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I have a crack in my 1988 S4 5spd transmission case. Apparently the crack was patched using a compound like JB Weld or something, and the leak has re-emereded. Unfortunately this was not identified by the two PPI's I had done.
So now I am trying to figure out what to do. I understand my options would be:
1. Re-patch: drain, clean oil out, and re-patch.
2. Weld case and rebuild transmission.
3. Replace transmission with unit a rebuilt unit
4. Replace case and rebuild transmission - which MY cases are compatible?
I sure would appreciate your input on what to do, if anyone has some vendors or spares that could be used would be greatly appreciated.
Thinking it depends on what's under that glob (patch), is it a hole or a crack?
How would this impact the repair? Is one more difficult to weld? I would think either would require a bead of weld. If a crack I suppose there is a need to terminate the crack with drilling a small hole.
Right, just saying if it's cracked then weld up the crack and grind it down, verses making up a patch to fill in a hole and welding all that.
Not that it can't be done, just more time and effort and depending on the hole how will it look.
If it was mine, I'd drain it let it sit, see what you have to work with, take some pic's of the damage, clean it up w/ brake cleaner, mix up some JB Weld and reseal it.
Start pricing your options, including swapping the case w/ used one from 928 International.
The metal gas tank epoxy repair kits sold at auto parts stores might work , special resins to be gasoline proof.....just seems a shame to pull the trans/rebuild for a small leak.
Transmission cases are made from a high grade of aluminum. Pretty simple to weld, however all of the gearoil must be removed....even the stuff in the crack to weld.
Talk to whoever is going to weld it. They may want it apart to clean the crack out, or they may think that removing, draining, flipping it over, and cleaning the crack is enough.
I don't think I'd trust anyone that thinks they can weld it, in place, with gear oil runnimg out the crack. If that was my only option....use some epoxy.
Thanks for all the super useful information everyone. I spoke with Mark Anderson of 928 International and he gave me some good advice. Any repairs I can do with the transmission in the car is going to be the most practical, he suggested welding or re-patching.
So that is were I am going to focus my attentions. Welding seems like the most permanent repair if I can find a place to do it. I called a radiator repair place and a transmission repair place and both would not do the repair 'in car' they sited concerns about oil contaminant or difficulty connecting electrodes for TIG. Should I be looking for a automotive specialty welder?
With regards to rematching, I have been researching patch products and came across this Hi-Temp aluminum patch from Permatex. Thoughts or opinions of patch products are appreciated. http://www.permatex.com/documents/TD...tive/31372.pdf
Beyond that, I would be looking at removing the transmission, and the case so it can be welded on a bench. I am going to assume the is the most economical option since cases are about $1800, and a rebuild would also be about that price. Potentially I could ship the unit of for both at the same time.
A crack that's weeping oil will continue to weep oil so long as the gearbox is upright and there's oil in it. So start by getting the oil out, and clear the area above the crack of oil if you aren't going to take the gearbox out. Then flush the oil that's in the crack out, using solvents and ultimately some brake cleaner. Until you are willing to put your sandwich in there. You'll do the same prep for a good epoxy repair as you would for a weld repair, making a small groove that you can fill with epoxy. Clean it again thoroughly before you epoxy.
The "patch" that's visible now looks like someone just smeared some epoxy over the crack rather than trying to repair it. There are some epoxy products that might be OK for that, but they are different from what you'd use for a repair. A surface band-aid patch needs to remain flexible, or it's just a matter of time before it weakens and leaks again. A good bond needs the surface roughened, and must be surgically clean.
I've seen some real artisan work done on aluminum cases both with epoxy and with the TIG torch. The welded solution is generally more secure if done correctly.
I have had trans cases and engine oil pans welded in place on the car. Porsche trans cases are made with good aluminum, very easy to weld.
You need to find a very good TIG welder. Drain all the oil, get a couple of cans of GOOD brake cleaner and flush the oil out of the crack. Use compressed air to blow the crack clean. Repeat - spray break clean, blast with air . . repeat as often as necessary until clean.
Blow dry, and blow air into the trans case to flush out all brake cleaner fumes. Then it should be weldable. Start at the ends of the crack and weld towards the center. Don't be afraid to lay a heavy bead. If necessary to make a second pass, let the case cool for a while first.
Last edited by GUMBALL; 03-29-2016 at 12:28 AM.
Reason: left out details
A crack that's weeping oil will continue to weep oil so long as the gearbox is upright and there's oil in it. So start by getting the oil out, and clear the area above the crack of oil if you aren't going to take the gearbox out. Then flush the oil that's in the crack out, using solvents and ultimately some brake cleaner. Until you are willing to put your sandwich in there. You'll do the same prep for a good epoxy repair as you would for a weld repair, making a small groove that you can fill with epoxy. Clean it again thoroughly before you epoxy.
The "patch" that's visible now looks like someone just smeared some epoxy over the crack rather than trying to repair it. There are some epoxy products that might be OK for that, but they are different from what you'd use for a repair. A surface band-aid patch needs to remain flexible, or it's just a matter of time before it weakens and leaks again. A good bond needs the surface roughened, and must be surgically clean.
I've seen some real artisan work done on aluminum cases both with epoxy and with the TIG torch. The welded solution is generally more secure if done correctly.
Great info, can you recommend some good patching products that you have used or seen used?
I have had trans cases and engine oil pans welded in place on the car. Porsche trans cases are made with good aluminum, very easy to weld.
You need to find a very good TIG welder. Drain all the oil, get a couple of cans of GOOD brake cleaner and flush the oil out of the crack. Use compressed air to blow the crack clean. Repeat - spray break clean, blast with air . . repeat as often as necessary until clean.
Blow dry, and blow air into the trans case to flush out all brake cleaner fumes. Then it should be weldable. Start at the ends of the crack and weld towards the center. Don't be afraid to lay a heavy bead. If necessary to make a second pass, let the case cool for a while first.
interesting where it cracked. id like to see under it. if the trans is drained, and the crack is SUPER cleaned, id use high powered blasts of brake clean and allowed to dry, i could TIG it in place... but again.. SUPER clean. as Greg said, the case metal is a nice high quality metal, melts like butter with plasma.....
Last edited by Ducman82; 03-29-2016 at 12:43 AM.
Reason: Gumball beat me to it
03-28-2016, 02:34 PM
Cracked Maunal Transmission Case - Need solutions
