on the passenger side and it's stripped!!
Now what am I going to do with that?:meh:

View attachment 3177554

All four bolts are the same, 13mm diameter, 1.5mm thread pitch, 40mm length.

I don't know the history of disassembly, or why you needed to buy new bolts from SOR. In any case you need to understand the following:

Bolts are measured by their shaft diameter, not the size of the wrench that fits on the hex head. This must be fully understood when it comes to Toyota Land Cruisers, since they use 'special' bolts for fasteners. JIS bolt heads are not the same as other Metric bolt heads.

For instance 8mm diameter have JIS head of 12mm, (metric is 13mm);
10mm JIS, 14mm head;
12mm JIS, 17mm;
13mm JIS, 19mm.

So, if you're using a Toyota JIS bolt with a 17mm head, it's actually a 12mm diameter bolt. It could be it seems like the 12mm bolt is threading into the hole, but it really shouldn't.

Clean up the threads in the transmission ears, to see if the threads are there. If so, CONFIRM THE THREAD SIZES ON YOUR NEW BOLT (should be 1.5mm) and then get a plug tap to clean up the threads. A 13mm x 1.5 tap is not easy to come by, you may have to resort to Ebay and a tap from "international" sources.

If the threads really are stripped, you will need a plan B. Cross that bridge when you come to it.
 

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