Engine/Transmission Tilt

[Hemi8]

What is the preferred/recommended/allowed tilt of the engine/trans? I set my pinion angle (up) to match my trans shaft angle (down) -2 degrees. The engine/trans tilt is 5.6 degrees down, the car is already built. If I need to raise the trans it would require major surgery ie; cutting out the trans tunnel, something I don't want to do.
Mike
86 GN, stage II, TH400

[Z06vet]

That is way too much downward angle in my experience. -3 degrees or less is much more acceptable. I had to raise the tunnel after the fact on one of my very first builds. I wouldn't say it was major, but it was a needed inconvenience.

[MuscleRodz]

Should be around 3* down engine/trans, roughly 2-3* down pinion for leafs, 0* down for 4 link will put you in the ball park.

[jlcustomz]

Sticking larger trans in tunnel than will fit & pointing trans down to compensate is a common mistake that leads to driveshaft vibration issues.

[another69]

If possible, you could lower the engine mounts to decrease the driveline angle.

[minendrews68]

Should be around 3* down engine/trans, roughly 2-3* down pinion for leafs, 0* down for 4 link will put you in the ball park.

OK here goes one of those dreaded ignorant questions. When measuring the degree of descent be it 3* or what ever, from where do you measure? I mean what do you attache a inclinometer to? On the rear end it's the machined area the cover bolts to (chevrolet) I think.

[Z06vet]

Face of the harmonic balancer, oil pan rail, or trans output shaft (yoke removed)

[minendrews68]

Face of the harmonic balancer, oil pan rail, or trans output shaft (yoke removed)

Well that makes sense. Thanks for the answer!

[BMR Sales]

also check your angle finder to see if it's measuring correctly. There are a number of Apps for phones instead of using a HF piece

[sccacuda]

The operating angles of the driveshaft, relative to the reared and trans is what is important. Simply changing the angle of one part without the proper working angle will not fix an issue, and could actually make it worse. Here is an easy calculator to help: https://spicerparts.com/calculators/driveline-operating-angle-calculator

Most U-joints should have 3* or less operation angle, 3* being max and not ideal.

[minendrews68]

The operating angles of the driveshaft, relative to the reared and trans is what is important. Simply changing the angle of one part without the proper working angle will not fix an issue, and could actually make it worse. Here is an easy calculator to help: https://spicerparts.com/calculators/driveline-operating-angle-calculator

Most U-joints should have 3* or less operation angle, 3* being max and not ideal.

That's some pretty good information. Clears up a lot in my feeble brain.

[JEFFTATE]

The engine/transmission centerline angle and the pinion shaft centerline angle should be parallel ( or as close as possible ). The driveshaft angle should be around 3 degrees different from the other two.
https://www.driveshaftshop.com/angle-calibration

[Hemi8]

I may have enough room to put a spacer between the trans & mount to kick it up to 3 degrees, I think the exhaust will need adjustment afterwards. There are plenty of G-body cars running TH400 trans so I don't think tunnel surgery is needed. Thanks for the advise.

Mike

[Hemi8]

After much measuring following the Spicer calculator I found that yes, trans tunnel has to be cut. I think because I strayed from the stock ride height (lowered coil over suspension) and the poly stage II motor mounts I have run into this situation, can't really fight it, just have to deal with it. The driveshaft is almost straight as it sits, so the u-joints will eat themselves in short order. Luckily Hurst sells a trans tunnel kit for installing a T56 trans. in a G-body, the fun part this weekend was pulling out the interior and then removing the Dynamat from the trans tunnel (dry ice), that is some real sticky stuff.
Before:
Engine/trans 4.75 degrees down
Pinion 2 degrees up (this is adjustable)
Driveshaft 0.56 degrees down
After: we'll see

[andrewb70]

After much measuring following the Spicer calculator I found that yes, trans tunnel has to be cut. I think because I strayed from the stock ride height (lowered coil over suspension) and the poly stage II motor mounts I have run into this situation, can't really fight it, just have to deal with it. The driveshaft is almost straight as it sits, so the u-joints will eat themselves in short order. Luckily Hurst sells a trans tunnel kit for installing a T56 trans. in a G-body, the fun part this weekend was pulling out the interior and then removing the Dynamat from the trans tunnel (dry ice), that is some real sticky stuff.
Before:
Engine/trans 4.75 degrees down
Pinion 2 degrees up (this is adjustable)
Driveshaft 0.56 degrees down
After: we'll see

Another option is to use a driveshaft with CV joints. I have a single CV shaft in my GTO and a dual CV shaft in my Cougar. They are made by The Driveshaft Shop.

Andrew

[Hemi8]

Cut tunnel, raised the trans by 1.1" using a pile of shims and now have 2.90 degrees downward tilt. This caused my 4" driveshaft to hit the tunnel so I went with a 3.5" MW chromemoly shaft. Now I need to weld-in the Hurst trans tunnel (2 piece) after I fill in the stick shift hole.
Now I'm looking for a high quality shifter. I have the Kwik Shift shifter from Precision but do not like it. I have a manual forward VB and with the Kwik Shift I can push it straight into neutral from 2nd gear, not cool. I think the Kwik shift is only good with CO2 shifted drag car setups. I am eyeing the TCI Outlaw shifter, looks like it has hard stop gates 1-2 and 2-3 for foolproof shifting.
166296166297166298166299

[c4racer2]

Tremec makes a nice app for the iphone for finding angles. I have a canton oil pan with a flat bottom - so took my measurements off that.
I ended up about 2.5* without using any shims - motor mounts are lowered .75" and speedtech T56 crossmember for 2nd gen camaro.
Headers and exhaust work perfectly at that angle too btw - off the shelf stuff there, not custom made.