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4th bolt between engine and trans?

rdomeck

Well-known member
Joined
Jun 1, 2011
Messages
620
Location
Indianapolis, In.
I installed a transmission last night and I noticed that the 4th bolt below the starter wasn't there. This is the hole that has the dowel pin in it from the engine. The engine block had a 10mm threaded hole in it while the trans had a 8mm threaded hole. I ended up drilling out the engine block for a threw bolt and drilling and tapping the transmission to accept a 10mm bolt. All 4 of the transmission that I have had this same set up! What do you guys do here? I supposed I could have installed a 8mm bolt, but since the rest of them are 10mm I really felt that one should be too!
 

thedsmguy

Well-known member
Joined
Mar 20, 2009
Messages
1,785
Location
Vancouver Washington
You are supposed to use a 12mm head bolt about 2.5" long and the factory bolt has a bit of a collar to the shaft but a normal 12mm works if you have to. Without this the pressure from the clutch tends to open up the gap from motor/trans and wears the clutch funny etc.
 

DynastyLCD

Well-known member
Joined
May 12, 2006
Messages
761
Location
Harwinton, CT
Quoting rdomeck:
I installed a transmission last night and I noticed that the 4th bolt below the starter wasn't there. This is the hole that has the dowel pin in it from the engine. The engine block had a 10mm threaded hole in it while the trans had a 8mm threaded hole. I ended up drilling out the engine block for a threw bolt and drilling and tapping the transmission to accept a 10mm bolt. All 4 of the transmission that I have had this same set up! What do you guys do here? I supposed I could have installed a 8mm bolt, but since the rest of them are 10mm I really felt that one should be too!



hmmm... this sounds like a pretty good idea. seems like every other transmission i get my hands on has these threads stripped out. how well did it work out? any clearance issues?

i agree that a wimpy little 8mm bolt really isn't sufficient for the job its put to. to put it in perspective, i did a clutch job for a friends civic, and that was a 1.6 i think? all trans bolts were 12mm. i found that very interesting. however, i haven't heard of people breaking transmission to block bolts.... besides when they forget the dowel pins.
 

rdomeck

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Joined
Jun 1, 2011
Messages
620
Location
Indianapolis, In.
Seemed to work just fine. Everything bolted up and I drove the car home tonight!
 

pauleyman

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Joined
Feb 27, 2011
Messages
91
Location
Oklahoma City, OK
There was no reason you needed to do that. The factory bolt is smaller and fits through the block. I have no idea why that hole is threaded. Likely it used in another car. All the AWD are like this.
 

rdomeck

Well-known member
Joined
Jun 1, 2011
Messages
620
Location
Indianapolis, In.
The reason was, I never had that bolt and wasn't sure what it looked like. I'm not sure if it was the cause, but one of the other three bolt was gone. So I only had two bolt's holding my transmission in!
 

grocery_getter

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Joined
Jun 20, 2004
Messages
1,225
Location
Kent - industrial suburbs of Seattle, WA
The bolt is a smaller 8mm size compared to the other 3 which are at 10 mm size. However, the 10 mm bolts are only a grade 7 bolt while the smaller 8mm is a grade 10 bolt. That 8mm blind hole bottom out into the tranny. I've come across some tranny where people put too long of an 8mm bolt and it punch thru the thin wall into the tranny. Pay attention to installation depth and bolt length.
 
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