I am looking to add a transmission cooler to my stock (non-Z51) 08. My plan is to purchase a Z51 DeWitts radiator with the integrated transmission cooler and run factory lines to it. Is it true that the stock differential is cooled by the transmission so if I keep the transfluid cool I should stop overheating the differential fluid?

Can I add a cooler to the existing system? Does my transmission support it? Can I use the factory Z51 lines?
Any instructions on where the lines are installed if there is anything I need to do to fill the system? How much additional fluid does it take?

 

I'm kinda confused by what you're asking. Is the trans an A6 or M6? How do you know the differential fluid is overheated?

 

Diff and trans use two different fluids, so no combing the coolers.

On the diff cooler, need the pump, so would have to mod the pinion gear to work with the Z06 rear cover with pump, the rear cooler and the cooler lines.

 

The car is a non-z51 base 2008 with manual transmission.

I was under the impression that the z51 cars used the transmission fluid in someway to help cool the differential (maybe I was mistaken).

Here is my problem, I am taking the car to the track more often. I had originally planned to change the differential and transmission fluids annually. The transmission shifts great and makes no noises that I can discern. The differential however appears to be making the slightest "binding noises" when making sharp turns at very low speeds. This happened last year and changing the fluid remedied it. The car has approximately 10 events (combo of TNIA style 3 session events, autocross, and a few full day 7 session events) and i have one more scheduled for this year before the cold forces us northerners back indoors.

Is it normal to have to go through 2 changes of differential fluid annually?

What is the easiest/cost effective way to improve longevity of those parts? Is it just change the fluid more often? I don't want to spend the $2k+ on the LG differential/transmission cooler setup.

I am starting to assemble my off season plans and right now they include a larger radiator, power steering cooler, connecting the z06 brake ducts to the hubs for brake cooling, and something (if needed) for the transmission/differential.

Thank you for the advice in advance

 

Assuming your '08 was produced prior to Nov '07, the chances of having the old 2-part differential fluid is pretty high. Your "binding noise" solution/cure may well have been due to changing to the newer fluid which includes the friction modifier. From the sounds of your interest in road track events, changing the fluid annually might not be a bad thing to put on your maintenance list.

The Dewitts radiator for the Z51 option IIRC includes an engine oil cooler and transmission cooler ports. If you're having cooling issues (including engine coolant), you might want to address them individually, rather than combined in one product.

The factory differential cooler is a stand-alone unit that you can add to your current dif and will require a bit more fluid.

While the A6 trans cooler is in the radiator, it's primary purpose for being there is to quickly heat and then maintain the trans temps. You need to attain a minimum 150 F to ensure proper WOT shifting and preferably a 180 F maximum for longevity. The downside to the in-radiator cooler, is the high temps have no limitations. You don't have good control on trans temps with stand-alone coolers either, because the in-line t-stats depend on full flow fluid systems and the A6 is a partial flow style. The best you can do, is to use two coolers with a valve plumbed for switching between one or both depending on fluid temperature.

An easy way to control oil temps is with a stand-alone oil cooler and t-stat. IIRC a t-stat that replaces the bypass on non-Z51 blocks, is available as the easy solution. Try improvedracing.com.

The advantage of stand-alone coolers, is that not only you can size them to fit your needs, you then have the ability to size your radiator without concerns for the need to do double or triple duty cooling.

 

i have already added a z06 oil cooler /w the Improved racing Oil thermostat. Last year in the one event that I did oil temps got over 300 before I would run a cool down lap, now I can run all session and the oil temps get to a highest temp of 284. Oil pressure stays around 40PSI under load and at idle dips down to around 20 when the oil is full hot and comes back up when it cools off. I ran 5w30 this year and will switch to 15w50 next year. Water temperatures are starting to creep up but have yet to go north of 230 as I get faster I expect that coolant temps will exceed that and I plan to proactively address it. I also noticed that I boiled over a bit of power steering fluid on a session last time out so a PS cooler and synthetic PS fluid is on the list for this winter as well.

The thing I am worried about is the transmission and differential. My original plan was to swap those fluids annually as a matter of course but now I am wondering if I need to do it more frequently and/or install coolers to ensure the continued safety to those systems. The differential cooler seems like a complicated part to install, it requires not only a new end plate but some modification of the gears inside to drive the pump in the end-cap. I am not willing/able to do that.

 

While I'm not familiar with the stresses of road racing, the physics and temperature limitation concerns are pretty straight forward. I use my '08 base w/A6 and 2.56 gear for 1/4 mi drags, daily driving, and 2500+ mile road trips. Living in the Phoenix area, heat is always a concern, especially with a high (3600/4000) stall converter. You start to kill transmissions when you exceed 180 F and they go away rather quickly when constantly above 210. I've seen 240 momentarily in heavy traffic, even though I have a relatively good size stand-alone cooler. I'm only under extreme load for 10-12 seconds at a time while racing vs you for 15 minutes. Back when the car was new and bone stock, the trans temps in downtown stop'ngo traffic could reach 225. It's why I suggest you go with a two cooler system, even if one is going through the radiator.

 

You don't have an internal pump in your transmission so you'll need external pumps for both trans and diff

 

that is what I was afraid of. So the next question is this, for 20 minute HPDE sessions is that a requirement? In reading some old threads from the C5Z some people said at an intermediate pace it isn't needed. The transmission doesn't typically get shifted all that often (most courses I run in 3rd gear and have one shift into 4th and one back to 3rd every lap).

Can I get away with just using a higher quality gear oil like Redline? I tried the Redline last year but purchased the wrong fluid (the NS fluid) and then removed it and put the AC Delco in.

Thanks

 

I think you'll be fine at the intermediate level. I track a z51 and just recently added a diff cooler after 5 years. The stock trans cooler uses the radiator which is over 210* on track, so its not doing too much. I use the redline high temp fluids. As you progress, you'll have to decide whether you want to dump tons of time and money into your car or get into something more track ready

 

PM to be sent

 

Yes, the A6 does have an internal pump. If you doubt that, try disconnecting the line at the radiator and start the engine.
The problem is that the pump doesn't create a positive flow, since there is an internal bypass. If you remember partial flow oil filters from the 50's and 60's, it's the same concept.

 

HOXXOH, sorry for the confusion, the car is a Manual.

The transmission/differential cooling is to avoid premature failure of the differential/transmission from overheating as a result of track use. I am going to just make it a point to replace the fluids every 10 hours of track time (or sooner if symptoms appear) which works out to be every 6-8 events. I did 7 events this year with one more scheduled. The 7 events totaled approximately 10 hours and 40 minutes of time on the track.

 

Oops Sorry about that. I was thinking about multiple posts and just lost track of which ones.