Christmas has arrived again at our house with an exciting gift— a Gear Vendors Overdrive unit! Okay, maybe it wasn’t Santa, but in our ongoing mission to enhance our motorhome, we decided to invest in better fuel efficiency, a smoother ride, and reduced wear on our 454 engine paired with a TH400 transmission. Based on my rough calculations, this $3,500 upgrade should pay for itself in about three years, considering our average mileage and current MPG.

Has anyone in this group installed a GV unit on their vehicle? If so, do you have any tips or concerns? How has it performed for you?

Thanks,
Peter

Peter

I have installed hundreds of these and had them in every truck that I pulled trailers with until the Allison came out in the Chevy. They are worth every dollar you spent for it. Simple to install and very effective, cruising RPM will drop by 600, engine driven accessories will live longer due to lower RPM, your 3-Speed transmission is now capable of six-speeds, everything good!

Take your driveline to an experienced drive line shop to shorten and rebalance.

They used to recommend the GM rear axle lube for the unit, with all of the advances in lubrication technology, I don’t know what is recommended now. If it’s not specified in the manual, call them, the clutch inside thrives on good friction, you don’t want to screw that up. The shimming of the input shaft is CRITICAL too.

We are on our way to church but feel free to call me anytime with any questions that you might have.

Good luck and enjoy!!!
Billy
337-241-5033

Peter, never had one or installed one, but always thought they were a good Idea. When I had seals put in my TH400 the rebuilder said that the Gear vendors overdrive was the way to go. The cost in my case is payback, it is low, I drive 71 so few miles a year it would take at least 10 years.

Sure, will be interested to get your feedback after a few trips.

Of all the things I did to my Regal, the Gear Vendor modification was always high on my list but never got done. I am interested how it goes for your coach. Keep us posted please!

I believe you will love the overdrive .

Thank you for your responses, and special thanks to Billy for your advice and offer to help. I'm waiting for the weather to warm up a bit here in Wisconsin before tackling this project. I’ll be sure to share an update on performance, as we have a road trip planned to the Canadian Rockies and Montana while towing a Jeep CJ7. Hopefully, we'll see better mileage this time since we only got around 5 MPG last year.

Peter
I installed one in our 89 regal a couple of years ago. It came with the regal when I purchased it. I have no clue as to the mileage before the install and I have only checked it once afterwards. On a trip from Asheville NC and Charleston SC it got 7.65 miles per gallon towing a Jeep tj.
Check the alignment of the drive shaft after installing, I had to shim the transmission mount about 5/16 to correct. I used large 1/2 fender washers, slotted so they would slide in. As a side note I have not installed the controller, I just wired with a toggle switch, forward on-back off.
I think you will notice a lot less engine noise in overdrive, and will be surprised with the way it preforms.

br

Thanks for the reply!

I also had my eye on this for my 24 footer for the same reason, but many folks on other forums said it doesn't really do much to increase fuel economy on these platforms. I read that there used to be a blurb on GV's website that said something along the lines of "if you're looking for better fuel economy, slow down". But the reduced RPM, and thus noise, at cruising speed might even still make this worth it for me.

P&J please let us know how it affects your mpg numbers with and without a tow load.

It will be going in soon. We will have reliable results in May after our first longer trip.

The results are finally in! Sorry for the delay in posting, but here’s the full update.

As a quick recap, before last season my 1988 Regal got some major upgrades — most notably a **Holley TBI fuel injection system** (replacing the old, tired carburetor) and a **Gear Vendors overdrive unit**. Since completing the upgrades, we’ve put about 4,000 miles on the coach, including a trip from Wisconsin to the Canadian Rockies.

I drove the motorhome solo out to Montana to pick up my Jeep CJ7, and from there on I flat towed it for the remainder of the trip. For roughly three-quarters of the journey, I was still dialing everything in — adjusting timing, fine-tuning the air/fuel ratio, and learning how to best use the Gear Vendors overdrive.

Before the upgrades, I was barely seeing 5 MPG. Over the entire Canadian Rockies trip, I averaged 6.7 MPG — and that includes all the mid-trip tweaking. That’s over a 25% improvement.

On the return trip home alone, the average jumped to 7.2 MPG — more than a 30% improvement.

Then in the fall, back home, we logged a few hundred more miles visiting State Parks (no Jeep in tow). For those trips, I averaged exactly 8.0 MPG — a 37.5% improvement over baseline!

But beyond fuel economy, the drivability improvement has been huge. The 454 now purrs much quieter at lower RPMs. Cold starts are effortless, no more idle fluctuations, and it’s incredibly easy to select the right gear combination — especially on hills, both up and down.

I couldn’t be happier with the results and highly recommend both upgrades.

Are we done? Not even close!

Next up, once the weather cooperates, I’ll be "addressing" the AIR emissions system and installing Hedman 69820 Elite full-length headers.

Wish me luck!