I am debating weather it's worth the $750 to get my Gear Vendors rebuilt. Anyone have any before and after highway mileage comparisons? I know it's diminishing returns because of the high C/D, but I'm curious...
Mark

 

I got 17 before overdrive with my auto, driving it nicely. Now with the getrag, I pull 21-22 flying through the gears.

 

I sorta meant add on overdrive units (or double overdrive in this case).

 

If you have 4.10s, I'd get it rebuilt. If 3.54s, it's probably not worth it. I know a TDR member who added a Gear Vendors to his 3.54s, and didnt gain more than about 1/2mpg, if that. But, at 70mph, if you drop from 2050 rpm to 1650, it puts you below the optimal BSFC curve, netting a gain of zero.

DP

 

If it's a gear vendors it can be replaced for 25% of cost. I love mine and I'm also getting about 22% less engine wear. I have the 4:10's 4x4 so I figure in overdrive unloaded at 60 mph my gear ratio is probably 3:40 as I'm turning about 14-1500 rpm; normal was 2000 rpm, and the noise reduction is amazing with the 4" exhaust. Also at this speed I can easily average 23 mpg on mostly highway mileage.
I originally bought it to help with my 9500lb (dry) 5th wheel and this gave me in between gears which really worked out. Now 160,000 miles later(2000CTD) the splitter and truck are still running strong.
Jerry

 

I have 354 gears, but if I can drive 80 and get the same economy as I would at normally achieve at 65, that's bonus. Our speed limit is 75 here in the land of entrapment.
I don't know if this is a realistic goal though, because of the aforementioned terrible coefficient of drag of a 4x4 1st gen.

 

TANSTAAFL - There Ain't No Such Thing As A Free Lunch.

You're right on with the brick observation. Save some bucks and just go with the 3.54s.

Regards, DBF

 

I'm going to open the unit this winter and see what it needs. If it's just the clutch I will try to get my machinist friend to trick Raybestos into letting him buy the connical friction clutches and do it myself. I already had the driveshaft made, so I want to give it a try. If nothing else I will have the gear splitting!

 

I wish I had a GV with my auto. I'd leave it in 3rd and use the GV when towing heavy. I think the tranny would run cooler.

 

Yeah, I have to agree with you there. That would be kind of nice.

 

Why would the tranny run cooler- the engine would be turning about the same RPM, so you end up with the same sloppy convertor function, whether you are running in OD/ direct or 3rd/ over. It isnt the loads in themselves that burn up the OD on the tranny, it's normally the low RPM (and low line pressures that come with the RPM) combined with the heavy loads. If you turn 2200rpm down the road, the tranny is more efficient than if you are turning 1700rpm at the same speed. I think that is why the one auto I had did so well towing in OD- I went 75mph everywhere I went, taking my RPM up to about 2100. Everything was nice and tight by that RPM.

mhuppertz- I'd put it in; at least you'll have more gears to choose from at in town speeds. To see how much MPG improvement you can get, drive 65 for a while in 5th, then do that same stretch in 4th. If you get a 3-5mpg difference, it would be worth it. I still think at speeds above 70, wind drage has a bigger and bigger effect.

Daniel

 

It might run slightly cooler because the OD section wouldn't generate heat, but I agree with Daniel that the TC is the main source of the heat. I wouldn't add a GV just to keep trans temp down.