Manual vs. Automatic GVWR

[logboy33]

For the life of me, I cannot figure out why there is such a big difference. Example: my 2000 Ranger 4.0 FWD, 4.10:1 rear end, manual tranny has a GVWR of 7000 lbs, but (according to my owners manual) if I would have gotten an automatic, with all other spec the same, the GVWR is 9500 lbs. Can anyone shed some light on the disparity of the numbers? I'm just a dumb electrician and it has me baffled.

Thanks in advance! -Roger

To clarify, I know how GVWR is determined, I'm just confused why the rating would be so much greater simply because the vehicle is equipped with an automatic transmission. In this case, towing limit with a stick shift is 3160 lbs, towing with an automatic is 7000 lbs. Why, oh why?

Update: My thanks to all who contributed answers. I think the clutch may well be the limiting factor, especially if it is abused. I just bought a new trailer which exceeds the mfr's towing weight limit, but I'm not going to worry about it. I know how to treat a clutch, and I do not anticipate any problems. If there are any probs, I'll take the hit. Thanks again - you all rock!

 

[Thed]

Gross Vehicle Weight Rating is what the manufacturer rates the vehicle's total weight limit as. Say your Ranger weighs 3500 lbs and your GVWR is 9500. That means that you can have your Ranger and 6000 pounds worth of crap on it (I dont recommend that) or towing it, humans included.

Basically take the GVWR and subtract your Ranger's weight and the result is how much you can tow.

 

[triumphrider-1]

From what I understand, the reason the manual trans version is so much less is because of the clutch and lack of a cooler.

 

[kryptonitecb]

Manual transmissions typically don't have options or a need for a cooler. The fluid is really just a lubricant in a manual were as an automatic uses the fluid to move the vehicle.

Sent from the road while ignoring traffic

 

[superds]

I've always believed it was a warranty issue. To prevent warranty claims (and pissed off customers) of burnt up clutches (because people use them improperly) they rated the manual transmission versions of the same Ranger lower than an automatic transmission.

 

[alwaysFlOoReD]

I've always believed it was a warranty issue. To prevent warranty claims (and pissed off customers) of burnt up clutches (because people use them improperly) they rated the manual transmission versions of the same Ranger lower than an automatic transmission.

imo this

 

[logboy33]

That really makes a lot of sense. . .

I've always believed it was a warranty issue. To prevent warranty claims (and pissed off customers) of burnt up clutches (because people use them improperly) they rated the manual transmission versions of the same Ranger lower than an automatic transmission.

I have ALWAYS had manual transmissions (except my first car, '54 Chevy w/power glide) and have NEVER worn out a clutch. I think you are right, and that most of America doesn't treat clutches with the respect they deserve.

 

[Gacknar]

The difference is the ability of the torque converter to multiply torque.

http://en.wikipedia.org/wiki/Torque_converter#Efficiency_and_torque_multiplication

 

[Mac]

This subject comes up every so often. Everyone has their own option (I'm for auto's for towing). What really fails in the manual trans? Is it the small clutch dia or what?
Dave

 

[85_Ranger4x4]

This subject comes up every so often. Everyone has their own option (I'm for auto's for towing). What really fails in the manual trans? Is it the small clutch dia or what?
Dave

The clutch is the weak link for starting a load... and I bet Ford got queezy about people that don't know how to operate too.

 

[lil_Blue_Ford]

The clutch is the weak link for starting a load... and I bet Ford got queezy about people that don't know how to operate too.

I say it's certainly possible that the reason has a good bit to do with the clutch. I picked up an F-150 a couple years back, 69k miles, guy said it sat most of the time because he drove his car instead. Within about 1,500 miles of me having the truck, I discovered the clutch was toasted. I'm pretty sure the guy didn't tow with it since it didn't have a hitch.

My Ranger has around 90K with the original clutch. The F-350 dump I drove for work for years had over 100k on the clutch when my boss sold it. His other F-350 has 116k on the original clutch. All three of those saw towing/hauling duty on a regular basis, but both myself and my boss knew how to drive a manual trans.

My F-150 has taken over towing/hauling duties from my Ranger and I rolled 100k not too long ago (around 30k on the new clutch).

I like driving manuals, especially for towing (although I hear some of the new autos are supposed to be pretty good), but a lot of people don't seem to have a clue and really kinda have no business using a manual much less towing with one. Being able to get a load moving is only part of the issue with towing. Being able to control it and stop is the rest (and stopping may arguably be the most important).

 

[adsm08]

When you come at it from the position of towing a properly cooled automatic is much stronger than a manual trans for a few reasons.

1) Auto trans has many clutches. They are smaller in diameter than the one on a manual, but there are 6 or 7 of them per pack spreading the load out across the different discs. Incidentally, that clutch material melting off the plates is what turns the fluid that nice shade of black when you cook the trans.

2) Constant mesh gearing. The manual uses sliding engagement gears that have partial contact. The amount of space that comprises the smallest (weakest) part of the link is actually pretty scary, and the fact that the gears move in and out of contact as you shift weakens the link. Automatics use planetary gear sets, which have a larger contact surface, and are in constant contact with each other, no sliding in and out (during normal operation anyway). So until you crack a planet gear the planetary set is much stronger.

3) Torque converter: As stated, the converter ramps up the power that can be put to the wheels at low speed. When the engine-driven side of the converter fan is spinning much faster than the other side the fluid gets run through a stator in the converter and you get a torque multiplication effect. Now this gets reversed at high speed once the vehicle is moving, but that is why we have lock-up converters now.

The converter also provides a fluid coupling that evenly and smoothly applies the engine power to the trans every time, no feathering, no jerking, no getting it rolling, drop the clutch, and bring it up again. That is a lot less shock and stress on the trans.

 

[kryptonitecb]

^^^^^
Thanks for the info, lot of stuff I had no clue about in there.

Sent from the road while ignoring traffic

 

[adsm08]

One other little thing about autos, and I find this to be the most interesting thing about them, they are a rip off. Really.

You pay a lot more for a car with an automatic transmission, but the auto costs more to maintain, more to fix, and less to produce. Most parts in an auto are cast, a fairly cheap process. The internals of a manual are machined, which is comparatively expensive.

 

[85_Ranger4x4]

One other little thing about autos, and I find this to be the most interesting thing about them, they are a rip off. Really.

You pay a lot more for a car with an automatic transmission, but the auto costs more to maintain, more to fix, and less to produce. Most parts in an auto are cast, a fairly cheap process. The internals of a manual are machined, which is comparatively expensive.

The autos are more in demand than a manual and they have a lot more electrics nowadays.