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Fractured Lower Engine Block Tab - Can It Be Welded?

abikepeddler

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Aug 11, 2016
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34
Location
San Diego, CA
I have been having shifting issues with our 91' GVR4.. after some investigating I discover we have a cracked bell housing. I tore the transmission out of the car and discovered not only is the bell housing cracked but the lower tab on the engine block that transmission bolts to has sheared off! (This is the one bolt on the engine to transmission interface that bolts in from the engine side) Motor has 45k on a fresh rebuild and outside of a 16g turbo and intake is pretty much stock. Do you think that this very important broken tab can be welded on successfully? It would suck to have to toss this motor simply because of the unfortunate breakage of this tab and I do not want to scrap a nice, rust free, original paint VR-4 over something like this.

Note: I did a search on the forum for any reference to others who may have faced this same issue to no avail..

Here are some pictures...








 

GSTwithPSI

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Jan 1, 2012
Messages
3,437
Location
SoCal
The only real way to fix it is to have the ear welded back on, or replace the block. The dowels are critical to ensuring the transmission is properly aligned with the engine block. The shifting issues you've been experiencing are a perfect example of how important that alignment is.

A temp fix like the ones linked below could be implemented, but not recommended for a long term solution IMO.

click
click


I saw a pretty nice fix on the FB groups IIRC, but can't seem to locate it...
 

iceman69510

Turn Right Racing
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Michigan
I took this same cruise. As it is cast iron, it't tough to do properly. I had mine welded by a welder I worked with, certified for Nuclear plant welding. It lasted about 2-3 years before it broke on me again in I-275 traffic in Detroit. /ubbthreads/images/graemlins/mad.gif I am not sure if there is anything else I could have or should have done differently to ensure a longer life. I know it was put together properly with all the dowels, etc.

I also didn't recognize at first that I was having shifting issues because of this and it did get worse before it stranded me. It was winter and I thought I was having clutch hydraulic system problems as it got more difficult to engage gears.

When I had a chance I replaced the block. Maybe it could have been fixed again, but didn't need the headache.
 

Gtpdz

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Mar 12, 2015
Messages
140
Location
Gig Harbor, WA
Seems like a common issue around this bolt mounts? I had the bolt snapped in the bell housing when some other trans bolt shake loose, eventually lead to shift problem. It started as noise that I thought was throwout bearing. But after fix this and bolt the transmission down tight again, all the clutch issue went away. I guess that's why Mitsubishi changed the trans bolt pattern for the 7 bolts?
 

Nebraska

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Apr 9, 2015
Messages
134
Location
Lincoln, NE
Cast is very difficult to weld correctly for durability, and a few may turn down the job offer but speaking from experience I can tell you it can be done and you can trust it when done right. I had a guy come to my house and do it with the block in the car. He used some methods I haven't seen before, like welding and putting a bunch of sand around the affected area...

Mine started when I'd push in the clutch and hear a clicking sound. Eventually I couldn't switch gears. What a mind boggler that was...
Good luck! You're not out of luck yet.

Oh and the flywheel chewed up my t case pretty good!
 
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iceman69510

Turn Right Racing
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Cast really needs preheating to weld properly. The sand was probably to slow heat transfer from the area.
 

abikepeddler

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Aug 11, 2016
Messages
34
Location
San Diego, CA
Thank you to everyone for the input. I appreciate the tips as to how to do this properly and will research Cast Iron Welding further before attempting a fix. I do quite a bit of welding and just bought a new Millermatic 215 kickass welder which should be able to handle the job. I think the trick to doing this properly may also include some additional gusseting to the welded area, something Mitsubishi probably should have already included in the orig block casting. That tab is not exactly overbuilt IMO. I am thinking that it will be easiest to weld by removing the clutch and flywheel and gain maximum access to the area. I also need to vent the crankcase because there is the risk of ignition of flammable crankcase gas which has been known to blow out oil pans. Still this will be a first for me welding a cast-iron block so wish me luck. I will try to update this post with some pictures... No making fun of my welds! Ha ha..
 

abikepeddler

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Joined
Aug 11, 2016
Messages
34
Location
San Diego, CA

Update:

So I was able to successfully weld on the broken cast iron transmission mount and am ready to put everything back together and get #1607 back on the road. I followed some GVR4 members suggestion and also welded on a steel plate that I drilled out to allow a longer bolt to become the new main source of support for the transmission in this area because I agree with others that the repaired cast iron engine/transmission tab is not likely to hold. Soooo I have a question...

The original cast iron engine block tab that I welded back on also has a hollow dowel that the transmission guides onto when installed. I thought that the transmission bolt just passed through this hollow dowel and threaded into the transmission bell housing but I discovered that the dowel itself is also threaded. Is this normal? Does the bolt that holds the transmission to the engine block thread through both the hollow dowel and then thread into the transmission bell housing? That seems really weird. It must be this way because I did not modify the tab or dowel in any way but figured I must ask prior to proceeding...

Picture attached is prior to welding and is for reference.


 

FlyingEagle

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Mar 5, 2005
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THE Ottawa
Your dowel is appearing to have a "threaded" interior from the bolt mashing about once loose/tab broke.

The dowel is simply there as an all around support and it is not threaded by design, it is smooth inside and out, when you start with a new part. Be sure to have a new dowel (any trans shop/machine shop/good parts place should have them) and be sure it is a friction fit that requires a "press" to work. Essentially any C clamp will work with appropriately flat contact surfaces that won't round the dowel or cause harm on either piece you push on.

Double threaded parts, is a rare thing, and you don't see it for a reason, well quite a few actually. So, hope that helps answer your question before the final push.
 

abikepeddler

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Aug 11, 2016
Messages
34
Location
San Diego, CA
This makes sense except for it feels perfectly and purposely machined (threaded) when I install the bolt. But I know what you are saying... Many bad things could happen with two threaded parts being bolted together especially in a high load environment such as this engine to transmission interface. So I'm really confused by this and am wondering if it would be best to just drill out the seemingly threaded dowel so the bolt can do it's job of marrying the two surfaces. Hmmm...


Quoting FlyingEagle:
Your dowel is appearing to have a "threaded" interior from the bolt mashing about once loose/tab broke.

The dowel is simply there as an all around support and it is not threaded by design, it is smooth inside and out, when you start with a new part. Be sure to have a new dowel (any trans shop/machine shop/good parts place should have them) and be sure it is a friction fit that requires a "press" to work. Essentially any C clamp will work with appropriately flat contact surfaces that won't round the dowel or cause harm on either piece you push on.

Double threaded parts, is a rare thing, and you don't see it for a reason, well quite a few actually. So, hope that helps answer your question before the final push.

 

transparentdsm

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Jul 27, 2011
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Klamath Falls, Or
Quoting abikepeddler:
It is the same size and pitch as the other 3 trans bolts only longer.




this is why the tab broke, that is not supposed to be a large bolt, someone jammed it in there and thought it was right, but it never actually attached to the transmission, but whenit was ran through the dowel it tighted the dowel to the transmission.

these are the 6 bolts that attach the transmission.



the second to last bolt on the right is the bolt that should have been in the tab that broke.
 

fuel

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Feb 23, 2009
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Toronto, ON, Canada
^^ the main difference between the other bigger bolts is that it has a 12mm head rather than 14mm of the other bellhousing bolts - excluding the smaller bolts that hold on the inspection cover of course.
 

transparentdsm

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thats what i noticed in the first picture with the bolt still in is the head looked like a 14mm.

the head isn't the only difference though the size of the entire bolt is smaller. its a 10mm x 1.5 and the other bolts are 12mm x 1.5
 
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abikepeddler

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Aug 11, 2016
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San Diego, CA
This is EXCELLENT information! Thank you! I do have the correct bolt and am going to test fit an extra bell housing I have to make sure everything lines up correctly and that I have the correct bolts going to the correct places. There is a good chance that the large 14mm bolt was never in this location prior and that I accidentally mixed it up with the 12mm one that is correct for that location during disassembly. (I was really organized in noting what bolts went where but spilled a tray of labeled bolts so... You get the picture...) I do find it odd that the larger 14mm bolt also threads into the all 3 of the bell housing I have on hand. The 12mm never seemed to so I just assumed the 14mm was correct. I'll retry the 12mm again and update. Thanks for the guidance.
 
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abikepeddler

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Aug 11, 2016
Messages
34
Location
San Diego, CA
Well crap. I figured out what is going on. The correct 12mm blot threads into my original (cracked) bell housing just fine with nice clean threads etc... The other two bell housings (including the one I just installed on the transmission) will not accept the correct 12mm as the threaded area is to large as though it has been drilled out prior or damaged from some previous incorrect installation/use.

Pictures "A" and "B" show the incorrect 14m bolt threading right into the not so great looking treads while picture "C" is of my original bell housing. You can see the nice clean threads which accepts the 12mm bolt perfectly.

Sooo... either I... ??? Try and find yet ANOTHER bell housing with good threads or... tap the existing and try and clean up the threads enough to use a larger 14mm bolt or... buy a brand new $2300 transmission or...

I am getting tired of locating replacement used bell housings only to find that have been knackered to sh*t. This is getting expensive.









Quoting transparentdsm:



these are the 6 bolts that attach the transmission.



the second to last bolt on the right is the bolt that should have been in the tab that broke.




 

mitsuturbo

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Jun 2, 2008
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Near Seattle, Washington
Welding the block won't hold. Been there. Done that.
Take a chunk of plate steel, i think i used 1/8". Weld it to outside of the motor mount bracket so it hangs down enough you can drill a hole thru it that will perfectly line up with the transmission. Use the original busted piece and some washers to fill the gap. If you need to drill it out to fit a larger bolt, then so be it. The block chunk can be drilled, it's already broken. Tap the bellhousing and use a m10x1.25 bolt of appropriate length and strength if you can't use the m8x1.25 threads anymore.
 

diambo4life

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Jul 7, 2013
Messages
265
Location
Edmond, OK. USA.
Quoting abikepeddler:
Well crap. I figured out what is going on. The correct 12mm blot threads into my original (cracked) bell housing just fine with nice clean threads etc... The other two bell housings (including the one I just installed on the transmission) will not accept the correct 12mm as the threaded area is to large as though it has been drilled out prior or damaged from some previous incorrect installation/use.

Pictures "A" and "B" show the incorrect 14m bolt threading right into the not so great looking treads while picture "C" is of my original bell housing. You can see the nice clean threads which accepts the 12mm bolt perfectly.

Sooo... either I... ??? Try and find yet ANOTHER bell housing with good threads or... tap the existing and try and clean up the threads enough to use a larger 14mm bolt or... buy a brand new $2300 transmission or...

I am getting tired of locating replacement used bell housings only to find that have been knackered to sh*t. This is getting expensive.









Quoting transparentdsm:



these are the 6 bolts that attach the transmission.



the second to last bolt on the right is the bolt that should have been in the tab that broke.









I am just seeing this. I drill out and tap all my transmissions to accept a bigger bolt on the block to bell housing side. The bolt through that hole should be the same size as the other 3 bigger transmission bolts. This is a very common mod. Could have just sent me a PM and would have told you this. Sorry about that!
 
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