Correct Drive Shaft

[deffmike]

Hi, this is my first post here. I recently picked up a 70 monte with a 350 that needs a lot of work. One of the first things I did was TH350 rebuilt. Now that I've reinstalled the tranny, I noticed the driveshaft has a drum on the front that offers less than 1/4" clearance to the bottom of the floor. I've inquired with the transmission shop with pics and everyone I showed it to confirmed the crossbar was in the correction orientation and the transmission installed correctly. 

My question is this, is the correct the driveshaft for a first gen monte with a stock drivetrain?

it looks exactly like this.

68 69 70 71 72 CHEVELLE COUPE DRIVE SHAFT MONTE CARLO TH350 MUNCIE 4 SPEED SS396 | eBay

Note, i re-installed all the same parts i removed, including the rear tranny mount. 

Assistance is much appreciated,

Thanks,

Mike

 

 

[Dtret]

Yes that is correct 

[deffmike]

Thanks for confirming. Just have one more question then, is the clearance between the top of that collar/cylinder and the bottom of the floor pan (about the height of my index finger as shown in the first pic) normal with the car on jackstands? 

 

 

Edited May 22 by deffmike

[jft69z]

1 hour ago, deffmike said:

Thanks for confirming. Just have one more question then, is the clearance between the top of that collar/cylinder and the bottom of the floor pan (about the height of my index finger as shown in the first pic) normal with the car on jackstands?

 

Look at the body mounts, see if they're all deteriorated and collapsed.

[Montemedic]

Mike, Welcome to the First Generation Monte Carlo Club. Plenty of knowledge and great information available here. Well worth $25 to become a full dues paying member to have total access and be able to participate in Club activities. There is a strong active group of local Club members that live near your hometown, myself included. Give me a call to discuss. (631) 445-1958. 

[420ponies]

Even with a regular driveshaft (no collar), it's close. I use a Poly style transmission mount ( Energy Suspension ), gives it just a little more room there.

[Dtret]

I can crawl under my 71 later. Do you have the jack stands holding the car up on the rear differential? Front doesn’t matter. 

[deffmike]

12 hours ago, jft69z said:

Look at the body mounts, see if they're all deteriorated and collapsed.

yeah theyre not in good shape

[deffmike]

just on the frame rails

[jft69z]

1 minute ago, deffmike said:

yeah theyre not in good shape

In that case, those aren't helping your clearance problem either.

[deffmike]

OK thanks , i guess that will have to be the next thing to address.

[jft69z]

If it's not physically rubbing on the floor board, it's not a big deal really.

[Dtret]

I have about 3/4 inch clearance. So not much. Hope this helps. 

[Dtret]

Remember also the yoke and the u-joint are behind that so it won’t move in any direction unless you have a major malfunction 

[deffmike]

Just to reopen the topic, i thought i had clearance when it was installed. Somehow when i actually tried to run in gear today (in the air) the front of the drive shaft totally jammed up again the floorboard. Since the transmission is mounted flush with the engine and the crossbar determines the height of the transmission, its seems like there's no solution. I've been working on cars for a while I've never run into a brick wall like this before. Could it be frame-damage somehow? I know the car was hit from the side at some point in its life. I'm probably at this point going to bite the bullet and bring it to the place where they rebuilt the tranny and have them reinstall it, or even sell it, if i can get anything for a non-moving car. Normally i don't give up but this seems more than i can handle. But ill give it one last effort before i do. I was thining of trying this

TH350/TH400 Pontiac/Buick/Chevy/Olds Turbo 350 Low Profile Transmission Mount | 350400700R4 | Aluminum | 10 Years | United States | Bolt-On | Lower

 

[cbolt]

I know I am late to the party, but my driveshaft doesn't have the collar on it like yours does. If Dennis confirmed that its correct, I have no reason to doubt him as he is the purveyor of all things Monte Carlo.

Just saying mine is different. Informal. Collarless, like a t-shirt. 

Maybe you could get your hands on a driveshaft without the collar and see if it still rubs? 

Another thought. On my Ford that does indeed have a bent subframe I installed shims (washers) on the trans mount to keep the driveshaft from hitting the floorboard. Maybe you could try that as well? 

[deffmike]

ill give your suggestions a try, glad im not the only one to face this. And yes i've got one from my chevelle which happens to be the same length

[montebob70]

There are two different height transmission mounts, short and tall. Which mount do you have?

Bob

[Marks71]

My 71 has the collar, and there’s maybe 1/2” clearance because I can’t quite get my index finger between the floor and collar. This is on my 4 post lift so the car sits as it would on the floor so there are no variables that could affect clearance. Did the trans shop replace the trans mount with a thicker one? Could the cross member be slightly bent? Or as Joe suggested the body bushings be collapsed? Because the collar is for balance, if you do away with it, you’ll want to have the drive shaft rebalanced where they tack the weights directly to the tube. Because the collar is the way the factory built it, I’d do my best to find out why there is an issue. 

[cbolt]

1 hour ago, Marks71 said:

 Because the collar is the way the factory built it,

Dumb question; was the collar used at different plants? My drivetrain was stock when I got my car and it doesn't have the collar, never did. It has weights on the tube like every other '70s GM car I ever owned so I wonder if the collar was plant-specific. 

[Marks71]

21 minutes ago, cbolt said:

Dumb question; was the collar used at different plants? My drivetrain was stock when I got my car and it doesn't have the collar, never did. It has weights on the tube like every other '70s GM car I ever owned so I wonder if the collar was plant-specific. 

Not sure, mines a Kansas City build. 

[Dtret]

I think the collar may have been prone to higher horsepower cars. I have seen some without them. It’s also possible that they were being eliminated towards the end of the first generation run. Do not know anything about being plant specific. A collarless should work fine as long as it’s properly balanced to the drivetrain. 

[jft69z]

1 hour ago, Dtret said:

I think the collar may have been prone to higher horsepower cars. 

My old 350 2bbl Custom had the collar.

[deffmike]

the mounts are bad yes, but i just don't have the room right now in the garage to try to change them. as far as the height of the trans mounts i didn't know there were 2 different heights. if I were to guess I have the taller one, or so i hope. I hope the low profile one I just bought might help. From the sound of it looks like it may be a combination of things. Crossbar being bent i cant say- that might be the next thing i try to look into. It didnt show any obvious signs of being uneven or damaged in any way, but i dont know

[deffmike]

Additional info: turns out that the motor, after I finally decoded it, is not a 350 but a 400 SBC based on the casting number of 3951511. The engine stamp with the "CKP" suffix tells me it was apparently swapped in at some point. If the motor mounts and frame mounts are different for a 400 Small block vs a 350, I'd bet money that whoever did the swap didn't bother to change them to the correct ones. Still googling to see if they were different between the two motors.

CKP

1972

400

tur hydro trans.

170

2

Caprice