LS3/4L60E swap and drivetrain angles?

[Clever Idiot]

Hey all! Been a while.

 

I'm looking at doing the big swap, and I like to plan everything down to the bolt as much as I can before getting into it. When I'm short on money, planning and dreaming is free

 

So I've read that in swapping in an LS engine with a 4L60E, one of the hurdles is getting the motor mounts and transmission mounts to be correct not just for clearance but to maintain the factory drivetrain angle. Apparently if the angle's wrong, bad things happen at highway speeds and/or to U-joints? 

 

I'm planning on these UMI Performance motor mounts unless someone has a better recommendation or a bad story about them.

 

1) Will I be ok moving the stock transmission crossmember back like I've seen others do or do I need to do something fancier? I plan on this being fully capable of highway speeds and road trips (including A/C and cruise). Not just a cruise to Dairy Queen every couple weeks.

 

2) How do I measure drivetrain angle and ensure that I'm good to go?

 

Thanks!

[Sam (Bones)]

Just Google it, there is tons and tons of info on it

[GatorDog72]

If the driveline angle does not match pinion angle, you will get a vibration from the U-joints. Get an angle checker like this one to check the angles of the front and rear u joints. If it's too far off, you may have to get adjustable rear suspension links to dial in the pinion angle. 

[Boots]

I bought one from a welding store... magnetic on both edges,,your harbour freight or stores like it will have it

[Clever Idiot]

Thanks, all. I did get adjustable rears, just in case I needed them in the future. Glad I did!

[andrewb70]

I am new here, because I like first get Monte Carlos (hopefully my next project), but I have done numerous LS swaps, most recently a 1967 Cougar and before that, my 1970 GTO. The best swap system for LS swaps right now is being made by Holley. They have engineered the mounts to place the engine as low as possible, which is accomplished by using their 302-2 oil pan. On a Monte the pan may not be needed because of the way that the engine sits on the front crossmember. 

 

I really like the Holley mounts because they use the factory 4th gen F-body engine mounts and combine that with custom brackets that bolt to the front crossmember. They also offer two positions for the engine and matching transmission crossmember for various transmission options. 

 

When I did my GTO swap, none of these parts were available and I was forced to use generic adapter plates and OEM frame stands. I had vibration issues at highway speed. The driveline alignment problems also get worse if the rear of the car is lowered (my GTO lowered 2-3" in the rear). The driveline alignment issues cannon be fixed with adjustable rear control arms because the issue is not getting the angles equal and opposite. The issue is that the u-joint operating angles get to be too big (anything over 3 degrees will cause vibrations at highway speeds). I ultimately fixed my vibration issues by using a driveshaft that uses a CV (think like a FWD axle) joint in the front.

 

Hope this helps.

 

Andrew