Standard trans lower towing capacity than automatic???

[acensor]

I has some Aussi visitors here recently who are now off on a one year RV USA adventure. I helped them purchase a cars -- something I tend to be good at -- but demured on helping them find a trailer. They're off on the road now with a Ford F-150 and a 18 foot trailer, and seem to be doing OK.

But we had a puzzling thing happen that I wanted to bounce off you experienced RVers:
I had found them a real creampuff1997 Ford Explorer V6-4liter standard transmission in EXCELLENT condition and with one owner and complete service history indicating far-better-than-average-maintainance. I looked up the towing capacity for the V6 and it was quite adaquate (over 5000 pounds) for what they were then contemplating pulling. This made sense to me because the displacement of the V6 at 4 liters was only 20% less than the V8 at 5 liters. So they purchased it, drove it for a week and were delighted with it.

When they went out trailer shopping the RV dealers told them that the V6 standard transmission was only rated for pulling 3500 pounds (marginal or even below for what they wanted to pull) -- that the approx 5000 pound figure only applied to the V6 automatic. So sadly, they had to trade in the Explorer.

Now I find it hard to believe that the standard tranny would have a lower towing capacity than the automatic because one of the main problems/weak points of towing with marginal towing capacity is overheating of the automatic transmission fluid -- which can't happen on a 5-speed. I have been unable to find hard information confirming or denying the reality of the V6-standard having a lower towing capacity than the V6-automatic. And my imagination/speculation is that, if in fact that's a real Ford Motor Company offical spec, that what's going on is not REALLY that the V6 5 speed can't haul the bigger load, but that Ford'se covering their ass by assuming that with the standard tranny some idiot will try to pull a 4000 pound trailer up a long freeway slope in 5th gear (something that can't happen with the automatic, which will downshift itself) and burn out the engine and sue Ford. That's pure speculation on my part.

Can anyone confirm that the standard tranny does, or doesn't, really have a lower towing capacity? And if so, why?

Just curious at this point, for future reference.

Alex
P.S., I'm not a regular lurker here, since I have no RV currently, so if you reply and are able to send me a copy by email to [email protected] I'd love that.

 

[Karl]

Alex,
If you had two identical vehicles as far as engine horsepower, weight, wheel size, etc., the one with the automatic tranny would indeed have a higher towing capacity. The reason is quite simple. The automatic tranny is coupled to a torque converter which does, among other things, multiply the torque from the engine up to 2-3 times, giving more power to the real wheels. The heat generated by the converter is routed thru the tranny fluid and dissipated by the radiator and an optional (but usually present) auxilliary tranny cooler. The standard tranny has no such torque converter, so the friction of the clutch trying to get the vehicle moving generates a lot of heat that has nowhere to go, so it would burn out in short order. Also, don't assume that the standard tranny doesn't generate heat and can't overheat. When the engine spins the input shaft and the power goes thru various gear combinations and bearings it must overcome their friction and inertia, and also overcome the viscosity of the lubricants; therefore heat is generated - quite a bit of it.     

 

[Gary RV_Wizard]

Ford may well have used a standard tranny of lower capacity that they had in their parts bin.  It was likely designed to a lesser spec than the auto.

But it is also true that an automatic has an advantage in the torque converter. As long as it can successfully shed the heat from converter slippage, that slippage allows the drive train to successfully move  large loads that would cause a standard transmission clutch to quickly burn out.

 

[Karl]

Good point, Gary.
Also, the rear end ratio is usually different with a stick.

 

[Carl L]

Your whole experience emphacizes one thing.  A person cannot buy a tow vehicle without checking out the manufacturers tow rating for the exact combination of engine, transmission, and rear end of any given vehicle.  One can find those listings with Trailer Life on their web site for current and recent model years.  One can also find it in the operators manual of the given vehicle under towing -- at least one should.  Really good dealers may even have the listing for their current model.

The auto vs. manual tranny issue is much as kkolbus has it.  That said, I believe the issue in big desiels is different and should be checked out as I recommend here for a specific vehicle.

If I were in the market for a trailer/tow vehicle combo today, I would proceed as follows:

• 
  1.  Decide on the general features of the tow vehicle:  4WD?  Pickup, van, or SUV?
  2.  Decide on the general floor layout of the trailer and get an idea of the weight ranges in lightweights.
  3.  Match the general features of the tow vehicle with a tow rating appropriate to the trailers available.  Use a required tow rating equal to the trailer gross weight rating PLUS a headroom of 10% -- make thatr 20% if you plan to tow in the Mountain West of the US or Canada.
  4.  Buy the tow vehicle that is indicated by 1 and 3.
  5.  Buy the trailer to fit it.

This means a bit of shopping.  With the tow vehicle, I used a broker with list of my specifications.  He eventually located my desired crate with a dealer 120 miles away.    With the trailer, I simply went to a RV center of some ten dealerships and started wheeling around in the tow vehicle.

 

[wilfreddrabble]

Regarding the manual transmission Explorer with the 4l V6.

There is a specfic issue regarding towing with this vehicle which I have run into myself. I used to tow with a 1999 Mazda B4000 pickup which has the identical driveline to that of the Explorer.

The 5 speed manual transmission on this Explorer (as on my Mazda), which incidentally is one of the only Japanese parts on these vehicles, has a much too high first gear. Even with a 4.10 rear axle ratio, first gear starts on hills are problematic.

This bad situation could have been totally avoided by Ford. When this same transmission is used with the 3.0l Ford V6 (I don't think this engine was available on the Explorer but it was on the Mazda and Ranger pickups), the lfirst gear ratio was 3.7, a big improvement.

The first gear on any manual transmission in a truck should be very low - all wound out at about 10 mph. Trucks should be made in such a way as to haul & tow the heaviest possible loads and geared accordingly, IMHO.

If I were to buy another Ranger/B4000 4 liter V6/5 speed manual, I would have the transmission rebuilt with the lower ratio first gear cluster.

John Alldredge

 

[John From Detroit]

They yammer about how much they can tow.. but don't put in the right trans.. How auto-manufacturer can you get ?