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by Vince Spinelli - covers Chrysler / GM New Venture Gear 3500 / 4500 / 5600 Transmissions, 1995 through 2007 (+?)
The question of “What lubricant do I use to drain/fill (service) the standard shift transmission in my Dodge, Jeep, or GM truck?” has plagued many a mechanic for some time now. Previously, we'd all been under the impression that 75-90 GL-4 was the way to go. Not true, at least not any more.
The Dodge 2003 DR Ram Truck 1500-2500-3500 Shop Manual, Volume 1, states:
So, the NV4500 is a given; use any high quality 75W85 GL-4 Synthetic Gear Oil. Items such as Mobil 1 Synthetic, Castrol Syntorq, or Valvoline Synpower will all do the job nicely. But be warned, the spec is for GL-4 lubricant, NOT the commonly available GL-5 that we've all been using in our front and rear axles these past few years.
API (American Petroleum Institute Classification) GL-4 (Gear Lubricant-4) contains about half the additives of GL-5. Higher concentration of Extreme Pressure additives in GL-5 gear oils may cause the softer metals, such as copper, brass and bronze – which make up the shift synchronizers of a manual transmission - to suffer premature wear / failure. So, stick with the specified GL-4 classification, in any of your favorite synthetic brands.
The NV3500 and 5600, however, leave us all wondering what magic potion this 'Mopar Manual Trans Lube' (or in the case of our GM folk, 'GM Manual Trans Lube') has within its chemical makeup. Well, you might be surprised to know that the recipe is very close to the average 5w30 motor oil.
DISCLAIMER: Use of lubricants that do not SPECIFICALLY meet that of the manufacturer's specified lubricant may void the vehicle's warranty. Use of non-OEM recommended lubricants (or lubricants which are not guaranteed to meet or exceed OEM lubricants for the specified use) is at the risk and liability of the vehicle's owner, not the author or publisher of this article. Use of the Mobil 1 product for this purpose constitutes acceptance of this disclaimer. See the longer disclaimer at the end of this page.
Please note that 5w30 motor oil is not a far cry from 75w85 gear oil. In fact, 10w40 is about the same consistency (under thermal stress) as 75w90 gear oil. The numbers may seem far off, but they are much closer than many may realize.
As it turns out, Castrol was brought in by New Venture Gear (a joint transmission-design firm once owned by Chrysler and GM cooperatively) to find or develop a suitable lubricant for the new transmissions. While 75w85 GL-4 sufficed for the 4500, a gearbox aimed primarily at medium duty work trucks, the 3500 and 5600 (which would go into service as mainly daily drivers, and thus designed for a blend of quality driving and medium duty work) required something more refined.
According to sources which aren't named, the Castrol (owned by British Petroleum, aka “BP”) remedy was a 5w30-”ish” full synthetic, meeting the API specification for energy conserving gasoline engines, and tested to be safe for yellow metals, the copper, brass, and bronze that we spoke of earlier. A standard 'dinosaur' crude-oil engine oil would likely meet this demand, however it would require too frequent a change interval (to prevent sludging and oil breakdown) for transmissions.
FIVE YEAR FOLLOW-UP
Around five years after writing this article, I've tallied around 40,000 miles on the truck. Performance was as expected; which is to say that it wasn't any different. Upon draining the lubricant, it appeared clean and of sound body (which is a vague way of saying that it did not feel broken down between one's fingers). There were a small number of metal shavings on the drain plug magnet - nothing alarming at all.
It sounds like a success doesn't it?
About two months (500 miles) ago, it would occasionally 'chirp' going into first or second gear. Now, on any given day, at any given time, it'll chirp / grind a tad bit going into any gear - a telltale sign of a synchronizer issue.
There is insufficient detergent agent in the alternative Mobil 1 product to adequately serve in this application. While it does the job of lubrication and longevity just fine (as noted, it's still clean and integrated at 40k miles with a suggested change interval of 50k), deposits and the byproducts of use (wear material) are not being sufficiently dissolved.
On the flip side, in the years since my initial article, local chain auto-parts stores have begun carrying commodity rate alternatives. Nearly every store in my corner of the country stocks at least one of the two following fluids, which are certified direct replacements for the OEM lubricants...
-- Pennzoil Synchromesh ($8.75 / quart - 2012)-- Royal Purple Synchromax ($8.50 / quart - 2012)
As others have noted, Amsoil Synthetic Synchromesh is also available at similar pricing, although you may have to order it.
So - I filled up on the Pennzoil, and within a few hours of driving, the transmission started to quiet down - not a lot, but enough that it was noticeable. Hopefully, it'll work itself out over the next few weeks.
Moral of the story... if you need to top off, or had a leak; or if you're just in a jam - the Mobil 1 product will work great in a pinch, and it will sufficiently lubricate the transmission. However, long term use may lead to premature synchro failure (hard shifting / grinding).
Supposedly this is a 'lifetime' lubricant... but after draining the casing in my 2003 Ram, I found enough 'gunk' and metal shavings to make me cry. Nothing in the world is a lifetime lubricant. If treated with kid gloves, 100,000 miles is a reasonable change interval. However, when other people are driving your vehicle, or if you learned how to drive stick on your vehicle, or – whatever – you're going to want to cut that down to a 50,000 mile change interval or so. Only you can be the judge; consider your driving habits and the work level you use your vehicle at (industrial, moderate towing, light towing, simply daily commuting, other).
That being said, the Castrol formulated mystery lubricant is available from your local GM or Chrysler dealer for anywhere between $15 and $30 per quart (prices as of July, 2007). Considering you'll only need 3 to 4 quarts (the 3500 only calls for 2 quarts, but by the time you pump it in and spill a little, you'll end up using a little over 2, so buy 3... the 5600 requires more... remember, do not overfill, simply to the bottom of the fill-plug orifice), it's likely not a big problem to plunk down $45 to $120 at your local dealership. But, if you can get the same quality of protection and performance, for less than half that price, and not have to wait for your dealer to be in stock of the item, then why shouldn't you walk right down to your local auto parts store and fulfill your needs?
After a bit of research and phone calls to the help lines of Valvoline, Texaco-Havoline, Pennzoil, Quaker State, Castrol (who were shockingly unhelpful), and Exxon-Mobil, I've found what appears to be the only off-the-shelf replacement lubricant that meets the standards of the OEM lubricant.
That is – Mobil 1 Synthetic Extreme Performance 15,000 Mile 5w30 Motor Oil.
This lubricant meets the viscosity and thermal requirements of the OEM lubricant, is designed for severe duty and to prevent shearing of the lubricant under high temperature and stress (as modern manual transmissions are subjected to the heat of modern emissions required catalytic converters, which sit about 6 inches away in most cases), and is promised (according to Exxon-Mobil help line as of July 2, 2007 at 12:30 pm EST) to be safe for bronze, brass, copper, and most other 'yellow metals'. Castrol, Valvoline, and the rest stated that their products were not tested against brass, bronze, or copper, which surprised me considering that many camshaft bearings are made of bronze in newer vehicles such as the recent LS-1 Corvette. This may be a different grade of bronze than others speak of when the term 'yellow metals' is used. I, however, doubt that.
The moral of the story is that many synthetic 5w30 oils may do the job quite nicely, however, at this time none of their manufacturers are willing to state on record that the product will perform in the given environment. As such, only Mobil 1 Synthetic Extreme Perf 15k Mile 5w30 fits our needs.
The change interval should be the same as the OEM Castrol developed product, and there should be no adverse affect on shifting or synchronizer function/lifespan.
The cost of the Mobil product is roughly $6.50 to $7.00 per quart (as of July 2007, from partsamerica.com // Advance Auto, Checker, etc.).
Amsoil does make a Synchromesh 5w30 that is guaranteed (by Amsoil) to be direct replacement product for the Mopar / GM OEM lubricant, but Amsoil's product is not regularly stocked (as of July 2007) at any national chain auto parts stores that I am aware of. The Amsoil product is approximately $8.50 per quart, a very fair price for a fluid that is guaranteed to be direct replacement. Nonetheless, for an 'off the shelf' lubricant, Mobil 1 Synthetic Extreme Performance 15,000 mile 5w30 is where it's at.
I'll write a very brief follow up to this article [see sidebar for five year update] to let everyone know how my own personal trial of the Mobil 1 lubricant has played out.
— Vince Spinelli, July 20, 2007
Updates: C. Glosson wrote, “The 5600 can be serviced with a Pennzoil Syncromesh oil — it has the Chrysler endorsement on the bottle.” We checked and it was $9 per bottle at amazon.com.
Barry Crudup, an active and polite Allpar forum member, pointed out that Amsoil also makes a Chrysler endorsed replacement for the Mopar oil, at (as of August 2007) $8.60 per quart, retail, plus shipping.
DISCLAIMER: Should your vehicle be under warranty, use of lubricants that do not SPECIFICALLY meet that of the manufacturer's specified lubricant may void the vehicle's warranty. The above recommended Mobil 1 product does NOT specifically state that it is a direct replacement for the OEM Chrysler or GM lubricant. It is simply the author's educated opinion based upon research and contact with lubricant manufacturers (as well as implementation in his own vehicle) that said product will perform as necessary. Use of non-OEM recommended lubricants (or lubricants which are not guaranteed to meet or exceed OEM lubricants for the specified use) is at the risk and liability of the vehicle's owner, not the author or publisher of this article. Use of the Mobil 1 product for this purpose constitutes acceptance of this disclaimer.
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