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Thread: rear motor mount brkt modification pics

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2008-01-06 00:47:12
rear motor mount brkt modification pics
Well as most of you know about my stupid bolts on the back motor mount bracket breaking chunks out of my tranny due to wheel hop. Well i made a little custom modification that would take the support off the tranny where it is most prone to cracking and breaking and put it on the block itself on the two thicker 17mm bolts. Here are the pics of what i have done so far but the bracket is still going to need more support because it started to bend the middle section at the top of the bracket where there is no cross support. So more modifications will come later to it to make it solid.

Here is what happens when you wheel hop at the track. Weak cases indeed.

Here is what has been done to the bracket so far, more support will be put in the upper middle of the bracket where it started to bend. so for now i have the one bolt at the lower part of the bracket going into the tranny that is fully tightened down. once its done that bolt will come out where its the most prone to crack the case and dump your gear oil out all over the ground.

Here are pics of it bolted up into position. good fitment, had to grind a little bit off the block where it indents in near the bolts but nothing major.

Thats it so far, i will keep it updated on how it looks.
2008-01-06 06:23:09
here's what I did to help wheel hop. it's great and really doesnt resonate through the cabin like i thought it would.

solid motor mount
2008-01-06 06:42:22
i have prothane mounts all the way around but i made the mistake of making my first pass without lowering the tire pressure and it hopped. but i did it to see what my trap speed would be on normal tire pressures to get an idea of what the car is making power wise. oh well.
2008-01-06 06:55:51
Originally Posted by Octave
here's what I did to help wheel hop. it's great and really doesnt resonate through the cabin like i thought it would.

solid motor mount

is that full of lead??? if so its going to be freaking heavy, and will eventually deform try some epoxy
2008-01-06 20:43:14
yeap. you say going as in like future tense. lol once i get another welder this is the option for now. works great... IF it deforms cause lead is soft it's an easy fix. solid front and back mounts. prothane side mounts and the control arm inserts. the big square ones and no wheel hop at the track on 225/50r15 BFG's with 2.0 60 ft. the next run I snapped the axle from accidently dumping the clutch to quick trying to spin debree off the tires before lining up at the stage lights.

edit: sorry worded it wrong before
2008-01-06 20:52:08
yeah lead has no rebound its probably already deformed here's what you need
2008-01-06 21:08:42
The tranny cracking as it did is generally the cause of people putting in the wrong bolts in there.

I have dragged race many an SER and never had this problem.

Solid engine mounts ( Nismo, prothane ) get rid of 60% of wheel hop, Solid rubber bushings for the control arms about 20% and a frount sway bar will completly get rid of wheel hop.

I will admit that welding on that pc for the second 17mm bolt will cause less stress on the back of the tranny so good job on that.
2008-01-06 21:25:10
Originally Posted by waltg
yeah lead has no rebound its probably already deformed here's what you need

Rebound? I wanted solid I figured that ment no rebound. If it deforms im going with steel. The mount only has 2 weeks worth of driving on it. I figured the prothane and solid rubber mounts were as good as you could get and not let too many vibrations carry through the cabin but it's not bothered me at all just going solid metal.

This is what happened when I wheel hopped. 17" wheels with 40 series side wall.

2008-01-06 22:48:10
ouch, but it looks like it also cracked at the bottom bolt that goes through bracket. thats where ive seen all the cracks happen, its a bad point on our trannies to have a high stress motor mount. all the stress and vibration when wheel hop occurs hits that back mount. its not a good design to prevent this kind of thing from happening. Yeah we should all have the right stuff to preven wheel hop but it still tends to happen, all i need is the control arm bushings and front sway bar bushings which are not that expensive just havent gotten them yet. and a set of traction bars would be best but that doesnt always happen,

from what ive seen on other cars. most rear mounts are bolted to the block for the most part. there are still some that do put it generally in the same location. but the ones that are bolted to the block itself you really never hear about cracked cases. if you look at it its always the portion that sticks past the block where the back motor mount bracket bolts to is where all the cracks happen. i dont think ive ever seen it crack down the middle of the case where it would be bolted to the block. Its just a high stress point.

Now Andreas i get what your saying about the wrong bolts but i made sure the proper bolts were in each spot. if you look at it the chunks that are missing are pretty big and where the threads are you can tell the bolts were a ways into the bolt holes. Now whether or not they might have worked loose is another story being i didnt check that before i ran. That could be a cause. but from previous experience the cracks do always happen at the bracket point not any other spot on the case.
2008-01-06 23:29:26
wheel hope is a bitch ! run a solid front dog bone and the rest prothanes and have the front end suspension set on soft when launching like that.

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