I tried went to buy some GM rear diff oil and additive from a local dealer *cough*MichaelSteadinWalnutCreek,Ca*cough* a few weeks ago - $49/qt for the oil and $30 for the additive! If I didn't know any better I'd say they are trying to get us all to void our warranty
I ended up going across the street to Napa and getting the same spec in Valvoline synthetic for $10/qt.
That's crazy. I changed the trans fluid and diff oil two years ago in my Firebird. For the diff I got Valvoline Durablend 80W90 from Advance Auto for about $11. I bought the additive from the dealer, but I think it was only about $12. I guess it's gone up since then.
I don't know why dealers jack up the prices to such stupid levels, you'd think they'd figure out they could sell a lot more parts if their prices were competetive. Then again maybe they don't want to sell a lot of parts. For example... the driver's side window motor finally died on my firebird last year, dealer price was around $160. Bought the same identical brand new OEM part at my favorite 'old-style' parts store for $68. I can understand they need to make a profit and they mark up their parts, but that's over 200%.
Good news: Took my GTO to the dealer this morning for its 4000-mile oil change. They sent me a coupon a while back, so I got the whole service for $15.95 and that's with Mobile1 oil. Can't beat that with a stick. Also asked the tech to check for any leaks anywhere while he had the car on the lift, he said it's dry as a bone.
More good news: Just finished changing the rear differential fluid to RP Maxgear 75-140. Easy job, 30 minutes tops. Only spilled a few drops.
Bad news: It started raining just as I finished up, and I don't want to get my freshly washed and waxed car out in the rain, so I'll probably have to wait till tomorrow to see if I can tell any difference after the rear end fluid change.
I'm really impressed with the Royal Purple fluids. I added the Maxgear 75-140 to the rear end, no friction modifier necessary--smooth and quiet. Not that I was having any rear diff noises before, just wanted a better fluid with better protection. Love the Synchromax in the trans too, shifts are smooth and slick and the trans does seem a little quieter.
I also added a K&N drop-in air filter. Seems like it feels a little more responsive. Just drove the GTO to the Florida coast last night, 356 miles in a little over 5 hours. Averaged 23.5 mpg running 80-90 mph with the car packed pretty well (that's better mpg than my wife's minivan with an anemic v-6). And I still have 400 hp on tap to get around the slower drivers. I swear there were several times I'd look down and find myself doing 100mph+ and never had a clue... it's so smooth. I love this car!
I did the RP changout too when I had my GMM Ripshifter put in. I've noticed a little better mileage but the tranmission is pretty noisy. I'm guessing that's because we left the black rubber seal off (made 4 hard to get into). I'm thinking of putting it back on and cutting out a notch or something. The RP did eliminate the rear end noise I'd had.
I'm still running the stock shifter, I've heard the Ripshifter can be noisy. I'll probably go with the Lou's short stick and leave the rest of the shifter alone.
My mpg went up too, I usually average around 22.5 mpg per tank with about 80-85% interstate travel and the rest city & town driving with an empty car. I think I can get an average of about 24mpg per tank now, considering I got 23.5 and had the car fairly loaded (as far as you can load a GTO with its tiny trunk).
My only real complaint with driving the car over a long distance is the tilt wheel, I really wish it came down about another inch. My arms got kind of tired. The seats are pure pleasure to sit in. I only stopped one time for a quick restroom break and to grab a cold soft drink.
Have the same complaint about the stupid wheel not lowering enough, so had to learn to grab the wheel at the 3 and 9 o'clock positions to alleviate fatigue on my arms from the 12 o'clock position I've used all my driving life.
As far as the fluid changes, I changed all 3 at 540 miles. Also replaced both tranny and diff with RP (75/140), but my diff didn't like the RP stuff. After reading all threads on the subject over the LS2 site (many), the consensus was the best diff fluid for our cars is Torco RGO 85/140 with 2-oz of type-F (not G) modifier. This was recommended by a very large differential shop which did extensive testing with all other oils.
I decided to replace the RP with the Torco, even though the Torco is NOT a synthetic fluid, but after not finding ONE bad comment about Torco on our diffs, and many about RP (especially the 75/140 weight), I opted for the change. Tranny feels great, and RP is the overwhelming fluid of choice, so no problems there. At the very least, 85/140 should be used instead of 75, even though that's what it's called for on the manual. Many other cars use the same differential as our cars, so it's not unique in any way.
My differential started whining noticeably more with the RP (but no chatter, so no more FM was needed), but I was driving without the back seats for a while; nothing could be heard with the seats in place. However, I didn't like that, and that's why I changed it to Torco. Maybe RP 85/140 would have made the same difference as Torco; who knows. But decided to put what the experts on that diff recommended. Hope this helps.
JC
Few comments. Checked my car today, and first thing it was obvious was no way in hell a pipe can be UNDER the steering rack, so no power steering fluid would ever hit a pipe. Second, both cats are not close enough to the rack to cause any problems IMO, so it's almost obvious those guys had aftermarket headers and (high flow) cats installed. Finally, checked those 2 big bolts/nuts, and no leaks in my car.
If you don't have headers, disregard my comment about having problems with the steering rack. Hope everybody had a great easter weekend gang. Later.
JC
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