Diff Mount Bolts Stuck

[Joe L.]

Re: Diff Mount Bolts Stuck

Well...all I can say is that the reinforcing plate remains very thick. I looked at the photo again and believe it looks worse than it is. The key here is get those bolts out, get the rust treated and go from there. Would be willing to bet that when I get to that point if I measure the thickness it will be darn close to any well survived example. As an engineer I am not worried based on what I can observe at this point. To answer you question this was a MA car from birth through 2000 and since then it has been off the road and garaged. Several knowledgeable folks including some of our very own NCRS have seen this car and commented on the relatively very good condition of the frame. Back in 1998 a local mechanic stated he could not adjust the trailing arms as one of the pivot bolts was frozen. I got it out. PB and patience. Same should prevail..eventually...with these two bolts. Another thing I did today in addition to liberal application of Kroil is gave the mount a few good whacks from various angles. That should help provide some shock to the bolts.

Keith-------


I have no doubt that the bracket is serviceable. As you mention, these plates are quite thick and even with the corrosion induced loss of material, there's still plenty left. As a matter of fact, the brackets used on 1963-E65 Corvettes had no reinforcements, at all. For L65-68 the bracket included welded-on washers to act as reinforcement. The plates were added for 1969 and later. The purpose of the reinforcing washers and plates was to help prevent elongation of the bolt holes. The original 1963-E65 brackets suffered from this problem. The welded-on washers helped but did not cure the problem. So, the thick plates were finally added for 1969 and later. Even these can suffer from bolt hole elongation, though, especially if the car is driven hard.

The type of corrosion I see on the reinforcement in your photo is salt-induced and not simply "surface rust". As I mentioned, I'm pretty sure that it's also the root of your bolt removal problem. You may find other chassis areas where this type of corrosion has "worked its wiles". Hopefully, these will be isolated and easily repaired. The fact that the car has lived its life in the northeast completely explains this. As I have said many times before, once salt-induced corrosion begins, it proceeds inexorably.

[Keith M.]

Re: Diff Mount Bolts Stuck

Tried CRC Freeze Off today. Still no love. So off to the Evaporust Spa for a bath it is!!

[Joe L.]

Re: Diff Mount Bolts Stuck

Tried CRC Freeze Off today. Still no love. So off to the Evaporust Spa for a bath it is!!

Keith-------


Are you saying that pounding on these bolts with a hammer while the differential is suitably supported will not dislodge them?

[Keith M.]

Re: Diff Mount Bolts Stuck

Keith-------


Are you saying that pounding on these bolts with a hammer while the differential is suitably supported will not dislodge them?

Correct. I sit on the diff to hold it in place. Put a sacrificial nut I bought on the end..screwed on far enough for all the nut to be on threads but not so far as to touch the reinforcing bar... so I can place an impact socket..free...not on tool..over the nut and pound away with a 5lb hammer. It laughs at me.

[Joe L.]

Re: Diff Mount Bolts Stuck

Correct. I sit on the diff to hold it in place. Put a sacrificial nut I bought on the end..screwed on far enough for all the nut to be on threads but not so far as to touch the reinforcing bar... so I can place an impact socket..free...not on tool..over the nut and pound away with a 5lb hammer. It laughs at me.

Keith------


The strange thing is that based on what I can see of the bolts, they do not appear to be corroded to any significant extent. So, the zinc or cad plating has protected them. It must be that some salt laden water has worked its way into the minuscule space between the bolts and the bracket/ carrier case. As I previously mentioned, once salt-induced corrosion begins, it proceeds inexorably. So, in this case and sight-unseen it's proceeded to an extreme degree.

[Thomas N.]

Re: Diff Mount Bolts Stuck

Careful with Evaporust and Cast Iron. You must completely immerse it, or else you will get an "etch line" where the level of evaporust ends. Some cast iron doesn't take to well with it. I'm a firm believer of Evaporust, but do not use it on cast iron. Those bolts when they get rusted in there need heat to break them loose. Evaporust doesn't really wick in there. I've heated the bolt heads and the casting area where the hole for the bolt is and used an impact to get it out.

[Keith M.]

Re: Diff Mount Bolts Stuck

Careful with Evaporust and Cast Iron. You must completely immerse it, or else you will get an "etch line" where the level of evaporust ends. Some cast iron doesn't take to well with it. I'm a firm believer of Evaporust, but do not use it on cast iron. Those bolts when they get rusted in there need heat to break them loose. Evaporust doesn't really wick in there. I've heated the bolt heads and the casting area where the hole for the bolt is and used an impact to get it out.

Thanks. Yeah I've seen the etching and not just on cast iron. In this situation I did not want to submerse the entire diff...and these parts will get refinished any way and further are not in a highly visible part of the car. I believe the bracket was/should be semi gloss black and the diff casing natural. And I am not overly optimistic on this bath. For bad parts I do a usually do a 2 day soak...but since I cannot submerse this entirely maybe will check it after one day. Seems the shank of these bolts are essentially rust welded inside the sleeves. We shall see.

Should I one day get to claim victory on this one...you are all invited over for a beer!!

Keith

[Keith M.]

Re: Diff Mount Bolts Stuck

This is getting to be a daily blog. So yesterday morning after almost 24 hours of Evaporust I pulled it out. First tried the nut/impact socket knocker method....nothing. I periodically unthread the nut to monitor things and upon doing so saw the bolt threads getting a bit unhappy so gonna cool it on that going forward. Nut still threads on and off but threads starting to get compromised. So next up put a socket on a breaker bar with a pipe extension...finally felt something give...unfortunately it was the socket splitting. First time for that for me. Better the socket than the bolt head I guess.

Sooo...please check my next plan of attack here.

1) Thinking it time to bring the heat but I rarely like to do that...I am not all that savvy on technique and worry about compromising hardening etc. I have propane and MAP. If I try that where is best to apply the heat? Bolt head? Bolt end? Bracket surrounding those? diff where the bolt goes through? All of the above?

2) Before trying heat was thinking that since the one bolt is getting a bit compromised and they might need replaced anyway....take a BEEG FH and wail away on the end of the bolt itself like no tomorrow. Its a dog end bolt so even if it flares it would still come out and likely still accept a nut...though would probably replace at that point.

3) And the last resort....diff is going to Gary R for rebuild anyway so send it all as is and let him sort it out!!

Thanks for any input.

[Thomas N.]

Re: Diff Mount Bolts Stuck

If you are going to have Gary rebuild the rearend, I'd leave it alone before you mushroom the bolts too much, and contact him. It would be best if he could take care of it. He has a Bridgeport and a real set of torches, that if needed, he could start to drill these out to help relieve some of the pressure, as a worst case if he can't use heat to remove it. He is competent, and will do you well.

P.S. I'm not implying that you are not capable, but if he is going to rebuild it anyways, he has more tools at his disposal to ensure success. The bolt is stuck in there enough to crack a socket, I'd hate to have you progress and crack the housing next and render things useless, especially if it is the original rear end for your car.

[Keith M.]

Re: Diff Mount Bolts Stuck

If you are going to have Gary rebuild the rearend, I'd leave it alone before you mushroom the bolts too much, and contact him. It would be best if he could take care of it. He has a Bridgeport and a real set of torches, that if needed, he could start to drill these out to help relieve some of the pressure, as a worst case if he can't use heat to remove it. He is competent, and will do you well.

P.S. I'm not implying that you are not capable, but if he is going to rebuild it anyways, he has more tools at his disposal to ensure success. The bolt is stuck in there enough to crack a socket, I'd hate to have you progress and crack the housing next and render things useless, especially if it is the original rear end for your car.

Some great advice. I just hate giving up! Yes original 3.70 posi

[Joe L.]

Re: Diff Mount Bolts Stuck

2) Before trying heat was thinking that since the one bolt is getting a bit compromised and they might need replaced anyway..

Keith------


While what can be seen of the bolts appears OK, the prospect that these bolts are going to be re-usable is dim, indeed.

[Keith M.]

Re: Diff Mount Bolts Stuck

Keith------


While what can be seen of the bolts appears OK, the prospect that these bolts are going to be re-usable is dim, indeed.

Indeed. I would NOT put money that they WILL be reusable. Time will tell. I have never been stymied before...and never cracked a socket...and though I believe I could prevail here... the cost would outweigh any benefit. I am sensing the bolt shafts are virtually welded in the slots. Gary will handle it and likely with ease.

On another note....I wanted to share that I believe the rust process does not ALWAYS proceed "inexorably". The rust process involves oxygen and iron. It is possible that the converted (rusted) iron on a piece could in effect create a barrier to any further oxygen getting to the underlying iron which would therefore retain it's unoxidized properties. Road salts...or other salts...accelerate the rust process by bringing free ions to the party and acting as an electrolyte. Having said ALL that....none of this really detracts from the intent of your comments in that the rusting process is one to be respected and avoided.
Regards,
Keith

[Leonard M.]

Re: Diff Mount Bolts Stuck

Keith, I can understand why you continue to try; I don't give up either. Watch these videos. This guy did a lot of work to show what works best on frozen bolts. Very entertaining!
Which Penetrating Oil is Best? Let's find out! - YouTube
Best Penetrating Oil? Seafoam vs Gibbs vs Liquid Wrench - YouTube

[Tim S.]

Re: Diff Mount Bolts Stuck

Have you given any though to welding the a nut on to the threaded portion of the bolt? Many exhaust shops use that method. I have used the method when removing broken bolts and studs. The quick rise in temp that goes through the bolt is often enough to bust the bond of rust. By the looks of the pic, you'd have enough room to then cut off the end of the bolt / nut to remove the rusted bolt from the diff.

[Jeffrey S.]

Re: Diff Mount Bolts Stuck

Just a thought. If you have access to a stick welder / strike an arc on the head of the bolt let the rod stick for a second or two / this will heat the entire bolt pretty much red hot and that should free it from it captor / the longer you hold the arc the hotter the bolt will get so be careful as you can melt the bolt . I have seen this approach work on what appeared to be impossible situations in the past . Hope this helps Jeff