Lowering engine mouinting point
 

I am fabbing something for my TII, and in order for it to fit perfect, I would need to lower the engine a .250". Will this have any bad effects?

I will lower the engine by making a set of solid motor mounts that are .250" less in height. The only thing I could think of that it would effect is the angle of the driveshaft. But i am unsure if .250" is enough to cause any problems. It dosnt seem like much at all, but you never know. I'm sure the old stock rubber mounts have sagged a good bit in the last 20 years, maybe even further than .250"?

I could always put a few washers to make up for that .250" to lower the tranny also. But that dosnt change where the diff mounts. And I dont really want to shim all the diff/subframe mounts.

It will effect the drivetrain angle. Not sure if it will be enough to cause vibrations though. U-joints from what I've been told need to to with ~2.5* of each other to not vibrate. Welcome to my world, this 6-spd is still vibrating on me.

Also, you wouldn't need to lower the subframe, just the nose of the diff, or the raise the ass end of the rear. Shiming the subframe down won't change the angle of the pinion flange and that's what you would need to do.

What I would be more concerned about is the angle of the subframe lands and the bolt that needs to pass through it. Being much shorter, that .25" will have more of an impact on the mount angle than the d/s angle

It will effect the drivetrain angle. Not sure if it will be enough to cause vibrations though. U-joints from what I've been told need to to with ~2.5* of each other to not vibrate. Welcome to my world, this 6-spd is still vibrating on me.

Also, you wouldn't need to lower the subframe, just the nose of the diff, or the raise the ass end of the rear. Shiming the subframe down won't change the angle of the pinion flange and that's what you would need to do.

What I would be more concerned about is the angle of the subframe lands and the bolt that needs to pass through it. Being much shorter, that .25" will have more of an impact on the mount angle than the d/s angle

The reason why i think I can get away with it is because I'm pretty sure the 20 year old stock rubber mounts have to have enough sag already. So i don't think anything would even change much. But i can't be sure. TII driveshafts are getting harder and harder to come by, and i don't want to start ruining them just to lower the engine down a 1/4"...

What you're talking about is compression, not sagging. I don't think they've compressed that much.

Well i don't know for sure that they sag or compress, i'm kinda just guessing.

If you look at the mounts and see how much they have mushroomed out, it looks pretty bad on just about every set I have seen. Plus they are rubber and will compress with the weight of the engine.

I will try and meaure the stock mount complete height while on the car today. This should let me know how much difference my mounts will make.

I am already deciding against lowering the motor, but I am still making my own mounts. So I want to figure what height I should make them. I measured another aftermarket motor mount at 1.700". I would like to see how an old stock mount compares to that while installed.

The rubber is to reduce the vibration transmitted through the chasis. In effect it isolates the engine from the car allowing the engine to operate independent of vibrations on the car.

If lowering the engine is worthwhile you can easily get another drive shaft made and ensure the proper angle between the transmission and differential. The end issue (beyond angle) is how much of the fabrication you're willing to do to ensure proper angles.

I just finished making the motor mounts. I made them .250" shorter as i stated earlier. But i also made four .125" thick shims for them. One on top and one for the bottom of each mount. I will install the mounts without the shims, then try and meaure the driveshaft angle at the differential. If it is any more than 3 degrees, I will add the shims to correct it.

I guess the only real way to know is to try it and see for myself.

I'm gonna take a shot in the dark here and tell you that a little 3 degree angle on a driveshaft doesn't matter at all. That's my two cents anyways. Just look at a typical RWD vehicle with a live axle the driveshaft has to move up and down more than 3 degrees. I will admit I've never measured one before but it seems like common sense. I'm sure you'll be fine lowering the engine. The U-joints need a small amount of misalignment anyways to work properly.

Ill say this. If it was my car I'd do it without a second thought.

You could also compensate the transmission mount to accomodate the lowered engine mount to help restore the original pinion angle. Also when you say that most mounts have compressed over the 20yrs you also forget that most the driveshafts have given up by now also. I can't be conclusive that the mounts compressing are what caused this but i can sure bet it helped the u-joints go out.

With lowering the engine you may also want to check the clearence between the steering rack on the front of the oil pan.

Zack.

The problem is, and this is my exact problem, if I can't get the angles proper, I'm going to have yet another d/s made, not a typical u-joint but a double-cardon where each joint cancels itself out. That's the key from all the research that I've been doing. The angles need to be equal and opposite to cancel themselves out.

See the above post, by dropping the engine and not the tranny, you are increasing the angle of the d/s yoke, making more of an angle on that first u-joint. The rear angle, where the d/s meets the flangeis going to change as well, but in the opposite direction. There's also the offest angles that need to be dealt with as well and those almost require the removal of the tailshaft housing and a few plumb-bobs and a line drawn down the center of the car. I've planned all this out in my head and will actually be tackling it on Friday... I'll a bunch of pics of how I'm doing it, and let you know what my d/s guy says about the various angles. The bitch is really going to be keeping the tranny in it's mounted location, without the mount

When the suspendion drops like that, there's usually not much speed associated with it. There's a ton of information on lifted trucks and drivetrain vibes out there. My truck vibes EVER so slightly when I'm hard on the gas around 60ish in 4th, then it smooths out. Been planning on that SYE kit for 2 years now........for shame...

Very true Zach, but as I said earlier, it's the angle between the output shaft and the d/s as well as the angle OF the output shaft, and the angles of everything else.

HAAHAHA! You're totally right and COMPLETLEY forgot about that. That's some tightness in there especially if you're running a studded pan brace

But by just dropping the front, you will affectively be raising the rear at the same time( because of how the tranny crossmember is, it makes it a pivotal point) you could then decrease the overall height of the cylindrical tranny mounts to lower the tailshaft back donw to were it originally was. Hopefully without changing the pinion angle.

Then again. what was the whole purpose of lowering the engine? lol

Very true about the angle of the output shaft on the tranny, much better said than how I did, BUT, the pinion angle won't change unless you alter the mounts in the rear. What WILL change however is the angle that the rear u-joint sees. By lowering the engine, you raise the tranny (as you said) so you're creating more of an angle at the front u-joint. By doing this you're creating LESS of an angle at the pinion. The pinion is angled back 5* (I BELIEVE, need to more accurately measure) and by lowering the engine, you're raising the rear of the trans creating MORE angle in the front, LESS angle in the rear, you may get to a point where the offset is out of the range of the u-joints and shit will start to vibrate..... this is what concerns me.... this is what I am dealing with right now. The only difference is I am dealing with the offset (side to side angles - or so I believe) not the up and down angles that he's talking about. They all play a role... sadly

Right on, but when you lowering the front it's raising the rear. So then by lowering the rear tranny mount you would be bring it back down to were it originally was. Atleast it's works perfect like that in my head. Lol

Zack.

But by doing that you're lowering the d/s as well and increasing the angle between the d/s and the pinion. The pinion is angled back and offset from the center of the car as well. You could get to the point where the engine, tranny, and d/s are all perfectly level and the pinion is still at a 5* angle... that will vibrate.

That's very true. Didn't think about that. Like I said it all works perfectly in my head. Lol. What was the op original purpose of doing this?

I was going to make a slightly thicker top mount intercooler.

I'll just stick with what I have for now. I'm putting the mounts in as the correct height. I can always remove the shims later on to lower the engine...

Why not just modify the hood?

Because I have spare TII hoods just laying around?

lol... J/K. I actually do have a spare just sitting there.

lol this is zack, we still on for sat right?

How much thicker of a topmount are you going for? Why not just run a v-mount setup?