Dumb move causes more transmission problems..

Beck · July 23, 2015, 11:26:38 AM

I was cleaning up some rough casting on my 350 turbo transmission case. On my little tractor the top of the transmission is exposed so I wanted it pretty. I was using an angle grinder with flapper disc. I cleaned up some rough spots on the top. Then I moved to the passenger side casting mark. All was good. I proceeded to the drivers side heavy casting parting line. I hit oil..... Crap.

I never saw a hole. 2 tiny spots started to weep. Does anyone know if that is a pressurized passage or just case oil at the casting line. The transmission has clean ATF in it, but the leakage appeared dirty/rusty. I wiped it down with solvent and there was no further leakage. Surely it wasn't impurities in the casting? I applied a JB Weld type product. Now what?

Choptop · July 24, 2015, 06:28:53 AM

Bummer. I don't think JB weld will hold there if under pressure.
If it were me, I'd have a donor case ready, just in case.
Could it just be oil that worked it's way into the case from the outside?

Crosley.In.AZ · July 24, 2015, 08:15:12 AM

I dont understand where the location is.

Oil pressure is at bottom of the case for most part. If you are talking the case cast line that runs on top of case.

Beck · July 24, 2015, 10:27:36 AM

Quote from: "Crosley"I dont understand where the location is.

Oil pressure is at bottom of the case for most part. If you are talking the case cast line that runs on top of case.

It is at the case cast line near the top. If you were looking at the transmission from the rear it would be at about the 10 to 11 o'clock position about 5 to 7 inches in front of the tail shaft mounting flange. There was a pretty good sized bump under the casting parting line. I was hoping there wasn't a pressure passage there.

I have already sealed it up. If not I would turn the case upside down and see if it leaked any more. The dirty color was obvious, not like the clean fluid in it. The leak was 2 tiny spots. It didn't flow out. I am hoping for casting impurities, but liquid in molten aluminum? No way.

I was going to upgrade it with a manual valve body and clutches. Now my plan is to run it as it is. If it leaks I don't have anything but time invested. If it has internal problems I can say "It was bad anyway" and do a complete replacement.

Originally I wasn't going to cover it (that was why I wanted it pretty). Now I'm considering a transmission blanket. I should have just gone with the blanket and left it rough. Hind sight....

Arnold · July 24, 2015, 11:27:27 AM

Quote from: "Beck"I was cleaning up some rough casting on my 350 turbo transmission case. On my little tractor the top of the transmission is exposed so I wanted it pretty. I was using an angle grinder with flapper disc. I cleaned up some rough spots on the top. Then I moved to the passenger side casting mark. All was good. I proceeded to the drivers side heavy casting parting line. I hit oil..... Crap.

I never saw a hole. 2 tiny spots started to weep. Does anyone know if that is a pressurized passage or just case oil at the casting line. The transmission has clean ATF in it, but the leakage appeared dirty/rusty. I wiped it down with solvent and there was no further leakage. Surely it wasn't impurities in the casting? I applied a JB Weld type product. Now what?

I had a very similar thing happen on my 1994 GM 30 Van in 2010 when it was 16 y/o.It developed a tiny drip..I never looked close..sure looked like a seal..wasn't anything that warranted looking at really closely..but I did anyway..I could not see that it was not weeping at the seal but through the case..
I let it drip a bit for awhile and figured at that time that the next time it was in for service they could do that too.

They showed me where the case was porous and out came the fluid

16 y/o work van starts leaking something

The worst part of it was when this mechanic really thoroughly cleaned that housing there and we found it to have enough cracks in it for him to say the truck is not safe to drive..from drip drip to unsafe did not take very long. He says he has seen these break..ugly..and he has seen core rot in pretty much every transmission casing..

Truck goes in for oil change and ends up with back half of transmission change

Crosley.In.AZ · July 24, 2015, 06:42:59 PM

Quote from: "Beck"

It is at the case cast line near the top. If you were looking at the transmission from the rear it would be at about the 10 to 11 o'clock position about 5 to 7 inches in front of the tail shaft mounting flange. There was a pretty good sized bump under the casting parting line. I was hoping there wasn't a pressure passage there..

ok. I thought you were further forward.

The area you describe is the low - reverse piston area. That sees high pressure in reverse and manual low (first gear). Round piston, in read of case. Last out, first in

We've had customers drill holes thru the car floor into the case in that area. The plug and bondo the case up. Send it back for warranty. Quickly : the warranty claim is denied!

Crosley.In.AZ · July 25, 2015, 12:06:59 PM

case area for rear piston

Beck · July 27, 2015, 10:13:28 PM

The red spots are where the case leaked after sanding. You can see it has been epoxied (JB Weld type), sanded and painted.

Crosley has been helping me out through PM's. THANKS!

I was gifted a 250-C transmission for parts. Unfortunately the case isn't what I need. BUT, I have located another 350 set up for a pulling truck. Unfortunately it is a 4x4 transmission. The 250-C output shaft might work in that. The 250-C output shaft is rifle drilled.

I have tentatively made a deal on that transmission, if it looks ok when I get there.

Crosley.In.AZ · July 27, 2015, 11:58:11 PM

Quote from: "Beck"The red spots are where the case leaked after sanding. You can see it has been epoxied (JB Weld type), sanded and painted.

Crosley has been helping me out through PM's. THANKS!

I was gifted a 250-C transmission for parts. Unfortunately the case isn't what I need. BUT, I have located another 350 set up for a pulling truck. Unfortunately it is a 4x4 transmission. The 250-C output shaft might work in that. The 250-C output shaft is rifle drilled.

I have tentatively made a deal on that transmission, if it looks ok when I get there.

Those are non pressurized areas. The odd looking lump on the case side, just in front of the round governor cover. Is the parking pawl location. It actually moves thru the low/reverse piston notch. No oil psi there

The light weight parts of a T-250C trans are good for Stock automatic drag race classes.

I've also used the parts in high RPM T-350 with aluminum planetary units. Small engines that spin north of 10k RPM

Lighter parts take less energy to accelerate , which I am sure you know already.

Check the T-250 output shaft for twist in the splines. No twist, run it like you stole it.

Smaller front planetary unit can be machined down, reduce weight. Add a torrington bearing in there between the ring gear and palnet.... Also torrington bearing on top of the ring gear where the FWD drum meets up.

Just random thoughts on stuff I do to race units

Beck · July 28, 2015, 10:18:01 PM

I talked to a local shop today, they will not build using any 250-C parts. They say they are too weak and breakage prone. They have a large supply of used 350 output shafts. Their charge was $75 to $100. That includes disassembly, inspection, reseal, and reassemble with the 2wd shaft. Again any other needed parts would be added. I have dealt with them before and was happy. It looks like they will get the job.