I have a 72 Cutlass/442 with a 350 4bbl and th350 transmission. I just changed the leaking steel transmission pan to an aluminum pan from Summit.

The aluminum pan is thicker than the steel pan, probably because aluminum is a softer metal. The extra thickness of the aluminum pan has caused the 2 holes on that little linkage bracket thingy to not line up with the holes on the pan. As a result, I can't get two of the bolts back on.

I see two options here short of getting a new pan:

1. - use a dremmel tool to grind some of the pan off so that the bracket fits - no thanks.

2. Use a dremmel tool to grind off some of the bracket and possibly use a drill to make the holes on the bracket slightly larger to make it easier to line up the bracket holes and the pan holes.

Neither option is particularly appealing, but I think #2 is probably the best option.

Has anyone had this problem before?

Is that little bracket easily removed from the linkage to make modification of the bracket easier (so I don't have to dremmel it underneath the car)?

Any suggestions are much appreciated. Thanks.

I'll try to post a pic of the little bracket thingy I'm talking about later today.

 

Ground part of the bracket off using a dremmel. Took a couple hours, but it worked great.

Did the first pass on torquing the bolts to 5 ft. lbs. Everything good.

When I did the second pass to torque the bolts to 15 ft. lbs., two of the bolt holes sort of stripped out, I guess is the best way to describe it.

Clearly the threads on those two bolt holes must have already been stripped because I barely got past 5 ft. lbs of pressure and all of a sudden there was no more resistance coming from those two bolts.

The rest of the bolts torqued down to 15 ft. lbs. without any problems.

The stipped holes would explain why the PO put a sh!tload of RTV sealant on the transmission pan, even up into the bolt holes.

Does anyone know how I repair the stripped out bolt holes??

 

That they would.

Well, if it were me, I would just drill 'em out bigger, tap 'em, and use bigger bolts.
What are they, ¼-28? So thread 'em for 5/16-24 and be done with it.

If you want to get really fancy, go buy a HeliCoil kit for ¼-28, or whatever the original screws are, and HeliCoil it - that's the "right" way to do it.

- Eric

 

why not mark the location for the two bolt holes in the pan where they belong drill them out and have a welder fill in the old ones CAREFULLY grind them flush and wala. A+ helicoil

 

He could HeliCoil them without welding them up.

In fact, aside from the risk of destruction to the transmission case or the entire car (from fire) from welding, the holes would likely end up in the wrong places, whereas if you started with the existing holes, they'd be in just the right places.

I still say tap it out one size bigger (or, the next Metric size, which will be closer, and which is guaranteed to drive every subsequent owner homicidally insane until the end of time).

- Eric

 

I agree, Helicoil would be optimal.

But you can get a tap and die set for under 100 dollars and have it for life.

i've had mine for almost 10 years now and have tapped many holes. Heh.

But then again, going 5/16, you might pay under 10 bucks if you get the socket and tap itself.

 

I didnt meen weld the block i ment move the holes in the new pan then weld up the ones that dont line up,that way the bracket would have fit .I would never weld the block on the car.Tooooooo much work.

 

If you want to get really fancy, go buy a HeliCoil kit for ¼-28, or whatever the original screws are, and HeliCoil it - that's the "right" way to do it.

- Eric[/QUOTE]

Thanks Eric.

I think I'll do it the "right" way and HeliCoil it so that I can use the original bolts and the same size bolts all the way around.

I researched the helicoil kits, but there are ALOT of them. I don't understand how to pick the right one.

The pan bolts are hex bolts that use a 6mm hex (allen wrench) to tighten them. I believe the length was 1 inch. So does that mean that I would buy a 6mm x 1" helicoil kit?? I'm not sure how to determine whether the threads are fine, extra-fine, or some other type.

Do I have to buy a special type of helicoil kit because the trans housing is aluminium?

 

You just need to get a kit for the size thread that you want.

Okay, this seems weird.
I double checked, and it looks like the original screws are 5/16-18 with a 1/2" hex head, 0.6" long, for both TH350 and TH400.
They are NOT socket head screws, they are NOT 1" long, and it is unusual to find fasteners with American threads, but Metric heads.
If you were trying to screw metric screws into American holes, that would explain your problem.
Now, it may be that I'm unaware of some sort of aftermarket screw kit that's out there, but I only know what I know.

No. They're all stainless steel.

Based on what I've read (sorry, I'm not crawling under the car in a blizzard to remove a trans. pan screw to measure it), these screws are 5/16-18 and just over 1/2" long. This would mean that you want to get a HeliCoil kit for 5/16-18 threads about 1/2" deep. I believe that all or most of the holes are blind, but all of the HeliCoils I've seen have bottoming taps, so that shouldn't be a problem.
You just drill the hole, tap the thread, and screw in the insert. Seeing as how you're going into aluminum, it should cut like butter.

I would confirm, though, that the holes you've got are threaded for 5/16-18 before going any further.

- Eric

 

Yea, this was a JEGS aftermarket aluminum pan that I swaped for the original steel pan. The bolts that came with it have "allen wrench style" heads (I always called these "hex head"). A 6mm allen wrench fit them perfectly, much better than any of the standard allen wrench sizes. The threads on the replacement bolts were the exact same width as the original bolts, I checked them before putting them in.

The replacement bolts were almost an inch long, vs. the approx 1/2" length on the original bolts. The extra length is to compensate for the thicker pan edge on the aluminum pan and extra thickness added at the bolt holes. In any event, the replacement bolts will still only penetrate approx. 1/2" into the housing, so the helicoil should be 1/2" in length.

Dude, "snow storm." That sucks man. I won't tell you what the temp was here today. Ok, it was 78 and absolutely beautiful. Sorry.

In all seriousness, thank you for you help.

 

Okay, all the fastener stuff makes sense, then.

I'd HeliCoil them and be done with it .

- Eric

 

When I take the transmission pan off to do the heli coil, should I put a new pan gasket on? Thanks

 

yes ,unless you want to chance doing it again next week.

 

I finally did this today. Not difficult at all, just really really messy. Lots of spilled transmission fluid and lots of metal shavings. Finding the right helicoil kit was the hardest part.

For future reference, Eric was correct regarding the size of the helicoil inserts needed for the stock transmission pan bolts. 5/16-18. I got the kit itself from Orielly for about $15. I also bought a "tap wrench" for $11 from Orielly to make the job a little easier. To get the little "tang" out of the helicoil inserts after they were installed, I just used a drill-bit and a hammer. A couple love taps on the drilll bit and the tangs easily broke-off as they were supposed to.

Thanks for everyone's input.

 

A Helicoil, judiciously applied, can turn a very bad day into a moderately good one .

You're welcome!

- Eric