Correcting pinion and driveline angles by lowering transmission mount

[Smokinnjokin]

Friends,
I am working through driveability improvements with the car and need some opinions on correcting pinion angle. I have caltracs and a higher-than stock ride height on my '67 satellite, which of course has changed driveline angles. At rest with weight on the wheels, transmission is sitting 5 degrees nose down, driveshaft is 3 degrees nose up, and pinion is 1 degree nose down. U-joint angles are 8 front, 4 rear. Now the obvious fix is to toss a 3-4 degree shim pack on the rear axle to tip the pinion down further so I am almost parallel (cal-trac doesn't allow much movement of pinion, plus I don't drag race).
BUT... I am not crazy about the 8 degree u-joint angle. Would it not make more sense to get a shorter transmission mount and tip the transmission angle down closer to level, and bring it parallel to pinion that way? If I can lower the transmission 3-4 degrees, that would bring me parallel and also lower u-joint angle to a more reasonable 4-5degrees.
Follow-up question... does anyone make/sell a transmission mount that is shorter? I know they can be shimmed higher, but the design does not seem to allow for any modification to shorten it. How much shorter does it need to be for a 3-4 degree change in angle... There's a math problem there for sure.

 

[pnora]

I would be welding new axle perches on.

 

[BLK 68 R/T]

Agreed. Start playing with the transmission angle and you’ll likely end up with radiator fan to shroud clearance issues.

 

[beanhead]

The transmission is 5-deg NOSE down? Do you mean tailshaft down, or is it actually pointing down in the front? They almost always want to sit at at a tail-down angle somewhere between 0-3 degrees.
Firstly, ignore what the driveshaft is doing. What matters is getting the pinion to rotate up to parallel with the trans under load (which doesn't have to be 'racing' load, the pinion wants to climb the ring even driving normally). With the Caltracs you only need to adjust for 2-3 degrees of axle rotation.
"If it was me" I'd definitely be correcting the transmission angle first, especially if it is pointing tail-up.

 

[oldkimmer]

If it is already 5 degree’s down (at the rear) u need to raise it up. Forget about the drive shaft and it’s angles. U need the pinion 3 degree’s down from the tranny. Frankly I’ve never seen the tranny out that much. How are the motor mounts? Give us some more insight. Kim

 

[oldkimmer]

The transmission is 5-deg NOSE down? Do you mean tailshaft down, or is it actually pointing down in the front? They almost always want to sit at at a tail-down angle somewhere between 0-3 degrees.
Firstly, ignore what the driveshaft is doing. What matters is getting the pinion to rotate up to parallel with the trans under load (which doesn't have to be 'racing' load, the pinion wants to climb the ring even driving normally). With the Caltracs you only need to adjust for 2-3 degrees of axle rotation.
"If it was me" I'd definitely be correcting the transmission angle first, especially if it is pointing tail-up.

Then his motor is way too low.

 

[beanhead]

Okay I just read your OP again, and judging by the fact you're wanting to shorten the trans mount, it does seem you mean truly 'nose down'.
Do you have the correct mount in there? Or (thanks Kimmer) correct engine mounts? Even getting to parallel puts a lot of working angle in there...in cars like these where the axle is lower than the trans, they almost always set them up with the trans flat or tail-down.

 

[#41]

It's kind of hard to understand nose up / nose down description, but assuming the angles are going the right ways, I'd start with the simple, low cost solution of axles shims and see how that goes.

 

[yella71]

If the OP doesnt race then why the cal tracs?

 

[threewood]

You want the trans angle to be parallel with the pinion angle under acceleration. So of the trans is 5° down you should look for 2° pinion down assuming 3° wrap up when accelerating.

 

[Smokinnjokin]

Okay I just read your OP again, and judging by th`e fact you're wanting to shorten the trans mount, it does seem you mean truly 'nose down
Do you have the correct mount in there? Or (thanks Kimmer) correct engine mounts? Even getting to parallel puts a lot of working angle in there...in cars like these where the axle is lower than the trans, they almost always set them up with the trans flat or tai h

The transmission angle surprised me as well. Car had a very poorly done 318 to 360 swap, I have had to correct nearly everything from throttle brackets to kickdown operation to hardware used... maybe wrong motor mounts? I have never had any clearance issues with exhaust, and the fan appears parallel to radiator. Here's photos. Transmission mount has it sitting about 1.5" above the crossmember. That's why I asked, seemed like a pinion shim may be a band-aid to an extreme transmission angle.

 

[Smokinnjokin]

Just measured, centerline of crank is correct 5-1/4" above top of k-member. So... the transmission mount is too tall? The beer math says decreasing the transmission angle from 5 to zero would require a 2.5" drop of the rear mount... this isn't even possible with the tail shaft sitting 1.5" above the crossmember. Now I am thoroughly confused.

 

[oldkimmer]

I asked for more info in post 5. Not everyone knows your car. Is this a B body? C, E, F,M,J, a truckYou probably have A body motor brackets. They will lower the motor some and make the tranny tail shaft go up. If u were to/could drop the tail shaft 2.5 inches u would be tail down 100 or so degree’s. Does the crossmember seem right? Is the mount in all the way? Is it the right mount.

 

[beanhead]

That is strange to me, and I will readily admit I haven't as much experience with the 66-67 Bbods as some of the other guys here...but my '68 crank CL is close to your measurement, 5" and change. I don't think they'd be much different?
Maybe some of the better-qualified 67 guys can chime in on if those engine brackets are right or not, as you can see the one pretty clearly in the picture.
Other than that, all I can think of is it has to be the trans mount? I can see in that last pic that the tailshaft is pointing up.
Either that, or some strange issue like the crossmember isn't right? Hmmmmm whatever it is, I'm pulling for you to get it figured out!

 

[furyus]

If you put a level on the carburetor flange, it should be at 0. The tailshaft should be up to 3 degrees tail down. I would get that corrected before doing anything with the driveshaft, or differential.
Tremec has an app that will show you which part of the engine/drivetrain is out of spec.
It will show red for wrong, and green for good. It uses the smartphone for a digital angle gauge. I used it on my truck, and it worked perfectly.

 

[33 IMP]

When I changed from pushbutton trans to a later one with a different trans mount location and style, I just turned the crossmember around and welded on the bracket I needed, without messing up the pb side.
You could cut the mount off the crossmember and lower it a bit....... but I would FIRST make sure the engine mounts are right. As others have said, having the tailshaft end UP from level is not normal.

 

[Geoff 2]

If the stock factory mounts are being used, not a good idea to modify those to fix a drive line angle. The problem will be elsewhere & that is what needs fixing....

 

[Smokinnjokin]

Found the issue, stupid me I was measuring the transmission angle using the pan.. turns out the pan and valve body are not parallel to output shaft.. by 6 degrees. The actual angle, measured at the rear pad, was nose up by 1 degree. With the rake of the car, that is exactly what is normal. With this revelation, my driveline angles are all correct. 2 degrees of wrap-up brings me to parallel.

To address the earlier naysay asking why I have Caltracs on a street car (Why do any of us have any of the power or performance adders we have on street cars) consider this. I can stomp on the gas from a standstill and accelerate under full power, perfectly straight, with my hands off the steering wheel. The #3700 car has a mild 360, 3.23 sure grip with 28" tall tires and does a 6.2 second 0-60 (no launch, just mashing gas in D) consistently, every time. Just hooks, and goes straight. High speed turns, such as freeway on-ramps, are rock solid with minimal body roll. This is 100% due to to the suspension setup. You don't have to drag race to appreciate improved handling.

 

[threewood]

Found the issue, stupid me I was measuring the transmission angle using the pan.. turns out the pan and valve body are not parallel to output shaft.. by 6 degrees. The actual angle, measured at the rear pad, was nose up by 1 degree. With the rake of the car, that is exactly what is normal. With this revelation, my driveline angles are all correct. 2 degrees of wrap-up brings me to parallel.

To address the earlier naysay asking why I have Caltracs on a street car (Why do any of us have any of the power or performance adders we have on street cars) consider this. I can stomp on the gas from a standstill and accelerate under full power, perfectly straight, with my hands off the steering wheel. The car has a 360 with a mild cam, and does a 6.0 second 0-60 (no launch, just mashing gas in D). Just hooks, and goes straight. High speed turns, such as freeway on-ramps, are rock solid with minimal body roll. This is 100% due to to the suspension setup. You don't have to drag race to appreciate improved handling.

I'm pretty sure I measured my angle from the harmonic balancer face (crank parallel to input/output shaft) Glad you figured it out.

 

[Smokinnjokin]

Need to look elsewhere for vibes I suppose now... u-joints, tire balance, etc. It's not terrible but noticeable going 65+ mph.