Do I need a raised driveline tunnel for aftermarket suspension/stance?

[72Xbody]

This question could technically fit into a couple of different categories, but it's pretty straightforward. For those of you with lower ride heights, and possibly modern suspension components and power/drivetrains, was it necessary for you to raise your driveshaft tunnel to get proper driveline angles? For example:

My car is a 72 Nova. I will be running a Speedtech torque arm suspension, and most likely bolt-on components for my factory subframe. I will also be running a T56, so I expect to modify the trans tunnel at bare minimum. Car is receiving mini tubs as we speak.



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To achieve a stance similar to the one pictured above (speedtech-built Nova), do you believe it would be absolutely necessary to raise the entire tunnel? (with something akin to the speedtech extreme tunnel cover?) As I mentioned, I am currently installing mini tubs -- the car is just a shell at the moment and I'd like to knock out all of the metal fab work before moving on. i.e. -- if I need to raise the tunnel, now is the time. Any help, opinions, experience, knowledge etc is appreciated!

[dhutton]

I don’t know about Novas but Holley claims no tunnel mods needed with their mounts, accessory drive, headers and trans mount on first gen Camaros.

The Speedtech tunnel mod is easily done if needed.

Don

[72Xbody]

Hey Don,

Thank you for your reply. I went ahead and looked into those mounts and such, but I forgot to mention that I am running a small block with the T56. I'm kind of figuring it couldn't hurt to just go ahead and install the raised tunnel. Have you happened to install one before? My main concern is cutting/reconstructing the front floor brace/crossmember.

Buddy

[65 drop top]

If it were me, I’d just install the raised tunnel now. Much easier to do it now, and no one has ever regretted having a little extra room under the car. Just my 2 cents…

[dhutton]

Hey Don,

Thank you for your reply. I went ahead and looked into those mounts and such, but I forgot to mention that I am running a small block with the T56. I'm kind of figuring it couldn't hurt to just go ahead and install the raised tunnel. Have you happened to install one before? My main concern is cutting/reconstructing the front floor brace/crossmember.

Buddy

Not sure about the Nova but there is no floor brace on first gen Camaros that has to be cut.

Don

[mbheinz]

I have a 70 Nova with a TCI torque arm, sbc, T56, mini tubbed and ridetech front suspension on the factory subframe. There was no need to do anything to the tunnel on my car. Here is a pic of the car a few years ago with a ridetech 4 link in the rear and 255 mm wide tires in the front. I now have the torque arm and 275 mm wide front tires but the stance is the same. If I were to lower it anymore in the front I would have front tire rub issues and the front cross member, oil pan and bell housing would be too low for my comfort. As it is I shaved about an inch off the bottom of the bell housing for clearance, run 2 degrees negative camber in the front, notched the subframe in 4 places and
clearanced the front inner fenders to clear everything. I autocross the car plus I think running the widest tires you can on all 4 corners really looks good.

[Pedigry]

It can affect your engine angle as well. The lower the car, the more engine angle you need to get the trans in the tunnel. The problem is that when you get above 3 degree's, your pinion angle will also be around 3 degrees and it can create vibrations that are tough to get rid of. I am fighting one right now and I am at 3.5 degrees. Cut the tunnel, then get your engine angle down to 2 degrees or less, you will also not have to run into positive angle driveshaft, which is a whole other set of problems.

[72Xbody]

mbheinz, thank you for that. That's the info I'm looking for, for sure. What kind of engine/driveline/pinion angles are you getting with that setup? Did you modify your trans tunnel at all in the front for the T56? Thanks

[72Xbody]

Pedigry, I've considered just doing that as well. I figure it couldn't hurt, but we also just had a new one piece floor installed. I don't care to cut it, but if it wasn't necessary at all I'd leave it alone. Doesn't the engine angle stay relatively unchanged when lowering the car? I've never built one this way, so I very well could be wrong, but wouldn't the location of the engine and trans relative to the body stay the same? I would imagine you'd mainly run into problems with at the rear end.

[Z06vet]

I can't comment on the nova body floor, but as far as ride height and acceptable working angles go- this is the biggest issue I have dealt with: The lower the ride height, the higher the pinion on the rear end sits in relation to the trans tailshaft. Real problems occur when it sits higher than the trans yoke. The driveshaft slopes upward to the rear end. No amount of pinion adjustment will eliminate all the vibration. It just creates odd angles that can't be compensated for. Raising the trans tailshaft so that is higher than the rear end solves 95% of vibration issues, along with setting the pinion to allow acceptable working angles between the trans, driveshaft, and rear end. A raised tunnel allows more room to raise the trans tailshaft. I wish I could add more to help, but I haven't done a nova, nor run a sbc/t56 setup. I can say that with the LSx and T56, using stock frames & holley clamshell mounts (they lower the engine in the frame) I have not had to raise the tunnel on camaro & firebird applications.

[Pedigry]

What Z06 said. The pinion angle is an issue on lowered vehicles, especially when the pinion angle gets "upside down", then chasing rear end diff vibrations is really tough. The trans size will ultimately dictate how flat you can get the engine angle. T56 is a big tranny. I have a C6 in my car and a gear vendors, which is pushed as far up the tunnel as I can get it and it's not enough. I'm stuck at 3.5 degrees for now. If I wasn't going to put a TKX trans in it and get rid of the C6 and gear vendors I would be cutting the tunnel out. Some aren't bothered by vibrations but it completely pulls me out of the enjoyment of the car so I will chase it till it's gone. Either way, I'm just trying to help you with the setup. Once everything is in the car your options are limited and the idea of pulling everything out and resetting the drive angle is overwhelming. If you test fit everything and come up with a engine/pinion of more than 3 degrees, my humble opinion would be to cut the tunnel. Best of luck and let us know what you decide.

[Pedigry]

I have a 70 Nova with a TCI torque arm, sbc, T56, mini tubbed and ridetech front suspension on the factory subframe. There was no need to do anything to the tunnel on my car. Here is a pic of the car a few years ago with a ridetech 4 link in the rear and 255 mm wide tires in the front. I now have the torque arm and 275 mm wide front tires but the stance is the same. If I were to lower it anymore in the front I would have front tire rub issues and the front cross member, oil pan and bell housing would be too low for my comfort. As it is I shaved about an inch off the bottom of the bell housing for clearance, run 2 degrees negative camber in the front, notched the subframe in 4 places and
clearanced the front inner fenders to clear everything. I autocross the car plus I think running the widest tires you can on all 4 corners really looks good.

Beautiful car. Stance is great. Do you happen to know what your engine and pinion angle are?

[mbheinz]

I just checked my engine and it's angled down toward the rear of the car at a 4.7 degree angle. With the torque arm under the driveshaft I can't get an angle of the driveshaft right now. We moved to East Tennessee 3 months ago and I'm still setting up my shop area. I have one more autocross to finish out the year then the car goes under the knife for a new front clip and a bunch of other upgrades. Once its in the shop and up off the ground I can get better measurements which I'll need for setting up the new angles. I didn't set it up as it is now but the only vibrations I've had were after flat spotting tires. So at this point I'm not sure on the need to cut the trans tunnel or not. My thoughts would be to just do it so it doesn't come into play later. You guys are suggesting a lot of good information!

There are so many hurdles to getting a 3rd gen Nova low. Right now the 3 inch exhaust is the lowest part on the car,. Hooker made a new design header a few years ago that fits tighter to the bottom of the car. The lowest point on the header is at 4 inches and the vband clamp at the back of the header is at 3.25 inches of ground clearance. They are 1 3/4 primaries and work well. I have a Dart based 427 as well. There was some header interference with the ridetech Truturn and I needed to make a few adjustments to the tie rods to get it all to work together. Now I have a small amount of bump steer I didn't have before. The new front clip and front mounted rack and pinion should fix that issue. Hopefully the headers will clear the steering between the column and the rack. We'll see.

Another issue is the depth of the oil pan. That's one thing I looked at on the OP's picture of the car in the welcome section of the forum. I went with a Kevco 1091RR. It's 7 1/2 inches deep and sits just above the stock front crossmember and cleared the ridetech Truturn. The oil pan in the picture looks good. As I said before I had to trim off the bottom of the bell housing flange and plate. My first autocross with this set up I bottomed out and grooved the parking lot. Not good!

I hope I can get more info for the OP before he actually needs it and look forward to possibly autocrossing with him!

[72Xbody]

I just checked my engine and it's angled down toward the rear of the car at a 4.7 degree angle. With the torque arm under the driveshaft I can't get an angle of the driveshaft right now. We moved to East Tennessee 3 months ago and I'm still setting up my shop area. I have one more autocross to finish out the year then the car goes under the knife for a new front clip and a bunch of other upgrades. Once its in the shop and up off the ground I can get better measurements which I'll need for setting up the new angles. I didn't set it up as it is now but the only vibrations I've had were after flat spotting tires. So at this point I'm not sure on the need to cut the trans tunnel or not. My thoughts would be to just do it so it doesn't come into play later. You guys are suggesting a lot of good information!

There are so many hurdles to getting a 3rd gen Nova low. Right now the 3 inch exhaust is the lowest part on the car,. Hooker made a new design header a few years ago that fits tighter to the bottom of the car. The lowest point on the header is at 4 inches and the vband clamp at the back of the header is at 3.25 inches of ground clearance. They are 1 3/4 primaries and work well. I have a Dart based 427 as well. There was some header interference with the ridetech Truturn and I needed to make a few adjustments to the tie rods to get it all to work together. Now I have a small amount of bump steer I didn't have before. The new front clip and front mounted rack and pinion should fix that issue. Hopefully the headers will clear the steering between the column and the rack. We'll see.

Another issue is the depth of the oil pan. That's one thing I looked at on the OP's picture of the car in the welcome section of the forum. I went with a Kevco 1091RR. It's 7 1/2 inches deep and sits just above the stock front crossmember and cleared the ridetech Truturn. The oil pan in the picture looks good. As I said before I had to trim off the bottom of the bell housing flange and plate. My first autocross with this set up I bottomed out and grooved the parking lot. Not good!

I hope I can get more info for the OP before he actually needs it and look forward to possibly autocrossing with him!

I really appreciate the info. What part of East TN are you in now? I am in East TN as well! You've done a lot of modifications that I've been looking to do myself, heck if you're somewhat close by I'd love to check your car out! I'm pecking away at mine as fast as possible, one part at a time...just finished one side on the mini-tub and starting the other side in about a week. Likely doing DSE subframe connectors next, or the trans tunnel if I can get that figured out. I may give Speedtech a call on Monday and see what they think about it as well. You can cut the trans tunnel by itself to get the tailshaft farter up into the tunnel, or raise the entirety of the driveline tunnel. That could be overkill for my goals, but then again, I doubt it could hurt in the end.

[mbheinz]

I really appreciate the info. What part of East TN are you in now? I am in East TN as well! You've done a lot of modifications that I've been looking to do myself, heck if you're somewhat close by I'd love to check your car out! I'm pecking away at mine as fast as possible, one part at a time...just finished one side on the mini-tub and starting the other side in about a week. Likely doing DSE subframe connectors next, or the trans tunnel if I can get that figured out. I may give Speedtech a call on Monday and see what they think about it as well. You can cut the trans tunnel by itself to get the tailshaft farter up into the tunnel, or raise the entirety of the driveline tunnel. That could be overkill for my goals, but then again, I doubt it could hurt in the end.

I'm in Kingsport. You are welcome to check out the car and see what I've done to it, right and wrong, lol.

[72Xbody]

Well dang. I’m in Kingsport too lol. I still can’t direct message on here, but shoot me a text. 423-276-9132. I’ll be a bit tied up for the next week or so, Rod Run is coming up this weekend so I’ve gotta get my other car ready, but I’d definitely like to swing by next week if you’re around

[Pedigry]

My car is low as well. Around 4" from the ground for the headers. But I live in Florida where the roads are really good. If I lived up North it would never work but I don't have any trouble with driveway lips or normal driving, haven't hit anything yet (knock on wood). I think the clearance issue is really dependant upon where you live and how good/bad the roads are.

4.7 degrees seems really high to me. The driveline working angles should be less than 3 degrees. But that's working angle, not simple engine angle or pinion angle. Try and get the angle of the driveshaft and add or subtract the number off the engine/trans angle to get your actual working angle. Tremec has a great little app that can give you the working angles and see if they are in spec, that should at least give you a start.

Best of luck and let us know how it turns out.

[72Xbody]

After a lot of thought and some phone calls with speedtech, I decided to just raise the entire driveline tunnel. They make a pre-fabbed tunnel that makes it a lot easier. For the money, I figure it's worth it for the sake of clearance insurance later down the road. I'll update this thread and my project thread once I receive it and get it installed.

[Pedigry]

Wise choice. At least this way you do it once, you do it right, you don't have to do it over. You will also be able to get the driveline angle right.

[Cdog]

As of last night I'm dealing with this after installing the Lt1/T56 into my 69 Camaro with Art Morrison frame. Trying to decide which way to go. The Speedtech extreme tunnel looks like the best fit for me. Has anyone blended the tail portion and extended it to make a smoother transition into the drive shaft tunnel? I'm not running a center console and would like to blend the tail portion to look close to factory.