Monthly Archives: August 2012

DIY: G50 Transmission Cooler/Filter Install

As you probably know by now, I am a G50 fanatic. I hate to see these cars scrapped because the owner did not do the required maintenance, even more so when money was spent on mods instead. I am guilty of this as well. As you may recall my ’90 Q met it’s fate a couple years ago because I failed to give the transmission the proper attention (in my defense I had the parts and was preparing to install). The transmission cooling on this chassis is insufficient from the factory, particularly on ’90-’93 models, so it’s a good idea to do preventive maintenance regardless of the year.

Let’s start with a little back story. The OG stable has acquired a new resident, a black beauty of a ’95 Q45, after the shop steed was hydroplaned into a barrier wall (everyone is OK, thanks for the concern). A new project was most definitely not in the plans, but this car was purchased out of necessity. If anyone is thinking about getting into a G50 in the near future it may benefit you to wait a couple months, as this car will be for sale.

Because this car is my current commuter it is a must that it be dependable. The last thing I need is another 2 ton paperweight; so one of the first items of business was a BG tranny flush, followed by the install of an external cooler along with an external filter. I had these parts already, but during the process of planning I discovered that the kits (purchased separately) had different size fittings. I opted to stick with the 5/16″ barbs and 3/8″  hose setup that came with the cooler, which required me ordering a couple hard to find fittings (3x 5/16″ barb tee, 2x 5/16″ barb to 1/2″ MPT) and having them overnighted.

Now there are some DIYs out there, but anything that starts off with “start slashing lines” can’t be taken too seriously IMO. This is how I did it.

First things first was mounting the cooler. According to the literature that came with the cooler in order to get 100% efficiency the cooler must be installed in front of the AC condenser. That wasn’t happening, so I opted for the 60% efficient location between the condenser and radiator. After messing around with the radiator zip ties I decided to mount the cooler directly to the radiator using self tapping screws (1 existing hole, 1 OG made). Before permanently mounting the cooler I attached 4′ of transmission cooler hose to each inlet/outlet and fed it out the bottom (I purchased 25′ and used about half).

The external filter was mounted to an existing hole in the frame rail with a bolt, washer, and lock washer. The car will be lowered therefore the fender liners will not be replaced, making this an easily accessible location that is well protected. When I got farther along I realized the aftermarket filter was similar in design to the OEM external filter (’94-’96 unless retrofitted, deleted) so I felt good about my choice vs. the more popular Magnefine.

Now here’s the part where intelligence, as well as a little common sense, comes into play. There seems to be some uncertainty in the community as to the direction of flow in the system. For the record; the fluid flows out of the transmission, into the filter, splits parallel to dual coolers, then merges back together and flows back into the transmission. The B&M instructions require the external cooler to be added after the OEM coolers. Here is how the new setup flows: out of the transmission, into the B&M filter, teed into the OEM lines where the external filter used to be, into the inlets (lower pair) of the OEM coolers, out of the outlets (upper pair), teed into the inlet of the B&M cooler, then teed out of the outlet of the aftermarket cooler and back into the dual inlets to the transmission. It sounds complicated but if you get under there and trace the flow it will make sense. In the end no OEM lines were cut, only 1 was deleted along with the OEM external filter.

Expect the entire project to take a few hours, no special tools required. At this point, if you’re like me, you will never want to see another hose clamp in your life.