diehrd

I just put in a 4L80e (1980 corvette) and it looks like the angle is going to be difficult to get right.

Any tips tricks and suggestions would be great , pics of how your drive shaft runs down tunnel would be cool to

Solid LT1

There isn't a real critical driveline angle when you going from one stationary part (trans) the another (IRS) you do need an offset to prevent the needle bearings in the U-joints from stalling and failing to circulate around the U-joint truninon. The factory offset is around 3/4" as I recall.

doorgunner

Rookie questions: Are you referring to 3/4" vertical offset....or 3/4" horizontal offset.....or a combination of both?

Postal123

I thought 3-5 degrees of offset was considered ideal with our set-ups? It's been a while, but I do remember adjusting for an angular offset. Was this bad info?

Garys 68

What's the engine/trans angle?
When I measured mine, the engine, differential, and driveshaft were all close to 0 degrees.

diehrd

I have a 4l80e with a 24 inch drive shaft ,, and i will measure it later or in the morning. I am heading out today to get an angle finder tool ..

But the trans has a decent down angle more then a few degrees .. And even when pushed into the tunnel all the way it is still pointing down so looking at it the drive shaft looks like it is up at rear pinion and down at trans if you can visualize that ..

cagotzmann

Interesting to see the out come. I am putting a T56 Magnum in my 78 and have similar items to look at. The original TH350 looked very level with the engine and diff. actual about .4 degrees. During test fitting , the longer transmission ( shorter drive shaft ) doesn't fit high enough in the tunnel to make a straight line. I am waiting for my crossmember to see where it will sit.

What crossmember are you using ?

doorgunner

I'm going into the garage now to check the angles.....be back in a few minutes.

doorgunner

I'm not using a Machinist's level which is accurate to within 1/10 the thickness of a human hair/I'm using my Home Depot Angle Finder...LOL.

It is showing less than 1 degree at the TH400 pan/along the driveshaft to the differential.

I think the main thing that matters is that the "face" of the universal joint at the transmission is somewhat parallel with the "face" of the universal joint at the differential which would require a "little" shimming of the components.

74modified

The simple explanation is that when a U-joint is at an angle, it is moving faster on one side than the other as it spins. Because you have two - if one joint has a larger angle than the other, it can cause harmonic vibration. So if both U-joints have the same angle, it cancels out the vibration. It doesn't have to be an exact match, but they should be pretty close. When you change transmissions, cross members, ect (from stock) the angles could get wacky. Sometimes you have to shim or adjust the mounts - trans or diff, to get the angles close. There have been a number of threads here covering the subject.

gve

I used the Tremec drive line angle app its free and you use your smart phone as a degree tool. I had a vibration at higher speeds with my tremec and after using this app if all the numbers are within the allowed limits the 3 numbers will be green if any are red they are out of the limits. Also make sure the drive line from front to back is straight. I put my car up on a lift and ran a string from the center of the engine to the center of the rear end I then laid on a creeper and was able to see that I needed to slide the transmission to one side to get everything inline.

Here is an article on how to use it.

http://www.hotrod.com/how-to/additio...le-finder-app/

Postal123

Try shimming the trans mount til your carb base is level...then check you driveshaft angle at the tail shaft and pinion. Forgot this tip in my first post...it worked well for me.

doorgunner

Thanks Members for all the info.....I'm sending it to my copier. I'll use it to check my driveline---it's not vibrating, but I would like to know how close it is to being "straight/correct angles".

lionelhutz

Lots of people don't realize it and many car driveshaft articles miss this fact, but besides the angles being opposite of each other, it will also work with both angles the same. For example, the typical article will only say that if the transmission is down 3* that the pinion should be up 3*. But having both the transmission down 3* and the pinion down 3* would also work.

Patro46

Frankly, I'm impressed as hell you the thing to fit. I went with a 4L60e, and it was TIGHT! Mine is a 74, so your tranny tunnel might be different

diehrd

As far as fit it is basically a TH 400 with over drive in it making it a little longer then a TH 400 . Also it is the strongest unit you can put into a car and I prefer that dependability vs a 700r4 or its cousin the 4l60e..

Today I will check and set angles, both left and right and up and down hopefully it all comes together.

doorgunner

No one really wants to modify the body of an original car......BUT....I had to add some "extra clearance to the tunnel in certain places" to fit the automatic the way it needed to be in my '34 street truck.

cardo0

Yea that 4L80E takes up some room - nice choice though. Ive always read to keep the lines parallel - steep angles OK. U will find plenty to read on this forum here if u search for driveline angles. Frequent topic here.

Good luck diehard. Hope to read bout driving your new big inch sbc soon.

havesometo

cardo0

Heres a great video of driveshaft angles and corrections: http://www.macsmotorcitygarage.com/2...e-and-phasing/.

It was copied from a thread by ignatz: https://www.corvetteforum.com/forums...aft-angle.html.

Maybe ignatz will chime in, hes really knowlegable having corrected his issues.

Hope this helps.