Topic: Differential Cooler Discussion

[wspohn]

A clean rear end is good enough reason for me!  I hate it when my rear end is covered with black mist.

The oil on the outside of the diff may or may not be related to a heat issue.

It is common for a diff to puke out some oil when under hard use, whether or not it overheats. The simple breather they always install on a diff is an indication that the factories are aware of this tendency, but these breathers are often not optimally designed for really hard use - they are small 'pig tail' metal tubes intended to allow air out but hopefully not oil, or a short straight tube with a dust cap on the end.  The problem is that they are often not long enough to cope with the additional flow that energetic car use can result in and you get excess oil that comes out the top.

The solution can be as simple as connecting a plastic tube maybe 6" long that gives enough length for the oil to go up the tube a bit and then fall back into the diff without getting high enough to spew right out, or if you are really worried about it, lead the tube into a small catch bottle, usually in the trunk.

Coping with this sort of breathing issue and worrying about oil temperature are not necessarily related - even when there is zero heat issue, you can still have a leak issue, and fitting a cooler often just happens to solve the spewing issue as well by giving expanding oil a place to go other than out onto the diff case, but that doesn't mean that you have overheating.

I still suggest that you investigate exactly what conditions are before assuming that you need a cooler.

[Mihela816]

GM had a service bulletin for an updated diff breather with a longer tube for this exact reason.

[jlab8]

GM had a service bulletin for an updated diff breather with a longer tube for this exact reason.

Yes, and that TSB isn't really possible to complete as written, because the nipple left after popping the breather cap off is exceedingly short, and is topped with a large lip that makes creating a secure connection (with a hose clamp as directed in the TSB) is impossible. I had a replacement nipple machined (with a much longer external neck) from scratch and installed in its place.

Literally, the TSB directions are:
1. pry off old breather cap
2. throw that away.
3. hose clamp a replacement (same unit) breather to one end of a couple feet of hose.
4. hose clamp the other end to the nipple from the old breather, still on the diff.
5. zip tie the breather end somewhere higher, under the trunk area.

[jlab8]

This is what it looks like:

[Critterman]

depending which way that fan is facing it could give you or take away up to 5 hp!     Looks like it should get the job done.

[miller11386]

how did you wire the pump? just on when the car is on? or do you have it switched?

[jlab8]

It's a puller fan, and both it and the pump are wired to run when the ignition is on.
I opted for a gear pump typically used for circulating turbo oil in LSR motorcycles, and it's very quiet when running.

All the grunge on the differential is the old gear oil misting out of the original vent. I need to clean the underside of the car soon.

[spartan]

Jlab8, If you don't mind, what was the cost for parts and installation?  Who did your install?  Can you list out the parts?

[jlab8]

Parts, fabrication & install was $1500-1600 or so. I'd have to break out the calculator for the exact total, because I had a number of other items handled on the same invoice, including ceramic coating the exhaust system from the manifolds back. BlackTrax did the install.

The pump came from RB Racing, I used their "small" since the differential doesn't need any pressure and 2.0 GPM provided by that is still overkill, along with an inline micron oil filter. No drainback valve needed, as the gear pump doesn't need to be primed.
Various fittings and braided lines & hardware.
The cooler was just a normal off-the-shelf part.
All the bracketry had to be fabricated.
The suction line was connected to a bung welded into the side of the differential casing, as the GM book's design calling for use of a banjo fitting on the drain plug (while easier to install) is at much greater risk of road hazard damage.

I may go back later and install a switch for the fan, just because if I ever need to drive/park on gravel or dirt, it's going to make a dust cloud, but that really doesn't come up with this car.