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Thanks for the response. I was planing on using a right angle drill attachment to try to drill the hole. I guess it would still be tricky to get it straight. Yes the transmission is still in the car. Dang this just sucks! I don't know what I am going to do.
 

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I will remove the mount tomorrow to see how much room I actually have to see if I can drill the hole straight and use the helicoil.
 

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Discussion Starter #24 (Edited)
Thanks for the response. I was planing on using a right angle drill attachment to try to drill the hole. I guess it would still be tricky to get it straight. Yes the transmission is still in the car. Dang this just sucks! I don't know what I am going to do.
I agree, it really sucks! I don't think you have enough room to even use a right angle drill, and it be VERY hard to drill it straight even if you did have enough room. You REALLY don't want to mess up that hole. I have installed two helicoils in the mount holes on a 94 Toyota Celica transmission, and even with the transmission out of the car, it was hard to drill that hole straight with a hand held drill. On the first hole, I ended up with some expansion of outside end of the hole just because I couldn't hold the drill straight enough without some movement. Fortunately, I could set the helicoil a little deeper, and the mount bolt was long enough to fully engage. If I recall correctly, for the second hole, I started with smaller drill bits, and then worked my way up to the proper sized bit. I was able to keep it straighter that way as the hole was better able to guide the drill bit and allowed me to hold the drill more lightly. Maybe you can do it this way with a right angle drill attachment, but I think it is a long shot.

I predict you are going to remove the transmission and do a proper job. There are threads here on how to best do it. On the bright side, you would get an opportunity to inspect your clutch (just trying to find something positive here).
 

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I agree, it really sucks! I don't think you have enough room to even use a right angle drill, and it be VERY hard to drill it straight even if you did have enough room. You REALLY don't want to mess up that hole. I have installed two helicoils in the mount holes on a 94 Toyota Celica transmission, and even with the transmission out of the car, it was hard to drill that hole straight with a hand held drill. On the first hole, I ended up with some expansion of outside end of the hole just because I could hold the drill straight enough without some movement. Fortunately, I could set the helicoil a little deeper, and the mount bolt was long enough to fully engage. If I recall correctly, for the second hole, I started with smaller drill bits, and then worked my way up to the proper sized bit. I was able to keep it straighter that way as the hole was better able to guide the drill bit and allowed me to hold the drill more lightly. Maybe you can do it this way with a right angle drill attachment, but I think it is a long shot.

I predict you are going to remove the transmission and do a proper job. There are threads here on how to best do it. On the bright side, you would get an opportunity to inspect your clutch (just trying to find something positive here).
Stepping up the bit size was one idea I had. I have a friend who is really good with a drill who is going to help out if I decide to try it. Thanks for thinking on the positive side if I have to remove the tranny.
 

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depending on how badly the threads are stripped, you might be able to chase it with a thread restorer kit from your local parts shop. Something like this:

.

On my DD, I stripped not one, but three, engine mount holes on the aluminum tranny housing - all three were restored with such a kit.

Hopefully, the first few threads are ok and it'll go in straight by hand, then use a socket or wrench to rotate the cutter the rest of the way. Keep a capful of oil handy and don't be shy with it. Patience helps too. Go a full turn or so, back it out, re-oil, and repeat.

EDIT: If you go the rental route, make sure it has the right tap. The kits I saw had both coarse (1.5) & fine (1.25) taps. I can't remember if they are labeled with the thread pitch or not. I think I needed 12mm fine for my DD, so the kit should have a 10x1.25 one for you.
 

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Thanks for the suggestion. I guess it would not hurt to try because if it does not work I would be drilling the hole out larger for the helicoil any ways.
 

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Discussion Starter #28
I looked through the 2000 Celica GTS manual for the proper torque of the engine mount brackets to the engine/transmission, and I found 3 of the 4 mounts. The manual doesn't mention a front mount for the 2000 Celica, which seems really odd. All cars I have worked on have the usual 4 mounts.

Note that the engine in the Elise is on the same side of the car as it is on the Celica, so right, left, front and rear references between the two are the same.

The torque of these bracket bolts into the aluminum of the engine block and transmission housing is more limited by the aluminum threads rather than the bolt itself.

Here is what I found:
Rear Engine Mount bracket to transmission housing: 47 ft.lbs
Right side engine mount bracket to engine: 36 ft.lbs.
Left side engine mount bracket to transmission housing: 44 ft.lbs
Front: can't find it. If the bracket bolts are the same on front and rear (diameter, thread pitch, and length of thread engagement), I would expect that the torque of the front would be the same as the rear. However, I just don't know if they are the same (I never took off the rear bracket to tranny bolts). If someone has the Corolla or Matrix manuals with the 2ZZ-GE engine and C60 or C64 manual transmission, please look this up. I had estimated 40.5 ft.lbs. in my original post, based on the bolt specification, but it would be 47 ft.lbs. if it was the same as the rear.

Big bolt through center of insualtor:
These are for the 2000 Celica GTS manual transmission, and I don't know if Lotus used the same bolts:
Rear mount bolt through center of insulator: 64 ft.lbs. (I had estimate 69 based on the bolt type)
Left hand mount bolt through center of insulator: 59 ft.lbs.
 

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Discussion Starter #29
I just verified that the same bolts are used for both the front and rear engine mount bracket to transmission housing. In the attached picture (from the Lotus parts manual), part 23 is used for both front and rear.

Given that the Toyota Celica, Corolla and Matrix factory manuals all specify 47 ft.lbs. for the rear bracket-housing bolts on the manual C60 transmission (which is the same housing as the C64 - just some internal gearing differences) with the 2ZZ-GE engine, I think we can confidently say that the front bolts should also be 47 ft.lbs.
 

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I finally ended up fixing my issue. The hole was completely stripped of all threads. The hole was 1/64 smaller then the required size for the helicoil kit for a 3/8" bolt. So I took my time and slowly taped the hole. Removing the tap and cleaning the shavings every 1/2 turn. Took forever but it worked. 3/8 is only .5 mm different from the original 10mm bolt so I should be good to go. I will check this mount with my regular maintenance from now on.
 

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ChrisH - Thanks for starting this thread - the info is very useful.

For reference, I'm working on a 2011 Elise SC. I just installed Sector 111's TrackMount2 pair front and back. Several people have commented on needing a special tool to get to the front mount bolts that go into the transmission. Instead of the low-profile socket or swivel head wrench, I was able to use a regular socket on a short extension. The total length of the tool is 4-1/8". Here's a photo of how I used the tool to get to both bolts:



I had to push an oil cooler line slightly out of the way to get the ratchet in place. That's a Snap-On socket, Craftsman extension, and a Proto ratchet :)

I forgot to measure the rear mount bolt thread pitch, but I did catch this before I put it back in:

...

2) Forward lower mount
...

2b) big center bolt through mount
Class: 8.8 I think. (The only marking on the bolt head was 11. I don't know what that means, but Lotus generally doesn't use the higher class bolts.)
Diameter: M10 (10 mm)
Pitch: 1.25 I think (measured it, but lost my note. This my best recollection.)
Plated (not sure with what)
Recommended torque for this specification: 40.5 foot-lbs
1.25 mm pitch is correct. The bolt is plated with yellow cadmium.

Glen
 

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I was upgrading the lower engine mounts. Here are the bolts I examined:
1) Rear lower mount:
1a) mount to frame, rearmost pair (with nuts)
Class: 8.8 (says so on the bolt head)
Diameter: M10 (10 mm)
Pitch: 1.5 mm (thread spacing, which is how metric bolts are specified)
Plated (looks like zinc)
Recommended torque for this specification: 38.25 foot-lbs

1b) mount to frame, forward pair (bolts into frame)
Class: 8.8 I think (not listed on the bolt)
Diameter: M8 (8 mm) I think. I forgot to measure it before installing, but it was definitly a size smaller than the other pair of bolts (1a).
Pitch: 1.25 I think (again, forgot to measure, but the threads didn't seem as fine as a 1.00 pitch)
Plated (looks like zinc)
Recommended torque for this specification: 18.75 foot-lbs
I just did the rear motor mount in my Elise. The four bolts that mount to the frame are the identical size. All seem to be M10x1.5.
Only the heads are different. The forward pair have undersized 13mm heads. I confirmed this but threading the nuts from the rear pair to the bolts on the forward pair and they fit. I assume then that the specified torque value of 18.75 is incorrect and should be the 38.25 like the other pair?

Jose Soriano
 

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I just did the rear motor mount in my Elise. The four bolts that mount to the frame are the identical size. All seem to be M10x1.5.
Only the heads are different. The forward pair have undersized 13mm heads. I confirmed this but threading the nuts from the rear pair to the bolts on the forward pair and they fit. I assume then that the specified torque value of 18.75 is incorrect and should be the 38.25 like the other pair?

Jose Soriano
In theory, but in practice those bolts don't do anything really so just make them snug enough that they dont back out. Otherwise those threads in the frame aren't the best and you can get the bolt stuck or strip the hole.

I don't even use mine and I track the car heavily.
 

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I recently replaced my transmission and torqued the rear large center bolt to 69 ftlbs and it loosened big time on first track weekend. I seems like it should have a lock washer. I did not use any thread lock.
 

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I recently replaced my transmission and torqued the rear large center bolt to 69 ftlbs and it loosened big time on first track weekend. I seems like it should have a lock washer. I did not use any thread lock.
Wow. I'm surprised at that. I've never had that happen. Is the problem solved now?
 
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