Help: Transmission not centered?

[Grabinov911]

Guys I put more details in my "80 Grit" thread, but when installing a new Gear Vendor tailshaft housing this weekend it became clear that the housing was not centered in the driveshaft tunnel.

This photo shows the factory tailshaft housing, but unfortunately it's not a very good angle to see if the housing is centered.

View attachment 291259

This is the new housing, from the correct angle. The lighting could be better but you can see (poorly) that the housing is to the right (of the tunnel / car) by about 3/4" from center.

View attachment 291258

I'm really confused. How can this be? The only mounts still in place (since the trans mount and crossmember are removed) are the engine mounts, and they only go on one way. How can the whole system be turned to leave the tailshaft housing off center? It's as if the whole engine is turned left (moving the tail right).

Are the engine and transmission off-center from the factory? Doesn't the driveshaft go down the exact middle of the car?

 

[Badvert65]

Yes, the entire drive line is offset towards the passenger side, by design, in all Mopars (that I am aware of), Also, there is some flex/adjustment in the engine mounts.

 

[Daves69]

This might give you an idea of the offset...................

http://ttiexhaust.com/Footnotes/39.htm

 

[HEMI-ITIS]

The engine does not sit centered in the engine bay,it's offset to the passenger side.

 

[Cranky]

The trans tunnel shouldn't be centered either.....at least it's not centered in my Belvedere and it still has the factory floors in it.

 

[Grabinov911]

Thank you Gents.

Obviously you guys are correct. The engine and trans are apparently offset to the right in the car. But as Cranky points out, the tunnel shouldn't be centered either, meaning the trans and driveshaft should STILL be centered in the tunnel! At least I would think.

According to the chart Dave69 provided (thanks Dave), for a 66 to 74 big-block B body, the engine is offset 1.25" to the right. Strangely, they then say that the distance from the crankshaft to the left and right framerails is 2.5" different (to the right). Not sure how the engine and crankshaft offsets can be different. Maybe the framerails are different.


I'm gonna go back and check some measurements, among them, the distance to the center of the tunnel, and the center of the crankshaft.

 

[Kern Dog]

Also, there is some flex/adjustment in the engine mounts.

Absolutely! Unbolt the trans crossmember and watch the tailshaft move?
I think there is tension that builds up and the trans mount sorta keeps it in check. When I did my GV install, I took all sorts of measurements and still ended up mounting it too low. This resulted in some driveline vibrations that were exacerbated by my incorrect pinion angle.
No, really... I know what I am doing! :headbang:
I'm always learning. Things I do today will be determined to be not as easy as methods that I learn tomorrow.

 

[cryplydog]

Hi GRABINOV911, Without going into a crap load of reasons of why this condition does occur in all cars when changing engine systems/trans and all the mnting brackets I jack up the front on the frame rails to take most of the weight off and then loosen the 4 k/frame bolts and then maybe even loosen motor mnts. then get under car at rear of trans and it will come around enough to drop right in place, seems to work every time . I think after mkt. motor mnt pads and block brkts have a lot to do with this cond. Get it set so tailshaft housing and cross member will go in then go around and retorque all that was loosened. good luck with mods and tell us how you like the gear vendors equip. Also, the drive shaft geometery should be right where it needs to be except for shortening. You may have to use a pry bar to help k/frame to come around.

 

[Grabinov911]

Hi GRABINOV911, Without going into a crap load of reasons of why this condition does occur in all cars when changing engine systems/trans and all the mnting brackets I jack up the front on the frame rails to take most of the weight off and then loosen the 4 k/frame bolts and then maybe even loosen motor mnts. then get under car at rear of trans and it will come around enough to drop right in place, seems to work every time . I think after mkt. motor mnt pads and block brkts have a lot to do with this cond. Get it set so tailshaft housing and cross member will go in then go around and retorque all that was loosened. good luck with mods and tell us how you like the gear vendors equip. Also, the drive shaft geometery should be right where it needs to be except for shortening. You may have to use a pry bar to help k/frame to come around.

Holy Crap are you kidding me? I mean this is GREAT info, and seriously appreciated but WOW that's a LOT of weight to be shoving around. It never occurred to me that the K Frame may be in the wrong place. I'm using Dynatech MityMounts engine mounts and I suppose they could be the problem too.

Does that actually work? With the torsion bars in and the front suspension all hooked up? I'm scared!

Here's a picture below from an online article showing the trans tailshaft (granted it's a manual trans but whatever) perfectly centered in the tunnel.



That's what I'm looking for. CENTERED!

 

[Kern Dog]

Hmmm...

- - - Updated - - -

??

 

[Grabinov911]

And here's another one, WITH a Gear Vendor, from this thread:

http://www.forbbodiesonly.com/mopar...87-1968-383-Charger-Gear-Vendors-installation

View attachment 291557

CENTERED in the tunnel.

And FINALLY, here's a good picture of mine. Sorry for not exactly level. At least the lighting is better!



That is just touching the tunnel on the right and 1.25" from the left. Something is wrong with my engine position! Either the whole engine and transmission are 3/4" too far to the right; or the engine mounts are out of whack and the engine is "turned" to the left (moving the tailshaft right); or the whole K-Frame is turned to the left (moving the tailshaft right). From the engine mounts to the end of the tailshaft has got to be five feet or more, so even if the engine or K-Frame is turned only a few degrees, it could account for the problem.

If you're thinking what I'm thinking: The car has all of the original floor sheet metal, frame rails, core support, etc. I don't think it was ever in a collision...

 

[Kern Dog]

The holes in the motor mount brackets are slightly larger than the bolts. The holes on the block for the mounts are slightly larger too. This can and will allow some slop. Think of it this way: If the engine is off by 1/4 inch at the mounts, that can translate to being off at least an inch or more 3 feet rearward at the end of the trans.

 

[HT413]

According to the chart Dave69 provided (thanks Dave), for a 66 to 74 big-block B body, the engine is offset 1.25" to the right. Strangely, they then say that the distance from the crankshaft to the left and right framerails is 2.5" different (to the right). Not sure how the engine and crankshaft offsets can be different.

Sure, if the crankshaft is offset 1.25" to the right of center, that adds 1.25" to the left dimension and at the same time subtracts that same 1.25" from the right side. Thus we have a 2.5" difference.

- - - Updated - - -

The holes in the motor mount brackets are slightly larger than the bolts. The holes on the block for the mounts are slightly larger too. This can and will allow some slop. Think of it this way: If the engine is off by 1/4 inch at the mounts, that can translate to being off at least an inch or more 3 feet rearward at the end of the trans.

Great point, Greg (and all the others). I hope to get my 451 together this winter and this may have helped me avoid hours of cursing.

 

[Grabinov911]

So tonight, it's Loosen, Push, Pry!

There is really no way to loosen the bolts at the engine block (mount to block) while the engine is in the car - particularly with power steering on the driver's side - so I'll try to loosen the mount to K-Frame bolts first. The engine went IN this way (from the top with the mounts already on the engine), so I should be able to get to them. They have "captive" nuts if I remember correctly, so only need one wrench (the nut can't move).

The car is on the wheels on blocks, so as I loosen those bolts, the engine should literally be resting on the mount pads and on the jack under the trans.

Glad I took a lot of pictures. Here are the mount pads - Passenger Side



Driver's Side

 

[Cranky]

The K frame shouldn't be able to move around much at all if any when it's bolts are loosened. If it does, you may have more problems than you care to address. Everything has a tolerance and even though the body panels have more, the chassis does not have much. If the K is off enough to mess up engine/transmission placement, it's also going to play big games with the front end alignment.

 

[Mocajava]

This thread really opened my eyes and provided an education to me. Thank you ALL for your in-depth explanations. I will be following this thread to fruition and hope to see everything lined up and the how-to's of doing it correctly.

 

[Grabinov911]

OM Frickin' G!

The holes in the motor mount brackets are slightly larger than the bolts. The holes on the block for the mounts are slightly larger too. This can and will allow some slop. Think of it this way: If the engine is off by 1/4 inch at the mounts, that can translate to being off at least an inch or more 3 feet rearward at the end of the trans.

OM Frickin' G! It works...



I loosened the motor mount to K-Frame bolts - one on each side of the engine. It turns out it takes about 2 minutes. They are REALLY easy to access. then I put my leg under the car and pushed till the tailshaft housing was banging on the far (left) side of the tunnel. Slammed it about ten times and voila. Done. When I tightened the bolts it came back a fraction, but not nearly to where it was. There is also a LOT of play in the rubber portion of the engine mount even when tight. I could bang the housing into EITHER side of the tunnel by pushing it with my leg. I see why guys switch to motor plates. That's a lot of torque loss.

Thank you Gentlemen. Your assistance is nothing short of miraculous.

Now back to my previously scheduled installation - and my other thread (80 Grit)...

 

[Kern Dog]

You can thank me by paying the bill I sent you.

 

[cryplydog]

The K frame shouldn't be able to move around much at all if any when it's bolts are loosened. If it does, you may have more problems than you care to address. Everything has a tolerance and even though the body panels have more, the chassis does not have much. If the K is off enough to mess up engine/transmission placement, it's also going to play big games with the front end alignment.

Cranky, can you imagine what a .060 larger hole in the k/frame from the mnting bolt diameter would do 4' to 5' back in the drive line side tolerance travel. These allowances are there because they are needed for assembly. you can get a decent amount of adjustment by this method and I do it on all fit ups on these cars with a pry bar and someone at the gearbox and sometimes have to loosen the motor mnts. I know you are a very experienced mopar wrench but absolute dims. are not our friend in this type of assembly. I have never had the need to check the inside dia. of the k/frame holes and the OD of the bolt shoulders but next time I will check them with a dial caliper. Hi Grabinov, next time you are FITTING in a k/member put in the bolts and back them off a turn or so and make a couple witness marks with a scribe then move it back and forth diagonally to see what you have as possible adjustment. Good luck to all.