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C4 Corvette IRS install

5K views 5 replies 2 participants last post by  Magman 
#1 ·
I made a tool splash off my 86 Corvette frame to master the batwing and 4 link brackets as a unit to transfer to my custom frame. I noted the vertical measurement to the lower from the C4 frame sill below the door. This is a frame master datum location. I transferred the tool master and vertical dimension to my custom frame. Here are some notes and then some questions. Note 1) The Dana 44 output yoke is off center to right side. Note 2) the yoke is near zero angle based on the bolt flat where the center beam installs. This would mean a near zero angle for the engine crankshaft which is very unconventional. After thinking on it, the off center requirement for the engine trans vs the Dana rear is only required in one direction for the driveshaft. This is typically a vertical offset for the driveshaft but could be a horizontal offset for the driveshaft. That said, I have some questions. 1) Can anyone verify the factory angle up/down for the flat surface on top the Dana? This is the surface that has the 2 bolt holes mating the beam. It must be close to zero based on my tool splash. 2) Can anyone confirm the horizontal offset on the driveshaft for the C4 Corvette? Thanks- Steve
 
#2 ·
I got mine on the lift with the drive shaft out where do you want me to measure. I will get out the tape and take some measurements. I know the trans and rear are bolted together with a bracket that connects the two. so they are locked if the rear is off angle so will the trans and motor be off since its all one locked unit if the bolt holes in the bracket are straight which they appear to be but haven't measured it.

Are you making a new bat wing or using one from a c4. Also is this going to use the tranny brace to hold the front of the rear. In the car they are not held totally in place by the rear batwing.

Let me know i will take a look.
I don't know what you can measure that would be helpful. The car would need to be level and then a digital level put on the Dana with the beam removed... but thank you for the kind offer. What I really would love to have is the curb weight Engineering Specs for drive train angle. I have a nice side view drawing showing all the drive train and suspension on approx. 4" grid that is helpful for rough scaling. I found it on line somewhere. It looks to be about 1 degree angle on the driveshaft going up to the transmission. The engine sits very level in the Corvette. I am using the entire dana IRS set up including batwing, the spring and the 2 brackets attaching the 4 link to the body.
 
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#3 · (Edited)
ok, let me try to explain better. agreed, nothing moves but the axle shafts. The batwing is installed dead center and symmetrical to the car and to the left and right 4 link brackets on the body are also symmetrical. The output yoke on the dana that connects to the drive shaft is off center to the right an inch or so. You can measure and verify the distance from the dana yoke center to one of the 4 link arms on each side of the car just use the same position to measure both sides. You will see that the center of the dana yoke mating the driveshaft is off center to the right. This is quite unconventional. I am an old tooling guy from aerospace. A splash is a tool made from a master tool. In this case the corvette is the master tool and the splash is a tool I made to transfer the critical points on the corvette to my new frame. This way I have exactly the same mounting points as my car. The points I mastered are the 2 batwing holes including the 4 faces of those holes that mate the batwing. Next I mastered the 4 holes of the 2 removable brackets and there 4 faces that mate the 4 links. All these 6 holes and faces are on the same tool splash. So when I remove the tool splash from the car I have all critical points mastered to duplicate the exact geometry from my 86 corvette. If the car is off then so is my tool but the transfer of geometry is an exact match. please measure your car. I am anxious to hear your dimensions. Your numbers are not critical but to confirm the offset of the yoke to be significant to the right.


added info. The engine and trans are not off angle to the dana. They are probably on center of the car. All that is important is that the center line of the engine/trans vs the centerline of the dana are parallel. If all are on the same level and same centerline then the u-joints are unloaded and the needle bearing cannot rotate. This will destroy the u-joints. Convention practice is to have the center lines parallel such that the drive shaft is at approx. 3 degree angle in one direction so to load the needle bearings for proper rotation. It does not matter if the angle is side to side as in this case of C4 corvette or up and down parallel as in most cases as long as the driveshaft angle condition is met. This is the unconventional part but still will work. It is most interesting.
 
#4 ·
I know what you're trying to do; but I don't have any definitive references to help you out. Sorry.
That said; there was a hot rod genius that built a "pro touring" car before they existed; using the C4 suspension and a blown smallblock chev with a directdrive 5spd Richmond and 3.08s. His name was Lil John Buttera and the car was called the NoVette. If you can find the original article; it may give you some insight.
Don't think John was a ham fisted hotrodder? He built a competitive indycar back in the 70s and was probably in the last group of privateers to do so.
 
#6 ·
I am not using the beam that connects the Dana to the transmission. I am running an LT1/4L60E out of a 94 roadmaster. My Doug Nash has a blown overdrive and it connects to the beam with 2 long bolts same as the rear Dana attachment. Yes the right side is the passenger side. I don't know how to check the engine position either. Maybe a measurement from the upper control arm to the head on each side?I never checked the shock mounts vs the yoke on my car. I assume there are symmetrical about the car center line same as the 4 link just forward of the tires. I will measure mine again this evening and get an exact measurement from the yoke to all those points and report back. I sold the L98 when a friend offered me the LT1 combo cheap while I was searching for a replacement transmission. I still have all the Nash stuff including the shift linkage, pedals and beam, etc to change over from automatic to 4+3. nOT sure what I am going to do with it. The vette was very rough, purchased cheap and cut up for a donor to use on my 34 Ford hotrod. all that remains intact on the vette is the bare shell of the frame after butcher to get critical attach points for the Dana. My 34 ford is being built with the 112" wheelbase same as the factory V8 model 40. The C4 is on a 96.2" so the beam wont work or I would have sprung for repairs to the overdrive unit. The overdrive unit is definately bad, reverse is out and I hear this is what happens when they get real bad and fail the carrier bearing.
 
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