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Nonno · 02-02-2007, 06:31 AM

Certain vehicles in the guide show a MPH limit. For example the Nissan Frontier shows 60mph. What happens if I average about 67mph?

Nonno · 02-02-2007, 06:31 AM

Certain vehicles in the guide show a MPH limit. For example the Nissan Frontier shows 60mph. What happens if I average about 67mph?

hondo122 · 02-02-2007, 01:55 PM

The wheels fall off!

hondo122 · 02-02-2007, 01:56 PM

Just kidding, I hope some one does, would be interesting to know.

Nonno · 02-02-2007, 03:14 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> The wheels fall off!
</div></BLOCKQUOTE>

At least I wouldn't have to worry about it passing me.

I stopped by a Nissan dealer today and took a look at an operators manual. No mention of the 65mph limit, just the need to idle engine every 500 miles.

alvinc · 02-05-2007, 09:36 AM

I have wondered this myself.....why do some makers specify speed limits?

I can think of three possible reasons, others might think of some more:

1) The maker did some statistical number crunching and deteremined that above this number the wear and tear will the warranty claims, so they they limit the speed to protect themselves. Don't know how they could prove that it was towed over the suggested limit?

2) The maker did some tests and found that as the speed increased it is more likely that the churn in the transfer case or transmission will cause damage. In most cases the lubrication pump is not running and they are depending on oil hanging around for lubrication. The oil might foam or overheat as the speed increases.

3) The maker has determined that churn in the transfer case or transmission will cause upstream elements to turn (this is why Jeep has you put the transfer case in neutral and the transmission in gear/park) thereby causing damage.

Others?

bobwallace · 02-18-2007, 07:10 AM

I have a 99 Frontier 2 wheel drive that has at least 50,000 towed miles on it. It has been behind 4 different MH's. Speed ranging from 55-75. No problem so far. It has a manuel tranny.
Cheers Bob

paz · 02-18-2007, 05:11 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by alvinc:
I have wondered this myself.....why do some makers specify speed limits?

I can think of three possible reasons, others might think of some more:

1) The maker did some statistical number crunching and deteremined that above this number the wear and tear will the warranty claims, so they they limit the speed to protect themselves. Don't know how they could prove that it was towed over the suggested limit?

2) The maker did some tests and found that as the speed increased it is more likely that the churn in the transfer case or transmission will cause damage. In most cases the lubrication pump is not running and they are depending on oil hanging around for lubrication. The oil might foam or overheat as the speed increases.

3) The maker has determined that churn in the transfer case or transmission will cause upstream elements to turn (this is why Jeep has you put the transfer case in neutral and the transmission in gear/park) thereby causing damage.

Others? </div></BLOCKQUOTE>
4) The vehicle will not track properly above the specified speed. It may bounce on uneven pavement or wander and fishtail.

5) The manufacturer wants to cover himself.

NeilV · 02-19-2007, 12:57 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by paz:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by alvinc:
I have wondered this myself.....why do some makers specify speed limits?

I can think of three possible reasons, others might think of some more:

1) The maker did some statistical number crunching and deteremined that above this number the wear and tear will the warranty claims, so they they limit the speed to protect themselves. Don't know how they could prove that it was towed over the suggested limit?

2) The maker did some tests and found that as the speed increased it is more likely that the churn in the transfer case or transmission will cause damage. In most cases the lubrication pump is not running and they are depending on oil hanging around for lubrication. The oil might foam or overheat as the speed increases.

3) The maker has determined that churn in the transfer case or transmission will cause upstream elements to turn (this is why Jeep has you put the transfer case in neutral and the transmission in gear/park) thereby causing damage.

Others? </div></BLOCKQUOTE>
4) The vehicle will not track properly above the specified speed. It may bounce on uneven pavement or wander and fishtail.

5) The manufacturer wants to cover himself. </div></BLOCKQUOTE>

6) The front cross member won't handle the stress above that speed and start to fatigue.

7) Limited slip or traction control devices could engage or possibly overheat causing loss of control a fire or both.

8) Common sense dictated that it is just not that good an idea to go over a certain speed so they set a max based or what they felt was reasonable.

Of course it really does not matter as the limit is the lower value of the two comparing the manufacturers max allowable speed to the local/state laws governing the max allowable speed when towing. I believe that the State limits will be lower and the winner.

Gary RVRoamer · 02-19-2007, 06:00 AM

All the above reasons apply, but primarily it is CYA and warranty concerns on transmission overheating.

In just about every design, an automatic transmission turns some internally, even in a 4x4 with transfer case in neutral. That because the couplings are generally hydraulic, so it is never totally disconnected.

Higher speed generates more internal motion and more heat, especially when the tranny is not circulating fluid for cooling and lubrication. Ergo, higher speeds and more miles increase the likelihood of wear and stress. The engineers pick a number where they feel confident that the combination of speed and miles driven will not cause problems beyond their warranty cost projections.

What happens if you exceed the speed? You get a bit more wear and tear. Likewise if the recommendation is to stop every x miles and run the engine a bit to circulate fluids. Failure to do either may or may not result in obvious problems during the time you own the vehicle, but it has definitely increased wear on the transmission. You can monitor this to some extent by frequently checking the transmission fluid for signs of overheating. If it remains a nice bright red and has no "burnt toast" aroma, you are likely OK. If the fluid gets dark or dirty looking or has any burned smell, you have already overheated your transmission and caused some damage. Maybe a little or maybe a lot... In any case, immediately change the tranny fluid if that happens.

We have owned two Chevy Trackers that had a 55 mph tow speed limit and a 200 mile range between running the engine to re-lube. I always ignored the tow speed limit and religiously observed the 200 mile range (we usually stopped for a break by then anyway) and never had a problem in 55,000 miles of towing.