1930 DC 8: keeping the oil in the differential

My DC drips oil from the diff. I think it is coming along the thread on the bottom bolt. All the cover bolts have one end in the oil and one in the air - dumb idea.

How do you seal it to keep the oil in?

When I swapped the crown wheel and pinion about 15 years ago, I went to a great deal of trouble to first clean and then seal the bolt threads with Loctite Thread Seal. I got four years of clean floor then the flood gates cracked open and have gradually opened further since.

I was thinking of trying another clean and thread seal, this time with a soft washer under the bolt (something like a spark plug washer) as well. I suppose the steel must be spotless under the washer too, i.e. no paint or rust.

Help! Any experts out there?

Graham

Your idea of using copper washers under the bolt heads is a good one. The 9" Ford rear ends used copper washers under the nuts that held the differential into the housing. They work very well. Some cars have cylinder head studs that thread into water passages. They use sealer on those threads. You might be better off with the washers, you can always tighten them up. Are you sure that you gasket has not failed? I have just recently done my 29 DA rear end rebuild and thought that the oil was leaking through the threads. It turned out to be the gasket. Good luck, Terry

Thanks for your reply Terry. I had thought of copper washers, but there are two problems. Firstly, good paint over and around them is essential - otherwise they promote rust in steel nearby due to galvanic action. Secondly, tightening them up is not really very good because the diff cover is not very heavy. It just deforms under the bolt and squeezes the cork gasket out, making the leak worse. This is how it was before I tidied it up. I was thinking of something more crushable. Not sure what though; I even thought of those red fibre washers.

I have tried thread seal - PTFE tape to be precise. It didn't work. It works for water, but I have never had success with it for oil. That is why I used a cyanoacrylate thread sealant from Loctite.

I am fairly certain the leak is along the bolt threads. There is oil around the two bottom bolt heads and on top of the lip on the bottom of the diff cover - it couldn't be there if the leak was from the gasket, unless it was right at the bolts and came out at the bolt.

However, I was trying to be cheap. Probably, as you say, replacing the gasket and putting in new thread seal on clean threads would be the best, perhaps with soft washers too.

Thanks again.

Graham

G'day Graham,

We have a 1930 DeSoto Straight 8 (almost the same as the DC8) which doesn't leak diff oil down those bolts. When we did ours, we cut a new gasket and sealed it with locktite master gasket. I think we used the locktite tread sealer (can't think of the number), the white colored one in the white tube and 15 years later it is still fine.

You could also consider using GM thread sealant rather than the locktite, it is expensive but I have been using it on other projects more recently and been very impressed.

Do you have a photo of your DC8 you could share? I am currently very slowly rebuilding a DC8 Roadster with my brother and father.

Cheers

Stewart

Thanks Stewart. I used Marston Hylomar gasket goo on the cork. I'll try the loctite one. It sounds like I'll have to do the job properly. Again. Sigh!

Photo attached. Do you have one of yours? I saw the image you posted on my other thread and thought "right hand control, YAY" before I saw where you were from! We have one cabriolet in NZ and one "coupe" cut down DC sedan, plus a CF coupe, from memory. Mine is very early in the run: body SED 545.

Graham

G'day Graham,

The image in the other thread is actually of Dad's 1930 DeSoto CF8.

We have two cars, Dad has a CF8 Sedan which is on the road and we have a DC8 Roadster is is about 10% restored.

This is Dad's DeSoto

This is our roadster about 5 years ago, there has been little progress other than on the steel work.

Cheers

Stewart

Hi Graham, I just came across this post. From the body number your car is Canadian built. I have a Canadian built coupe. Do you happen to have a plate that looks like the one in the photo below on your firewall? If so can you read the text in the Dodge Brothers emblem?

regards,

David

Do you happen to have a plate that looks like the one in the photo below on your firewall? If so can you read the text in the Dodge Brothers emblem?

Hello David and Happy New Year, Maybe and no. There is a plate that shape high on the firewall RHS but it is almost all grey = paint (or transfer) free. I understand all RH control DBs were built in Canada. I think I read it somewhere in a book about DBs. My unreliable memory says 86 RH control were built. Regards Graham

Hi Graham, yes that is the location of the plate. Dodge Brothers Canada made both left and right hand drive cars for the local market and export, respectively. So far the only place other than North America where Canadian built cars have turned up is New Zealand. Dodge Brothers Canada built just under 1000 DC-8s. Dodge Brothers USA built right hand drive chasses and shipped them to Australia where Richards built composite bodies for them. They also exported right hand drive cars (eg to Australia, UK etc)

regards and thanks for looking at the plate

David

I use the copper washers (just in the bolts below fluid level) and cork gasket (original set up) it used to leak till I put the correct 600W oil back in, no leaks now. I like the idea of the plastic washers.

I use the copper washers (just in the bolts below fluid level) and cork gasket (original set up) it used to leak till I put the correct 600W oil back in, no leaks now. I like the idea of the plastic washers.

So originally it had a cork gasket. How thick? I was wondering about this, because one cannot tighten the bolts much without deforming the cover and squeezing the gasket out. I was wondering if a heavy paper (plus a cement with filler properties) would be better coz it won't squeeze out? I have spent a bit of time flattening the cover again. I have also seen a thick steel ring under the bolts to prevent distortion of the cover.

BTW, the leaking oil was coming from the gasket at the bottom over a length of about 100 mm - I was wrong, as is usually the case according to my wife. The bolts were all dry in the threads within the housing threads. And there was no oil left in the diff other than a little below the casing lip.

I suppose the other thing I must do is make sure the breather is clear. Presumably it is in the arrangement that holds the brake pipe to the diff. housing on one side.

Hi Graham,

So it is the cover plate at the back which is leaking? Rather than where the third member bolts into the housing?

I have always had great success using locktite master gasket with a paper gasket on damaged or uneven surfaces.

Cheers

Stewart

Yes, the pinion union is fine. How thick was your paper gasket Stewart? Basically brown paper?

Graham

Mine is made from a thick gasket paper like you can buy from most automotive suppliers, I think it is this one http://clampline.com.au/product/read/goss-gasket-paper/4238/ 1/16th of an inch or 1.5mm.

Cheers

Stewart

I plan on using silicone /RTV made for gearlube from Mopar instead of gaskets- Just like modern vehicles...I'll let you know if I have any troubles with this method...

Thanks for your input everyone. I have come to the conclusion that cleanliness must be rigorous with a good gap filling cement to take up the unevenness in the surfaces. So this is what I did...

After carefully scraping off old material, I have cleaned up the differential case face with petrol then acetone and ground off the lip at the bottom made when the crown wheel bolt broke and was rammed through the bottom of the cover. The cover was cleaned similarly and checked for flatness. Gasket is 1.6 mm rubberised cork with Loctite Gasket Master 518 and primer 7649. Thread seal 567 is on the bolts. Here's hoping for better than 4 years before the leaks this time.

Does the diff. have a breather? Can't see anything like that. Maybe it just breathes through the axle bearings and brake drum seal? i.e. what happens when it heat up and cools? I would expect other Dodges of similar years to be the same or very similar?

BTW, it looks like crown wheel bolts breaking and going through the cover is not uncommon in these vehicles. My spare was damaged in the same way and the one on my car had the same damage previously repaired when it happened to me. Conclusion: those locking tabs on the crown wheel bolts are unsatisfactory! Those on the spare and in the car were all in-place but all the bolts were loose on both crown wheels when one broke off. I used Unbrako bolts with Allen heads torqued to 50 ft.lbs with Loctite Super Stud Lock, all drilled and wired in pairs with Ni-chrome wire. So far so good.

Edited April 2, 2014 by Spinneyhill (see edit history)

What weight oil have you been using?

600W will help to minimize leaking too.

What weight oil have you been using?

600W will help to minimize leaking too.

Yes, heavy oil will not leak easily (unless it is in my steering box right beside the hot exhaust manifold). But for differential lubrication, I am dubious about such oils. The "600W" of old had no spec as far as I can see and was probably more like 150 or 200 cSt viscosity when cold, but when hot was probably pretty thin. It also foamed like billy-o and had poor wetting and lubricating properties. When something better came along (as early as 1932, designed for hypoid gears) they used it retrospectively, according to my reading. I have been using a naphtha oil (most mineral oil you buy is paraffin based) that does not foam and has the most amazing wetting and "stickability" properties.