FedEx Calculating incorrectly, but USPS is not.

[autoparts4america]

I have been looking around the forums and google to try to find a solution to what seems to be a repeating occurrence. FedEx calculates the shipping lower than they are suppose to be. However USPS calculates the shipping how it is suppose to be.

We have set the maximum weight = 50.
the tare for the small/medium packages 0:0
the tare for large packages 0:0

The difference wasn't too great to make a difference until we added Tires to our products, and being heavy as they are, the problem only got worse.

Our version of Zen Cart is 1.3.8a and the version of the FedEx module that we are using is FedEx by Numinix ver. 1.45.

Another grave issue is that when the total weight of the packages exceed 70lbs (FedEx maximum lbs per package and google uses FedEx). Google checkout does not work, it say "Oops! We were unable to process your request."

So FedEx module is miscalculating and google checkout is not working. Any tips on what I can look into to try to solve my problem?

[autoparts4america]

I'm still using 50lbs as maximum weight.
When using a 23lbs tire as reference when when set to two (46lbs).
the website calculates shipping as 43.94$, though its suppose to be 52.99$(its bad, but not too bad).
However when I set the qty to 4 with a total 92lbs the website calculates the shipping to be 53.68$
while its suppose to be 105.98$ (definitely bad).

Based on the FedEx debug, it seem that the website is splitting the number of packages into two
and each are 46lbs. I don't understand why the outcome is like this. We are shipping from 33326
to 95361 in the United States for this reference.

Here is our fedex settings
cURL Proxy
NONE
Debug Mode
False
Weight Units
LBS
Which server to use
production
Drop off type
1
Fedex Domestic fixed surcharge?
0
Fedex Domestic variable surcharge?
0
Fedex International fixed surcharge?
4
Fedex International variable surcharge?
0
Show List Rates?
False
Insurance?
NONE
Residential surcharge?
0
Enable Envelope Rates?
False
Sort rates:
Low to High
Timeout in Seconds
NONE
Tax Class
--none--
Shipping Zone
--none--
Currency Code
USD
Enable Dimensions?
False

[autoparts4america]

I emailed FedEx for some assistance and and sent them the debug.
They emailed me back telling me that the system was actually sending FedEx information that the product in question was 2 packages of 46lbs with a total value of 195.2$ .

Basically Zen cart was splitting the value of the total weight in half and then sending that value to FedEx, since thats he weight of each package. Though it seems FedEx works with Total Weight of all the packages added together divide them by the number of packages.

So the quick fix solution was pretty simple from there on.
I went to includes/modules/shipping/fedexground.php
and in line 118 I changed

$this->_setWeight($shipping_weight);

to

$this->_setWeight($shipping_weight*$shipping_num_boxes);

since it seems that zencart runs under the notion of taking the total weight and dividing it by the number of boxes. This solution is working for us at the moment, we have used many different instances and it gives back the correct rate now.
Now I have to work on how to fix why google checkout crashes after the weight goes over 70lbs.