Pics Inside - T56 Magnum Do I Actually Need To Raise My Tunnel?

[csouth]

This is where the "DSE" stands as the are known become very helpful. You can put the weight of the car on all 4 wheels and work under the car without issue. I rarely use jackstands anymore. Build a set, you won't regret it.

Not my car, just posting for reference...

[AU Doc]

icemandrd19, thanks for the offer! I may take you up on that once I've had a chance to get back under the car and figure out exactly what's going on. I'll probably tighten everything down, and then set the car on the ground to get everything loaded properly and recheck angles. I'm still not sure what to think about all the clearance I have in my tunnel. I have new solid body mount bushings, and the car appears to be an original 40,000 mile car. So I don't know if it just hasn't settled as much as most cars, or I've got something out of whack somewhere and the car is going to sit down on the transmission after a few hundred miles.

Also, is brian finch still in business? I sent him an email when I saw your post, but haven't heard back.

ctcz28, thanks for the tips! You are correct that my engine/trans is at around 3*-3.5* down. From what I've read, that's the range to shoot for. Can you point me to where the 2.0* - 2.5* range is from? I've read a lot of conflicting info on this, so I'm trying to condense it down to what applies most to my setup.

Thanks again for all the help!

[AU Doc]

This is where the "DSE" stands as the are known become very helpful. You can put the weight of the car on all 4 wheels and work under the car without issue. I rarely use jackstands anymore. Build a set, you won't regret it.

Not my car, just posting for reference...

I've been thinking about doing something like this! I believe I'll build a set tomorrow

[csouth]

I've been thinking about doing something like this! I believe I'll build a set tomorrow

They were totally worth it for me, then you can take your time making sure you get the measurements correct.

[AU Doc]

Alright, I set the car down on the front suspension and things really didn't change much, if at all. I still have a ton of space between my transmission and tunnel. I had just about talked myself into cutting it out and moving it up an 1" for extra clearance, but I'm just not sure I see the point.

With my old school angle finder I'm getting around 3.5* engine trans down. The Tremec app shows around 4*-4.5*. I'm not sure which I trust more, so we'll go with 4* for now. This is measured off the front of the drivers head. I've also measured off the exposed part of the bell housing mounting flange which gives about the same measurement. I ran a string from the trans to the pinion and measure about 2* down to the pinion (it's tough to get an exact measurement off a string). The pinion unfortunately is also about 3* down. So it has to come up.

If I understand this correctly, I can shim my pinion up 3*. That would put my trans down 4*, my driveshaft at 2* down, and my pinion at 0*. That would give me a 2* angle at the trans and a 2* angle at the pinion relative to the driveshaft, which is a 0* working angle at rest. I would assume the pinion would move up under acceleration. However, I'm wondering if I should plan to shim the pinion about 4* to give myself some extra margin?

Any suggestions?

[parsonsj]

3.5* down is a lot. I try for 2*, and that means raising the tunnel, always. It also means for ideal driveline angles that your pinion points up to the transmission. (you're right, guys who want the pinion pointing down are often drag racers wanting more "dig").

[BonzoHansen]

Tremec app calculates operating angles, not outputshaft angle

[AU Doc]

The TREMEC app shows the angle while you are measuring. Once all three measurements are made it calculates the operating angles. At least that’s how it appears to work.

[AU Doc]

Thanks for the feedback. I decided to go ahead and raise the tunnel after I posted earlier. If nothing else I need the practice welding :-)

[ctcz28]

Maybe I missed in the earlier postings, but what are you using for the trans crossmember? Given that the crossmember will largely determine the angle your engine/trand combination makes, is there any adjustability with the crossmember or is it fixed? I used a crossmember from American Powertrain which has multiple positions.

[AU Doc]

I’m using the Holley mounts and crossmember. They are designed to give a 3*-3.5* engine/trans angle. So the angle I have is right in line with what they’re designed to do.

[AU Doc]

3.5* down is a lot. I try for 2*, and that means raising the tunnel, always. It also means for ideal driveline angles that your pinion points up to the transmission. (you're right, guys who want the pinion pointing down are often drag racers wanting more "dig").

Another question, this was mentioned before in the thread that the transmission angle should be closer to 2* down.

I sketched this out based on shimming my pinion to 1* up. Below is what I believe the scenarios are. I rounded to convenient numbers to make comparison easier.

With my current 4* down transmission angle, I would have u-joint angles of 2* (transmission) and 1* at the pinion. If I shim my transmission up to 2*, then I would have a 2* (transmission) and 3* at the pinion. The working angle would be the same in both cases, but the U-joint angle at the pinion would be worse with my transmission at 2*.

Can someone explain why I would want to shim my transmission to 2*?

[parsonsj]

A smaller angle (2* vs 4*) has several benefits, not all of which affect the rear pinion working angle. Benefits include: better ground clearance at the transmission, oil pan, and header collectors, easier exhaust routing, shorter shifter handle, better oil management in the pan, and better oil flow in the transmission.

Back to the pinion angle -- the working angles are also dependent on where the transmission output shaft is in relation to the pinion, height-wise. If the output shaft is the same height as the pinion, the driveline will be level and the working angles will only be the angles of the transmission and the pinion, which I think is what you've drawn. But if the driveline has to go up or down (because of a height difference between the transmission output and pinion), it can increase or decrease the working angles.

[AU Doc]

Thanks, John!

I went ahead and contacted The Driveshaft Shop and asked them what they'd like to see. I figure they'll probably be making the driveshaft, anyway. I'm going to shim the pinion to 2* and check my angles and then shim it to 3* and check again. I think the concern is my transmission and pinion are really close to being the same height. I don't want to end up with my driveshaft going uphill to my pinion.

That aside, surgery has begun on my tunnel. If I get some time this weekend, I may manage to get it welded up. The corners will be the tough part for me because I don't have any metal shaping tools. There shouldn't be much of that, though.

[AU Doc]

After spending a little time installing my console this weekend, it reminded me about this thread.

A quick recap, I did go ahead and raise my tunnel. However, at this point I can say for sure it was not necessary on my car. I do have a ton of space to work with between the transmission and the tunnel after raising it, but it also makes the console installation a little tighter than I would have liked. Particularly with respect to the shifter. If the tunnel was in the original position, it would put the console opening lower on the shifter handle, which would have been better.

I've run the car down the interstate several times at 70+ for short stretches, and I haven't felt any abnormal vibrations (knock on wood). So driveline angles seem to be ok. I would think with 4.11s at over 70 mph, it would be apparently quickly if things were out of whack.

In any case, I've got everything together, and it was a good learning experience. But this is at least one case where a 1969 Camaro could have run a T56 Magnum without tunnel surgery. I'm sure the Holley mounts and crossmember are the reason.

[c4racer2]

Anybody know if the Holley crossmember will also work with a traditional SBC and standard engine mounts? My application is a 2nd gen Camaro, but these mounts seem to work for both 1st and 2nd gen plus Novas.