I've been considering installing Gear Vendors overdrive unit in my 2008 F-450 with 4.88 gears. Right now I'm turning about 2300 rpm @ 65mph. Can anyone give me the pro's and cons on the units. I checked with my Ford Dealer and they can change the gearing, but it voids my power train warranty, even with them doing it.

 

Do you tow? It's been brought up before and there's some conflicting information about GV O/D units and their proper use (or lack thereof) in a towing application...

 

I'm towing a5th wheel wt around 13,000 lbs

 

GV has max recommended 30,000# max GCVW for recreational use and 25,000# for commercial use. So basically it can handle 30k, but if you are pulling heavy every day then they say 25k.

I run 1500 RPM at 60 MPH with 4.30s and a GV...2000 RPM at 60 MPH without the GV. I have a 5th wheel pushing 18k. At that weight and stock power the tranny would kick down at the slightest incline with the GV engaged. However, it is great when unloaded on the highway for fuel economy. I now have my truck tuned and will reassess the towing situation on my next trip.

 

I have a 450 as well and was, considering GV.
Visited the factory and talked to the sales and tech reps in San Diego and this is what I found out.

1. GV was designed for gas engine stuff primarily. Diesel are hard ont eh GV equipment.
2. The OD function is recommended to be used in a no load condition the unit will not stand up to a diesel with a load. I asked about the loading, offered my 5K# slide-on as an example, the verdect was not in OD must run direct onthe GV unit.
3 towing, run direct will not withstand the torque loading from the diesel for long.
4. Hills, GV should not be used in hilly terrain and not on Big hills.
5. Big HP/Torque, again no go or at least it will not last very long.
6. The system is design along the line of an outboard cone clutch design and not been updated to handle the new vehicles.
7. Last but not least there was no intent to redesign to handle todays big power diesel as per my August 2010 visit.

I was looking to us their unit as a true auxilary gear simular to a big rig, but the real answer is not in a diesel. Now for their gas application it is ok to a limit. Also something of note to the 05+ ford guys, the output of the trans is a 34 spline shaft, the GV is designed to accept that input but the output shaft is a 31 spline unit. I was looking to add this between the Trans and the T case....

End of the day it was rather disappointing to discuss this possible application with them and they really did not want to even look at making any modification to handle the extra power.

My end solution is to go to taller tires and new rims..... ZF 6 speed is next.

 

^^^ That's some outstanding information right there...

Sounds like GV might be missing the boat a little bit by not catering to the diesel crowd...

 

My F450 had 4.88 gears, I took them out and installed 3.73.

 

Gear vendors also discouraged me from installing the unit on my 450.

 

Why not switch to (Rickson truck wheels was advertising here before) 20" wheels and larger commercial tires?

Bigger wheels = lower RPM's

Plus the new commercial tires are supposed to be good in the mileage department as well, plus last longer.

 

heli190 didn't say whether or not they have 4WD, which would add significantly to the cost of a gear change...

Larger overall diameter of the tires is a good idea too, but OTR-style/commercial wheels (like American Force wheels) and tires can be a real spicey meatball too. Either Diesel Power or Diesel World magazine just did an article on a Duramax used extensively as a tow vehicle that they installed similar wheels and tires on and their positive experiences with it.

Sounds like GV is pretty gun shy on diesels; I think regardless of the price differences I'd give the wheels and tires a shot first and see what effect that has, and then try regearing if you don't get the results you're looking for.

People here that are infinitely smarter than me can likely give you pretty much exactly what your RPM would be at a given tire size and gear ratio. I don't have one of those calculators handy right now...

Good luck!

 

Yeah but you benifit in several ways, as opposed to changing ratio or adding an overdrive box.

-tires last longer
-drop rpms
-more stable ride
-tougher tire
-No driveline changes
-Completely reversable
-safer, i imagine, for pulling real heavy stuff!!

 

I think you will find that the ricksons are 19.5 inch wheels and commerical grade tires. I had them on my F250, they are great for stability. The tires should last a long time. But if you don't get the tall tires the gearing won't change. As I recall mine ended up being the same size as my stock 16s. It's pricey also, I think I paid close to 3 large for the wheels tires, balance and trim rings on a SRW.

 

did you notice a mileage change on the tires alone?

 

3000$ is lots, but when you start talking about re-gearing or OD boxes, this is another viable option.

 

No, as I said the tires I bought were the same outer diameter as my stock 16,s.