Replacing HT-740 Pan Gasket

Glennman · November 24, 2019, 09:30:18 PM

I have a pin hole in my transmission pan, so I plan to remove it for repair. It is right on the corner where it had gotten scraped on the ground, and now it leaks, but very slow.

While I have the pan off, what else should I take the opportunity to replace inside the transmission? Will I be exposing screens, filters, etc? I plan to order the gasket from Luke with US Coach.

Thanks all,
Glennman

luvrbus · November 25, 2019, 06:29:54 AM

How you planning on doing the repair some of those pans for the 740 you cannot weld a pin hole or they keep cracking from the heat BTDT,if the fill tube has a pressed in adapter on the pan they won't take a weld if it is welded on they will

Bill Gerrie · November 25, 2019, 07:23:11 AM

Could you braze over the pin hole? I have sealed up holes in steel doing this and no issues.

luvrbus · November 25, 2019, 07:54:04 AM

Quote from: Bill Gerrie on November 25, 2019, 07:23:11 AM
Could you braze over the pin hole? I have sealed up holes in steel doing this and no issues.

I used brass and silver solder on Rico's 740 pan and every time it cooled down you could hear it crack

so I just changed the pan after fighting it for 3 hours, he may get lucky though

chessie4905 · November 25, 2019, 10:49:25 AM

Sandblast area. JB weld on inside and out.

David Anderson · November 25, 2019, 01:30:37 PM

Quote from: chessie4905 on November 25, 2019, 10:49:25 AM
Sandblast area. JB weld on inside and out.

Ah JB Weld, almost as important as duct tape. Should be in every tool box

It is some pretty useful stuff, for sure.

DoubleEagle · November 25, 2019, 02:50:34 PM

JB Weld might hold, but then, just how lucky do you feel? Listen to Cliff, get a pan. Sandblasting will create a rough surface to bond to, but it will also reduce the thickness of the pan. When the heat and trans fluid finally get to the JB, there goes even more fluid just when you need to climb a mountain. I successfully repaired an air tank with JB decades ago (I was young and foolish then), but leaking air does not do as much damage as loosing trans fluid. There is a low air warning buzzer, but is there a low trans fluid buzzer?

chessie4905 · November 25, 2019, 05:45:06 PM

If cleaned and done properly, it'll hold. The JB Weld will end up being thicker than the pan thickness. This stuff has sucessfully been used in millions of applications, more demanding than pinhole leak in a transmission pan.

DoubleEagle · November 25, 2019, 08:11:06 PM

That could be, but another reason for getting a new (or used) pan is that it's an opportunity to change the capacity of the pan to a larger size. They had a number of different sizes on the HT740. If he uses JB, I hope he gives us a report of how it went every two years.

Glennman · November 25, 2019, 09:35:33 PM

I've thought about using JB Weld on it. The pan appears to be aluminum. Lots of issues with cracking while brazing, etc. I'll look into finding another pan for a while, but once I have it off, I'll figure out a fix if I'm unable to find one. I'll check with Luke to see if he has one. I've worked with metals for years. I should be able to devise a fix.

One thing I never thought of until reading these responses is going with a larger pan. Wouldn't that just make it closer to the ground? Still, that is an intriguing idea.

Once I get started, I'll post my experiences. Thanks all... Glennman

sledhead · November 26, 2019, 05:28:35 AM

when I have used jb weld I clean the area with a boot type brush and use lacquer thinners on it two or three times with a clean rag each time . I find this way the lacquer thinner strips any grime or grease off of what I want to redo

dave

chessie4905 · November 26, 2019, 06:52:44 AM

Same here. Also use it for last cleaning before using silicone gasket sealer, and for that matter any sealer or gaskets. Got into that habit when re-sealing valve covers on GM 5.7 and 6.2 diesels. 5.7s were a bitch to get a good seal because of the normal crankcase pressure or blow by.

luvrbus · November 26, 2019, 07:51:38 AM

Quote from: Glennman on November 25, 2019, 09:35:33 PM
I've thought about using JB Weld on it. The pan appears to be aluminum. Lots of issues with cracking while brazing, etc. I'll look into finding another pan for a while, but once I have it off, I'll figure out a fix if I'm unable to find one. I'll check with Luke to see if he has one. I've worked with metals for years. I should be able to devise a fix.

One thing I never thought of until reading these responses is going with a larger pan. Wouldn't that just make it closer to the ground? Still, that is an intriguing idea.

Once I get started, I'll post my experiences. Thanks all... Glennman

The pan is metal on a 740 they come in 5,6,7 and 8 inch depths changing the depth you also need to change the depth of the pickup tube and screen plus adjust the dip stick it is easier to use the same depth pan when replacing it .Untied Transmission in CA has used pans so does Global in Tucson AZ a new one if you can find one are over $500.00.Me personally I would forget about JB Weld for a permeant repair

Van · November 26, 2019, 08:42:09 AM

When dropping the pan be sure to check for any chunks or pieces that might indicate some issues. Checking my records from a few weeks ago from W.W. the kit will cost you $136.42.W.W. Part #29530564 kit-filter which includes the filter, O-ring and pan gasket for a 7" pan. Have the serial #'s handy when ordering through them (W.W.). If there is nothing in the pan re-assemble and run it. Hint (stomp-stomp) be sure to chase the pan bolt threads with a tap and do not over tighten the pan bolts, they break easily

.

luvrbus · November 26, 2019, 08:56:21 AM

LOL and buy 10 gals of fluid I use 15/40 engine oil ,synthetic fluids are great but a waste of money in the old HT 740 transmissions IMO