Transmission Alignment

[Tonker1]

This is an email I slightly modified email which I sent to American Powertrain. While I wait for their reply I was looking for a second opinion.

The bell housing is installed and dialled in to the correct 0.005" tolerance, but I've been having some problems with the test fit. Compared to the centerline of the drive train the transmission appears to be sitting 3/8"-1/2" towards the passenger side of the car which is preventing the transmission cross-member being bolted to the isolator mount. The displacement of the transmission can be clearly seen in attached photos 1 & 2. In the second photo the line of string represents the centreline of the drive train, tied to the diff and crank pulley. The reason that I post this because of the tech video Chryco Psycho posted http://www.cuda-challenger.com/cc/index.php?topic=93146.0.

My first two questions determine whether the rest of this post is necessary.

1. For 3/8" to 1/2" of offset is it okay leave the transmission where it is and let the universal joints absorb the offset?

If the answer is yes :  I will cut some material off the cross-member to create space for the isolator mount bolts.

If the answer is no: please continue reading.

By pushing against the transmission, the cross-member and isolator mount holes can be lined up. Unfortunately the shifter tower contacts the cross-member before the the previously mentioned bolt holes are centered with each other. I am planning to cut the metal (as outlined by the black marker on yellow electrical tape in photo 3) to provide clearance for the transmission to be moved across. Removing a small seciton from the shifter tower should not be a problem becuase the metal used to make the sfiter tower is almost twice as thick as the chassis rail and the tower is low stress area.

The shifter tower contacts the chassis at the point marked in photo 4 & 5. The contact occurs at the edge of the shifter tower at the bolt hole marked in photo 4. Photo 5 further illustrates the location of the contact, a small section of the edge of the shifter tower which is obscured by the bolt. It's extremely hard to get a clear photo down there.

One more question:
2. The transmission at rest wants to be out of line with the centerline of the drivetrain . After the above modifications to the shifter tower and bolt area have been made the only thing holding the transmission so that it would be in line with the centerline of the drive train would be the isolator mount. Would this put excess stress and damaging stress on the isolator mount?

Thanks in advance.

[brads70]

I have never seen a factory engine that wasn't offset to the passenger side that had a steering box.  Maybe whoever made the tranny mount assumed it would be in the center of the car?   Measure the center of the pinion on the rear end, I'd bet that too is offset ?

[CudamanTom]

The transmission appears to be sitting 3/8"-1/2" towards the passenger side of the car

The engine/tranny usually sits offset to the passenger side just a tad. You can't go by a center line string.

Edit: this also explains why the shaker base sits offset for the shaker bubble will be centered with the hood.

[CudamanTom]

I have never seen a factory engine that wasn't offset to the passenger side that had a steering box.  Maybe whoever made the tranny mount assumed it would be in the center of the car?   Measure the center of the pinion on the rear end, I'd bet that too is offset ?

 
I agree with Brad on the manufacturer of the tranny mount.

[Tonker1]

.

I have never seen a factory engine that wasn't offset to the passenger side that had a steering box.  Maybe whoever made the tranny mount assumed it would be in the center of the car?   Measure the center of the pinion on the rear end, I'd bet that too is offset ?

That's a good point. The string should represent the centre of the drivetrain as it runs from the centre of the diff pinion to a plumb bob centre of the accessory pulley nut. The output end of the transmission appears to be out of line with the rest of the drive train.

[bigblue73]

Please forgive me for asking but has your car ever been in an accident?  Floor pans replaced?  The offset is only 3/16 of an inch and this is from factory information.  I've never seen one off this far before in the 5 E-Body installs that I have done.  Could your K-frame be pushed to passenger side of the car?  I'm baffled.  True to form the bolt holes should be showing - not covered up completely.

[Cuda54]

You did not get the motor mount in backwards did you? That would off set the whole power train. Just thinking out load. Been there done that too.

[Tonker1]

You did not get the motor mount in backwards did you? That would off set the whole power train. Just thinking out load. Been there done that too.

I'm yet to touch the motor mounts, but when I bought the car it was someone else's project. How should the motor mounts be oriented?

Thinking on the same concept, could a motor mount have sagged with age? And if so how would I tell if it had done?

Thanks in advance!

[Tonker1]

I put a bolt into the back of the transmission output shaft and measured the separation between the output shaft and the centerline of the drive train. The output shaft is almost exactly 1/2" to the passenger side of the vehicle with respect to the centerline of the drive train.

One option that I'm working on, as suggested by Cuda54, is that the motor mounts may have been installed incorrectly, so I took some photos. Would anyone be able to identify if the mounts are installed correctly and on the correct sides of the vehicle from just looking at the photos. I'm aware this is probably a tall ask.

Photos 4-6 are of the passenger side motor mount. There are some numbers on the rubber section of the passenger side mount, I'm not sure if they are helpful, but it can't hurt.
Should the top section of the rubber on the passenger side mount over hang like that (the section circled in red)?

The last photo is of the drivers side mount, I could only get  one angle with the header installed. If another angle is required I'll pull the header.

Any thoughts or ideas would be appreciated.

[brads70]

I have had some experience in circle track racing and for years we used Camaro front subframes. I have seen up to 1" differences between the steering box mount and the idler arm mount stock.  My point is back in the day if you will, production tolerances sucked!  1/2" that far back ( figuring in a bit of trig) I wouldn't get too concerned. I'd just slot the holes and go.    Maybe replace the motor mounts if they look questionable? Another option is to shim the motor mounts, I did to better fit the headers. Again factoring in a bit of trig if you shim the motor mounts an 1/8" on one side  and by the time you get to the tail stock it could be quite a bit. So factor in the saggy oil soaked motor mounts, maybe they are the problem?

[Chryco Psycho]

Sorry I should have looked more closely at this but I have been over tired .
Going back to the original post -
 Question 1 - I would say no allowing the driveshaft to take up the off angle is bad & may create a vibration , I would trim the shifter bolt housing & move the trans over to center it .
 Question 2 - yes it will put stress on the mount but not enough that the mount would fail quickly , it may not last quite as long but it is still a better situation .
 I agree with Brad that 1/2" 3 feet back from the mounts would only be 1/16-1/8 " , the drivers side should have 3 bolts with a 4" long  through bolt in the lower hole , the passenger side uses 3 individual bolts approx 2" long . The mounts you have look older & to move the rubber 1/16" is nothing , replacing the mounts might be a good call anyway have you tried jacking the motor slightly to see if the mounts are still attached often they look Ok until you get on the loud pedal & they are close to separating anyway .

[ek3]

I too have worked on many Camaro front sub sections!!... yep , oval track!.. I can suggest that you loosen the motor mounts / bolts, [use wood and  a jack- easy- under the engine or the hoist if you will ]  then pull the tranny in line , finger tighten the trans mounting bolts and see where that gets you with respect to alignment. the engine can move at an angle or side to side. your current line does assume the rear is located exactly where it is supposed to be.

[Tonker1]

Thanks for the excellent responses Brad70, Chyrco Psycho and ek3!

Combing the advice from the three of your posts, I'll start out by replacing the engine mounts. It's probably about time that they were replaced and the new mounts will slightly change the location of the engine. Keep the mount bolts loose and locate the engine and trans to correct alignment. Shim engine mounts as required to achieve the final location. This sounds like an effective plan.

Is their any particular brand of engine mounts for recommended for Mopar 340 engines?

I have another chunk of free time coming up on Friday afternoon so I'll jack the engine and check if the mounts are properly attached.

I honestly hadn't considered the possibility that diff may also be slightly out of line as well. Generally, I work with the theory of do it once and do it right. Correctly locating a diff sounds like a long, time consuming process. In order to maintain simplicity I may leave the diff as is. Is there anyway to get a ruff idea if the diff is located correctly without having to get too involved?

Thanks again.

[Mopar_Mudder]

You might want to give my thread a read as I had a similar issue. The tail of my tranny is slightly differnt then yours.

I never ran a string front to back to see where the tailshaft is sitting, good idea though. I will have to check that as I am still fighting with a vibration in the drive line.

http://www.cuda-challenger.com/cc/index.php?topic=89279.msg888123#msg888123