5W-40 in summer and other questions?

[FightinTXag]

I've got 1500 miles and after a trip home to Dallas this weekend I'll probably be a little over 2000. I'm going to do my first oil & filter change, change the Alli filter, and rear diff fluid.

I think I remember looking at the diesel supplement manual and seeing 5W-40 is good for extremely low temperatures (that I'll never see in Texas), but the upper limits of the 5W-40 vs 15W-40 weren't shown. Is there any concern with 5W-40, towing in 100+ degree heat? I'd really like to run Delvac 1. Being a full-synthetic, it should handle the heat better than dino 5W-40, right? Would I be better off finding a full synthetic 15W-40? Does anybody aside from Amsoil make such an animal?

Where can I find the Alli filter? At 25,000 I'm planning to change the Alli fluid and filter again. Where can I buy Transynd? Is that the best tranny fluid available?

I don't want to go plunk down the bucks for the grape juice. I'd bet my dealer doesn't even have it in stock. For heavy towing apps I've heard recomendations for 75W-140. Is there any drawback to using 75W-140 when running empty? Any recomendations for a synthetic diff fluid and where I could find it?

[Kennedy]

I always recommend quick, EARLY oil changes with petro (inexpensive compared to synthetic) to flush out the break in metals and dirt from assembly. Once a couple/few dumps have been made, then I switch to synthetic.

Now if it weren't for the dirt/contamination factor, I'd go synthetic from day 1!

Don't let the 5w scare you with a good and true synthetic. If you cannot get past the 5w, run the Amsoil 15w40, and dont look back.

Transynd is the Allison recommended fluid for severe duty, and what I am personally running. It has worked very well for them BUT, if you look at Castrol, I beleive I was told that there is really no refinery? in the US? Furthermore, Mobil has been hot on their tail in court fighting their "fuzzy math" approach to the use of "synthetic" terminology. Makes you wonder...

[ 08-02-2002: Message edited by: kennedy ]</p>

[george morrison]

Confirming what John has already shared with you, the Delvac 1 5W-40 is essentially a straight 40W which just happens to pour at 60 below zero. One of the many advantages of a synthetic base stock is that it not only does not thicken at cold temperatures as do mineral based oils, but synthetics do not thin at high temperatures. Thus the film strength, thickness at high temperatures is unequalled. This is one reason why I can tell almost immediately what oil a trucking company is using when I walk in their garage. If I see a skid of turbo-charger cores laying there I know the company is using mineral based diesel oil. If there are no cores, synthetic. Turbo-chargers are one of the overlooked high temperature areas where, in long term, the differences are really discernable.. As we have discussed here before, jet engines use nothing but full synthetic oils. These engines spin at 20,000+ rpm with core temps through the roof, and use a 10W full synthetic which lasts 10,000 to 30,000 hours!
Yes, you are completely safe with a 5W-40 synthetic....

[Texas Rancher]

Like JK said, it is very wise to change the factory break-in oil when you get about 500 miles on the truck. You really dont need to change the oil filter at that 500 mile service interval, but surely change the oil. There is a lot of silicon floating around in there.. I have been around diesel engines for a long time, and have repaired and overhauled everything thing from Caterpillar Bulldozer motors to big ag. tractor engines to semi truck engines, and a lot in between. I will not put ~anything except 15w-40 in my engine(s). I believe the heavier oil will help with the ticking of the D-Max, too!
You can get the little red tranny filter at a Stewart-Stephenson or a Allison repair shop. There are a few semi-truck places around here that service Allison trannys. They have the filter, or can get it fast. For goodness sake, dont go to the dealer to get one!! (mega-$$)
I am not trying to come across as argumentative with the about posters, but I own semi trucks, combines, tractors, and several diesel pickups. The 15w40 oil is a great choice in any climate/condition. That is not necessarily to say that other options/choices are no good--but the 15w40 will never do you wrong.

[BadDog]

Ok, I'm a newbie to the D/A so I'm still confused on allot of this stuff. I'm preparing to do the first fluid changes too, although I've just learned, not nearly as early as I should have (I've got just under 3k on mine). Oh well, live and learn...

Anyway, I've seen posts on here that the Allisons use/need Transynd, but my manual (including the Diesel supplement) list Dexron III for all Autos. Transynd is only listed for manuals. So, when I replace the spin on (very soon), what should I use to top it off? What is in there from the factory?

On the rear diff, I'm also interested in alternatives for the GM rear diff synthetic. Is it worth the money GM wants? Are there equally good (better?) alternatives that cost less?

[IndigoDually]

Dextron III is what comes in the Allison from the factory. If You are still looking for a filter for the trans then go to Allison.com and do a dealer search. If there are not any local dealers, call the closest and see if they will ship you some. They are $7-8 from Allison and an obscene amount from the dealer. If you pre-fill the filter you won't lose more than a cup before it stops draining. It's so easy you will want to do it more often(can't hurt).

I am running Amsoil in the rear and still am using Dex-III. I will probably change to the deep pan soon but still use Dex-III.

John

[gdblake]

Just stopped at an Allison dealer in Gainesville TX--Transynd is about $11/qt in gal containers here--$8.50 bulk, if you bring the jugs. I'm going with Mobil-1 at 4.99/qt, since Allison doesn't warrant the trans, and GM won't honor the 50K change with Transynd.