I replaced my body, engine mounts and trans mount when I had my body of the frame and now with body back on my U-joint at the trans is hitting the floor. Is there a difference in trans mounts for TH 350 in a 72 Cutlass?
As far as I know the parts are for a 350/350 Cutlass and now I have a 403 with a TH350 could that be a problem?

 

You would think, if anything your body would of went higher with the new mounts. Did you change anything else? Is the trans crossmember bent?

 

Did you keep the old trani mount? If you did you could compare them.

 

That was I what would think with new body mounts it sits higher, so more clearance and I did not had an issue with that before.
I did not keep the old mount so I could compare but the crossmember is the same as what was in before and not bent.
Is it maybe that I have the crossmember on wrong, it is bolted in the place where it was before.
I also put on new springs and shocks and new bushings in all the arms.

 

Could you have possibly bolted the xmember upside down.

 

It doesn't fit upside down because of the humps for the exhaust.
And I think the height is the same if just rotate it.

 

Most likely either the engine or trans mounts are wrong or both. If you viewed the driveline geometry looking from the oil pan of the engine straight down to the rear u-joint where is the high spot? If its the trans tail shaft than the problems the mount and or the cross member. What else did you change, trans? If the motor mounts are shorter that will raise the tailshaft. So you could have a two fold problem short motor mounts tall trans mount? Hows the clearance of the fan in the fan shroud?

 

When i installed my tranny mount there was an 1/8" steel plate in the kit that was supposed to go under the mount. If there were passengers in the backseat the driveshaft rubbed the floor brace when I went over a bump. I removed the shim and haven't had a problem since. That was a Muncie but I'm sure they all use similar kits.

 

Perhaps a few pics??

 

I changed my 350ci engine with a mild tuned 403ci, both smallblocks and used the th350 that came out with the 350ci. The mounts on the frame for the engine are the same and new engine mounts P/N:2261 and the trans mount is new P/N:2378 with the same crossmember as before. I know if you have a th400 that you have too use a shim. Can only work on my car in the weekend so I will try to make some pics. I thought there was no difference in mounts for smallblocks.

 

Fan shroud clearance ok?

 

The fan was original a 4 blade with no fan shroud and now I have a 7 blade with a clutch still no shroud.
So that is all different but I did noticed that when I wanted to hook up my speedo cable that there was little room for the cable.
Can I modify the trans mount so I have more room for the driveshaft?
Or modify the floor but there must be a reason that it will hit the floor.

 

I agree something has changed. It should not hit!

 

I would think you shouldn't have to modify anything. Before you do something drastic, is there a similar vehicle you could look at?
Can you get another set of mounts from a different vendor to see if they're the same? Wrong mounts are the only thing I can think of.

 

Yes, I think it's also some thing with the mounts I will check that tomorrow.
Because I live in The Netherlands and there are few Oldsmobile's a round I can't compare or find them at a junkyard.
Did repair the frame where the body mounts go because the body was hanging to one side before the frame off and did not hit the floor.
Put new mount from Supercars Unlimited all according too the discription under the body and the mounts I mention earlier.
Then the body has to be higher on the frame.

 

Could the floor be weak/rusty?

 

Pictures??

 

Here is a few pics of the floor and driveshaft.

 

Do you have any pictures of the rear of the transmission, the mount, and the cross member?

 

I did take pic of it but can't seen that much on there, have it on the ground and not much room.
Today I massaged the floor with a hammer and have enough room now.
Could not find anything wrong with the mounts or there position so this was the simplest solution.
Thanks for the help.

 

I now have some picture's of the trans and drive shaft because now it hits the body brace behind the trans when I drive over a dip in the road.
I think the trans mount is too high but don't have a picture or car to compare.
Can someone tell me if all the mounts are fitted correct?

 

Do you have any pictures of how the trans xmember is attatched to the frame on both sides?

 

These photo,s are what I have now of the xmember to frame position.
The xmember is bolted in the same holes it always was but it seems that the trans is higher too bad I don't have photo of position of the trans and the floor how it was before the frame off.

 

Do you have any pictures of the front side of the rear end?

- Eric

 

No not yet only this one from behind.

 

Is the driveshaft evenly spaced in the driveshaft tunnel the angle accents it but it looks like there is alot of room from drivers side of the tunnel to the driveshaft and less space on the passenger side

is the body centered on the frame

 

I'm wondering if you could drop your Xmember and bend it down a bit and then put it back up? You may have drop the exhaust a tiny bit. Everything looks as it should.

What motor mounts and brackets are you using?

 

did you change any floor parts sheet metal, braces etc? hey if the mechanical end is definitely ok and these are possibly aftermarket floors? massage it i had to massage acording to instructions a gear vendors overdrive small bump in my aftermarket floors. this seems stupid if all else is what i stated use a hammer!

 

If it's sitting low in the rear, this'll happen. But in looking at the pictures, that floor seems to have been repaired, judgeing from all the undercoating everywhere.
I'd try putting a straight 4x4 in the trans tunnel to check for straightness, [after removing the driveshaft] and if bent, use a floor jack to straighten accordingly.
Were the replacement body mounts as thick as the old ones?
Did you lower the rear of the car?

 

I used engine mounts P/N:2261 and the trans mount is P/N:2378 Auto extra.
The car is lowered with a complete set from Summit about 1 inch drop and the body was sagging too one side before and all body mounts where shot, the new mount where higher.
Did align the body back so the rockers have the same clearance again.
Did also replaced the rusted through rear lower arms for tubular ones from Umi.

 

Take the back-end up a couple of inches and forgetaboutit!!

 

Did you check to be certain that these were exactly the same length as the originals?

- Eric

 

The issue is not the rear end, it's the distance of the trans tail shaft to the floor. It needs to be lower, or the front of the engine needs to be higher. Are you running a radiator shroud? How is the fan position in the shroud?

 

Did not have a shroud and still has non but it looks like top of the fan clutch is closer to the radiator than the bottom.
Does someone know the correct height a th350 mount?

 

Did you mix match BB and SB mounts? In other words did the frame have the metal stands for a SB and did you use the rubber mounts for a BB attached to the engine? I believe if you mix and match BB & SM mounts like this you will run into this problem.

 

I now have a 403 smallblock with the SBO frame mounts that where on the car with motor mounts 2261 and 2378 trans mount.

 

I see from the one pic that the rear of the shafts hitting the rear floor brace. Your rears too low and maybe those new tubular control arms altered the pinion angle from its stock 3-4* downward or negative angle
It has to be one of these things:
1. Wrong pinion angle
2. Rear end is in the weeds too far (or both 1 & 2).
3. Floors were altered, doubtful.
4. Wrong drive shaft diameter, though it looks ok.
5. Wrong miss-matched motor/trans mounts, but they do look ok.
6. Or a combo of any of these?
When you installed the rear control arms did it alter the pinion angle? If the nose of the rear end is pointing level or up at the floor then this could be it? It should be 3-4* downward from horizontal (3* down for Polly bushings). If the pinions off as well as the drop in ride height I’ll bet that is the problem?

 

Your mounts are all correct. The T350 mount is the same as the T400 trans mount. The only other think would be to shim the motor mounts up. But if you massaged the floor, and everything clears, I would not even worry about it.

Rear pinion angle is not going to effect the position of the trans yoke. Lowering the vehicle by shortening the springs will not effect it either. Again IMHO the only things that will cause this issue are the space of the body to frame, the trans xmember or trans mount being to high, or the front of the engine too low.

 

It was stated that the top of the fan was closer to the rad than the bottom of the fan. The transmission mounts are supposed to be the right ones as are the engine mounts, but why is the front of the engine tilted down? Sorry I don't have a solution. (I would be leaning towards trying different transmission mounts.)

 

I did not check if the pinion angle is downward I will do that but then there should be no problem at the trans side like oldcutlass wrote.
The only thing I can think off is that crossmember or the frame was bent it is an open frame and not that solid, that,s why I replaced the lower arms they where getting thin.
I ordered and other brand trans mount and let the one I have modified to lower the trans yoke and test drive it because after I massaged the floor it hit the floor brace when going down a speed bump.
When I build up the frame with the engine in it the shaft was pretty close to the exhaust so I thought that would be an issue but it's closer to the floor then the exhaust.
Still wonder what went wrong?