Front diff punching hole in oil pan

Front diff punching hole in oil pan

Postby Tegnus [OP] » September 11th 2020, 1:55am

I have a 2004 Chevy Astro AWD and I had an issue where my engine mounts basically melted... More on it here: https://www.astrosafari.com/viewtopic.p ... 0#p1560286

Anyhow I though that problem was with the mounts dropping engine too low and that caused the hole:
Image

So I patched it with jb weld and though that all is good.
Image

BUT it appears that issues still persists as diff is still punching my JB weld away and the hole is back...

I am thinking that issue might be with front diff bushings, I understand that there are 4 of them and they all appear the same - are they?
Rockauto has no stock, but this is what I found: https://www.rockauto.com/en/moreinfo.ph ... 1&jsn=1421

I also can't figure if other places have stock as some that indicate status show discontinued, and some show nothing...

Is there anything I am missing that would cause this issue, except for those 4 bushings and transmission mount are there any other parts affecting this?
Also any suggestions for alternate parts just in case I can't find OEM?


Also will probably replace transmission mount as that has probably been shot too, why wouldn't it if everything else is not looking great... :banana:
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Re: Front diff punching hole in oil pan

Postby MechBob » September 11th 2020, 5:02pm

Looks like you have a motor mount problem,or trans mount has been shimmed up,forcing front of engine down,or something is really bent.
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Re: Front diff punching hole in oil pan

Postby Tegnus [OP] » September 11th 2020, 7:47pm

MechBob wrote:Looks like you have a motor mount problem,or trans mount has been shimmed up,forcing front of engine down,or something is really bent.

So you think it has nothing to do with front diff bushings?
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Re: Front diff punching hole in oil pan

Postby Mmusicman » September 11th 2020, 8:35pm

When my mounts were shot... my oil pan was rubbing on the differential axle tube.
But I don't recall seeing any interference with differential bushings or bolts.
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Re: Front diff punching hole in oil pan

Postby MechBob » September 11th 2020, 9:15pm

The front diff is in bushings,in frame mounts-2 on the left side.If the bushings were that bad,the diff would jump up and down,and make horrible noises.I would get it looked at by a good shop.
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Re: Front diff punching hole in oil pan

Postby Tegnus [OP] » September 12th 2020, 2:17am

Mmusicman wrote:When my mounts were shot... my oil pan was rubbing on the differential axle tube.
But I don't recall seeing any interference with differential bushings or bolts.

Yup that was happened too, and from what I can tell after changing melted energy suspension mounts that's not happening anymore.

But it also did rub out a hole in pan, and it's still taking out jb weld even if I re-apply it.
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Re: Front diff punching hole in oil pan

Postby MechBob » September 12th 2020, 2:58am

I will delve on this a bit more.Astros and S10/blazer deviants, have had this issue for years,mounts die, oil pan rests on axle tube,sometimes oil pan gets rubbed through.Many websites, you can research it.As we all know, original mounts for a AWD no longer exist.The "inserts(urethane) are generic,and fit many models of GM vehicles.For some years,Prothane Astro mounts were only for 2WD, whereas Energy Suspension sold different mounts,for AWD.Energy Suspension parts were/are made by Prothane.They might even be the same company,now.We do know factory,and Prothane 2WD mounts were 1/2" lower than AWD factory mounts, which is probably why Prothane never sold AWD mounts,but ES did.(the same in 2WD vs AWD s10 stuff).I noticed doing internet searches for ES, or Prothane, they started coming up with the same part numbers.Did Prothane absorb ES, and the crossover is leading to wrong part numbers/dimensions? I do not know,just throwing this out there.I will also say I crawled under my 96 astro AWD,in the gravel, it has well over 200k, original engine mounts.and the distance from the oil pan to the "black" steel tube that is the right axle carrier, is 3/4" or a bit more.And,the distance of the pan from the axle tube to the bolt(in your pictures,that holds on the right axle tube) is at least 3/4". Food for thought.I also could tell you about .All aftermarket motor mounts for Astro vans are now back to using the same mounts that fit S10's, 1/2 and larger pickup trucks,again.Is because they are old.They work,they just might not work properly.or for a long time.But,in your case, seems might be something else going on.
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Re: Front diff punching hole in oil pan

Postby SportsBoy » September 15th 2020, 12:20am

I'm pretty sure this is a poly replacement for the diff bushings -
https://www.amazon.com/gp/product/B000CNAXAW/ref=ox_sc_saved_title_2?smid=ATVPDKIKX0DER&psc=1
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Re: Front diff punching hole in oil pan

Postby Tegnus [OP] » September 21st 2020, 7:53pm

MechBob wrote:I will delve on this a bit more.Astros and S10/blazer deviants, have had this issue for years,mounts die, oil pan rests on axle tube,sometimes oil pan gets rubbed through.Many websites, you can research it.As we all know, original mounts for a AWD no longer exist.The "inserts(urethane) are generic,and fit many models of GM vehicles.For some years,Prothane Astro mounts were only for 2WD, whereas Energy Suspension sold different mounts,for AWD.Energy Suspension parts were/are made by Prothane.They might even be the same company,now.We do know factory,and Prothane 2WD mounts were 1/2" lower than AWD factory mounts, which is probably why Prothane never sold AWD mounts,but ES did.(the same in 2WD vs AWD s10 stuff).I noticed doing internet searches for ES, or Prothane, they started coming up with the same part numbers.Did Prothane absorb ES, and the crossover is leading to wrong part numbers/dimensions? I do not know,just throwing this out there.I will also say I crawled under my 96 astro AWD,in the gravel, it has well over 200k, original engine mounts.and the distance from the oil pan to the "black" steel tube that is the right axle carrier, is 3/4" or a bit more.And,the distance of the pan from the axle tube to the bolt(in your pictures,that holds on the right axle tube) is at least 3/4". Food for thought.I also could tell you about .All aftermarket motor mounts for Astro vans are now back to using the same mounts that fit S10's, 1/2 and larger pickup trucks,again.Is because they are old.They work,they just might not work properly.or for a long time.But,in your case, seems might be something else going on.

Thank you for background info. I have had poly engine bushings (same p/n) for ~6-7 years, but for whatever reason they only broke trough oil pan this year. I assume they might have been hitting oil pan before, but as mounts melted (catalytic converter failed last year), they dropped even more and that little bit was enough to rub out hole and JB weld is not strong enough to withstand occasional hit from diff, where oil pan without holes would be ok.

I have source original diff bushings, will probably swap out oil pan for a new/used without holes and change transmission mount and see if that makes any difference. Will probably know that at the end of winter as this is most likely not a project I'll take on this year. I have Tacoma as "daily" (weekend) driver so it kind of fill hole especially now when long term camping season is coming closer to end and I can do couple nights easily in tent.
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Re: Front diff punching hole in oil pan

Postby Tegnus [OP] » January 11th 2021, 10:40pm

So I went ahead and swapped out oil pan and transmission mount mid-December and went for a 1200 mile/2000km test drive/Christmas camping trip to Rockies. Had a great time and after returning home decided to look underneath - looking good so far. We didn't do any 4x4 action really, barely left pavement - lots of snow up there so not much FSR exploring, but yeah, I am happy there isn't a new hole in engine and hopefully this lasts at least another 5-7 years (if we still have Astrid by then).

Image

As you can see it's still touched oil pan, but at least oil pan is not leaning on diff all the time, which happened before the last hole occurred.
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Re: Front diff punching hole in oil pan

Postby markmitchmarkmitch is online! » January 19th 2021, 3:36am

when I built my V8 AWD set up I installed these between the frame and the frame mounts and also added a home made spacer under the transmission/transfer mount. I added poly for the frame mount as well as for the front differential mounts. I now have 1 inch between the engine oil pan and the front differential. If you need the part numbers and such for any of this stuff feel free to pm me and I will go through my records and get the info for you. Mark
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Re: Front diff punching hole in oil pan

Postby cowgirlcullen » February 23rd 2021, 12:34am

markmitch wrote:when I built my V8 AWD set up I installed these between the frame and the frame mounts and also added a home made spacer under the transmission/transfer mount. I added poly for the frame mount as well as for the front differential mounts. I now have 1 inch between the engine oil pan and the front differential. If you need the part numbers and such for any of this stuff feel free to pm me and I will go through my records and get the info for you. Mark


Mark, this info would be super helpful! I just called JTR to grab a modified oil pan and motor mounts to do my V8 swap and found out it won't work because my 400 cubic inch engine is Pre-1986. So back to the drawing board!

No idea how I'm going to overcome all of this - V8 swap + AWD + 2 piece rear main engine, seems like a lot to figure out, in addition to all the other stuff. Losing heart. :(

I didn't want to raise the engine 2 inches and stick with the stock oil pan because I feel like that would just throw so many things out of alignment and cause stresses and problems and probably add a laundry list of stuff to adjust. That may be my only option now though, not sure. JTR does sell an extention piece to modify the oil pan myself, but he said that won't work either.

I wonder if there's a way to fabricate some motor mounts that would accommodate both the V8 conversion and the 2 inch engine lift.
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Re: Front diff punching hole in oil pan

Postby markmitchmarkmitch is online! » February 23rd 2021, 1:29am

you do not have to lift it that high, I bought these and cut the slotted section off . Then I got longer bolts to put the triangle first then the frame side of the motor mounts then bolted it to the frame. Then use the mounts on the engine from JTR and this together gave me 1 inch of clearance. However I installed poly motor mounts and the differential bushing on mine were toast so I replaced them with poly also.

https://www.summitracing.com/parts/ptp- ... ukQAvD_BwE

https://www.summitracing.com/parts/ens- ... LUQAvD_BwE
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