Editing Engine and transmission mounts

Here you are driving down the street enjoying the sound of the car and the tunes coming from the dash when you suddenly realize that you are passing the street that you want. You jab on the brake but are not fast enough and you slide past it. In your haste, you jam the stick into reverse and hit the gas. [['''BANG''']] All of a sudden you have strange screeching and clattering  noises coming from under the hood. What the hell! You shut it down and get out to open the hood.

With the hood open, you start to look around the engine bay but there appears to be nothing wrong. You jump back in start it up and it idles fine. A couple of small pulses on the pedal assures you its OK. You pop it in to gear and step on the gas. You hear a big CLUNK and there's that clattering noise back again. You immediately shut it down again and all is quiet as you wonder aloud, "What the hell's that??". 

You pop the hood and have a better look around this time. You notice now that there is a chunk taken out of the rad shroud and the fan blade is scratched and bent slightly. The engine has a slight list to one side and the puddle of antifreeze that used to sit by the thermostat housing has now shifted towards the head. You go back in and hit the key but this time as the starter turns the engine over that strange noises are re-occurring over again and you shut it off. 

A few of the locals start moving towards your car and a passing motorist asks if you need help. You are now painfully aware that you are blocking the intersection and questions and no answers are echoing in the back of your head. A couple of the locals are looking under your hood and nodding amongst each other as you hear someone say, "Looks like a broken motor mount to me!". You instantly have visions of the engine falling out there on the street as you carefully open the door and get out of the car. As you meet at the front of the car, one gray haired gent says, "Yep, it looks the motor mount, Son." Many questions come to mind.


== What causes broken motor mounts ==

Motor mounts live in an environment of heat, oil and fuel leakage, and constant vibration and torque. They reside in close to 1000+ degrees of heat from the exhaust manifolds or headers and are subjected to deterioration by oil and fuel leakage from the valve cover gaskets and fuel lines. Most OEM motor mounts are made from compound rubber and steel frames. Many motor mounts will spend a couple hundred thousand miles and multi years before ending their life. The final result of their life will be 'shear', whereby the upper and lower units of the mount will be torn in two, usually caused by overtorquing the engine mounts much the same as the scenario above stated.


[[Image:Problem_-_cure.jpg‎]]


== Motor Mount Construction ==

Most OEM mounts are made of a steel frame which one side will bolt into the cast iron engine block and the other side will be clamped to the frame by way of a thru-bolt. The upper and lower mount frames will be sandwiched with a layer of rubber and cotton fiber reinforcement that is vulcanized and molded to the metal frames.

In most cases aftermarket motor mounts will have some sort of overlapping of the upper and lower frames to hold the units together in case of accidental separation.

[[Typical Aftermarket Motor Mount]][[Image:Energy_susp_motor_mount.jpg‎ ]]

[[Image:Chevy_24087_motor_mount.jpg‎ ]]


Early type Chevies offered two types of motor mounts, a short and wide and a tall and narrow.

[[Image:Early_style_GM_mount.jpg‎]]

Oldsmobile also offered short and tall models that could be mixed to offer a lower than normal mount or a taller than normal mount. Here is an idea of the rough measurements that you can get:

a) small block engine mounts with small block frame mounts - OK

b) big block engine mounts with big block frame mounts - OK

c) small block engine mounts with big block frame mounts - the engine will be 1-2" low

d) big block engine mounts with small block frame mounts - the engine will be 1-2" high

(IMAGE)



== Replacing Motor Mounts ==

Usually motor mounts do not require the engine to be removed from the vehicle, but in some cases additional clearances requires it. Besides lifting the engine up, the vehicle must also be raised to allow parts to be disconnected and connected. In some cases, rad shrouds, exhaust manifolds, fuel and water lines, linkages may have to be loosened or removed. There is odd times that engines have to be removed to do replacement mounts, but this is rare.

Always replace mounts in pairs. Even though the other looks good, you have the equipment available and spending the time now is better. Also look at replacing the rear trans mount, especially if they are OEM equipment. In some cases, mounts may come as a complete kit for your application.

[[Image:Eng_-_trans_mount_kit.jpg‎ ]]

1. Gather all equipment together to do the job. This includes engine lift, roller jacks, jack stands, drain pans, speciality tools, wood blocking and planks.

2. Find a level surface, block rear wheels and jack up the front of vehicle to a level which allows you a safe access under the vehicle. Block up the vehicle using jack stands under the frame.

3. Place engine lift at front. Remove air cleaners, fan shrouds, and battery cables. Loosen or remove exhaust pipes, water and fuel lines if necessary and drain them. Install lifting chain or lifting plate to engine block, do an initial lift to engine and then inspect.

4. Check for electrical wires, lines and hoses that are pulled. Check for clearance between engine and firewall, and transmission and floor pans. Check for rad to fan clearance. Check steering shaft to manifold clearance.

5. Continue raising engine to a suitable working and mount removal height. Remove thru-bolts from both mounts. Make engine stable using jack stands, wood blocking and planks. Wiggle engine around to simulate working on it. REMEMBER: YOUR FINGERS WILL BE IN CLOSE PROXIMITY TO THE FRAME AND OTHER APPARATUS.

6. Remove mounts from engine and frame. Compare old parts to new replacements. Inspect for any damage to engine and frame. Chase out the threads in the block with a bottoming tap and use new grade 8 bolts and washers of the appropriate size. Install new mounts. Apply lubrication to all bolt threads and tighten to specifications. Lower engine and align lower mounts, insert thru-bolts and tighten up hardware. Thru-bolts are usually a knurled grade 8 type for maximum shear resistance.

7. Continue lowering engine and reassemble parts and equipment as required. Lower vehicle to ground after final inspection.

Note: If replacing transmission mounts, raise transmission after loosening bolts and slide in new mounts,finger tighten bolts before lowering vehicle. Tighten and torque down bolts. Use a nut tab bolt or a force bolt to ensure that these bolts don't back out.