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Driveshaft Angle Question

Steve Blair

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Good morning everyone,
I have been working on a 71 Barracuda (Cuda clone) and the car has a Gear Vendors over/under drive behind a 727 automatic transmission, GV says to elongate the crossmember mounting holes and dimple the tunnel where the GV unit touches but I could see it would take more than they suggested to gain adequate clearance so I redrilled a lower hole for the motor mount. I also feared that new rear leaf springs would jack the rear of the car up so I used PST 1 inch lower springs instead of the factory Super Stock springs. Well the bottom of the GV intermediate extension housing was vibrating on the top of the crossmember so I had to grind a small amount off the bottom of the extension housing for clearance. As a result the GV is a Negative 4 degrees, the driveshaft runs uphill a positive 3 degrees, and the Dana 60's pinion is a positive 4 degrees. My question is will the negative 4 degrees at the GV output cancel the positive 4 degree of the pinion even though the driveshaft is running uphill 3 degrees between the GV unit and rear differential or should I replace the rear leaf springs with Super Stock units to lower the differential and reducie the driveshaft angle between the GV unit and rear differential? Has anyone else used the PST 1 inch lower leaf springs without any problems?
Any opinions are appreciated.
Thank you
 

Steve340

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Use the Spicer driveline calculator on the internet.
It also has guidelines on the correct set-up and angles.
 

Steve Blair

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I did use the Spicer driveline calculator, it says the angle of my U joint at the rear of the transmission is 7.2 degrees, and the pinion angle is .6 degrees. Since my rear end is way up in the tunnel (because the PST 1 inch lower springs are too soft) I will try some of the Super Stock springs to bring the rear end back down out of the tunnel so I have a better angle on the driveshaft and pinion. I already made as much room in the tunnel as possible by pounding the tunnel outward but unless I remove some of the tunnel sheet metal and make more room for the overdrive unit there won't be enough room. My opinion is the Gear Vendors Overdrive will not fit the tunnel of an E Body by putting a couple dimples in the tunnel sheet metal where the GV unit makes contact. I will try getting the rear end lower in the tunnel to improve my front driveshaft U joint angle first, if the Super Stock leaf springs don't improve my U joint angle I may have to modify my transmission tunnel so I can raise the GV overdrive enough to reduce the U joint angle at the output shaft. This is a lot more work than it was supposed to be but with 4:10 gears in the rear end the overdrive makes the car drivable!
 

Steve340

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Follow those Spicer set up rules and you cannot go wrong. I believe the recommend operating angles on the U joints need to be within 1 degree.
 

cuda joe

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not a fan of lowering springs in an e body they sit low with stock springs learned the hard way
 

Steve Blair

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Looks like I'm learning the hard way too, how would you go about choosing the correct springs? I was thinking Super Stock springs would raise the car some and help control axle wrap since the Dana 60 I have has no provision for a pinion snubber. Mancini Racing sells springs for different weight cars, I suspect a 71 440 Cuda with a 727, full interior, and Dana 60 weighs close to 3,600 lbs.?
 

cuda joe

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I built mine for the street someone else needs to chime in for racing best of luck
 

Steve Blair

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Mine is really for the street too! I think I will have to replace the leaf springs to get the differential away from the tunnel since the Dana has no provision for a snubber I will have to figure out how to control axle wrap without the snubber. I should have installed a 4 link but I've never done that and I had no idea what I was in for using lower leaf springs and an axle housing that had the spring perches installed improperly. I think I'll change the leaf springs, move the spring perches and see if I can't get everything angled correctly.
 

cuda joe

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for the street you don;t want super stock springs. and to change pinion angle you use shims no need to move the perches
 

Steve Blair

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The Dana 60 was rebuilt and shipped from Canada and though the width was correct the angle of the spring perches was wrong (it was from a truck, no provision for the snubber). My car is a problem anyway because the GV unit won't tuck up into the trans tunnel no mater how much I try to message the metal, the output on the GV unit ends up at 4.40 degrees down which puts the driveshaft uphill into the tunnel (I was barely into the gas and the driveshaft hit the tunnel because the Dana 60 has no provision for a snubber and it's so close it doesn't take much to hit). Maybe Super Stock springs will make the rear of the car too high? I will contact Mancini Racing tomorrow and see what they say, they carry 3 sets of spring made for different weight cars. I think my car weighs 3,400 to 3,600 lbs. but it has not been weighed. It has aluminum heads, TTI headers, and a CH4B aluminum intake so I think it may weigh less than their 3,800 lbs. springs. I really like the ride of the 1 inch lower PST springs but I need more clearance for the diff. The driveshaft runs uphill to the diff, without cutting the floor out to lift the GV unit and improve the angle of my driveshaft I won't be able adjust the trans and diff angle to cancel any vibration.

Does anyone know what the angle of the back of their transmission, driveshaft, or pinion is from the factory?
 

Steve Blair

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Maybe I should buy a new Dana 60 with pinion snubber and perches welded on where they belong? If I cut out the floor and raised the GV unit then patched the floor I could probably use the 1 inch lower leaf springs from PST?
 

Steve340

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Factory angles for most manufacturers is in the 2.5 to 3 degree range for both engine/trans and pinion.
 

Steve Blair

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So I think I need the pinion snubber on the diff to control axle wrap, I think I may have to buy the correct diff and see what problems I have with the trans at neg 4.40 degrees. I also have poly motor mounts but I don't believe they raised the motor any. I used the poly engine mounts because the 2 inch TTI headers are within 1/4 inch or less of the power steering sector and I didn't want the header tubes to contact the steering gear if the motor shook at idle. The poly mounts appear to keep the motor from shaking at idle and under power if the motor moves it would move the header tube away from the steering sector. The motor developed 540 horse at 5,500 rpm, and 600 ft lbs. of torque at 4,000 rpm so I think axle wrap is an issue I need to resolve that a pinion snubber may be the only way? I was told I would not need the snubber with Super Stock leaf springs so I thought they might resolve my lack of pinion snubber issue.
 

heminut

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If things are set up correctly and you're not drag racing you don't need a pinion snubber. Not having a pinion snubber is the least of your worries and you should quit dwelling on that and worry more about correcting the other problems.

The first thing you need to do is do whatever you need to do to get the transmission back up where it belongs, everything else depends on that. Once you do that, then you need to do whatever is necessary to get the differential angle set properly. Others have posted what the factory angles should be. At that point, if the differential is to close to the floorboard tunnel then I would say you definitely need different springs.

Solve one problem at a time before trying to solve all of them all at once.
 

heminut

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I also feared that new rear leaf springs would jack the rear of the car up so I used PST 1 inch lower springs instead of the factory Super Stock springs.
Superstock springs were not factory, they were an aftermarket add on. The one inch lowering springs were usually utilized for road racing.

Another thing I just thought of, the Mopar superstock springs are two inches shorter on the front section (20" as opposed to the stock 22") and require changing the front spring box to a longer one to make up for the shorter front section. If the springs you have bolt in okay then they most likely aren't the superstock springs sold by Mopar Performance.
 
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cuda joe

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on these cars the trans does point down a little .try this test get your angle on the trans then raise the back end up 3 inches then remeasure trans angle again . measuments should be made with drive shaft removed .measuring on the vertical edge
 

cuda joe

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i had a problem with pinion angles also the trans points down a little you can;t raise it up so i did it this way with trans pointing down a little the drive shaft guy said it;s ok the trans angle and rear angle should be about equal one up and one down like - 2 deg and + 2 deg

Scan_20230719.png
 

Steve Blair

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If things are set up correctly and you're not drag racing you don't need a pinion snubber. Not having a pinion snubber is the least of your worries and you should quit dwelling on that and worry more about correcting the other problems.

The first thing you need to do is do whatever you need to do to get the transmission back up where it belongs, everything else depends on that. Once you do that, then you need to do whatever is necessary to get the differential angle set properly. Others have posted what the factory angles should be. At that point, if the differential is to close to the floorboard tunnel then I would say you definitely need different springs.

Solve one problem at a time before trying to solve all of them all at once.
Thanks for your advice, fixing the angle of the GV unit may take cutting the floor. Guess I'll fix that angle first!
 
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