1999 GT Vectra 39Y. Can you upgrade drive train

Duracell · 01-25-2021, 05:03 PM

Hello Folks

I purchased a 1999 Grand Tour Vectra 39Y and we love the motorhome. The only issue I would like to address is it is under powered. Would anybody know if it is possible to either supercharge the engine and change the transmission. Or are there any other options to address this issue. Could I change out the drive train or is that even possible?

Thank You

Duracell

neub · 01-25-2021, 07:49 PM

Need a little more information...is the chassis a workhorse (GM powertrain) or the Ford F53 chassis?

tderonne · 01-25-2021, 09:15 PM

It's a Chevrolet P12 chassis. 454 engine, Allison 4 speed trans without overdrive.

Duracell · 01-25-2021, 09:51 PM

Me not very educated in theses matters your help is greatly appreciated

Duracell

neub · 01-26-2021, 06:06 AM

The allison transmission is an excellent unit, no changes needed. Supercarger or a turbo not advisable due to cooling issues. Your best bet is to improve of breathing of your engine. The go to for most is Banks Power https://www.bankspower.com/c-82-vehi...%7Cyear%3D1998

Duracell · 01-26-2021, 07:46 AM

Thank You Very Much. Will get this done how much power increase would this create? You are a life-saver.

Duracell

Morich · 01-26-2021, 08:27 AM

Several things that make me say this is not a good option. One is the expense is too great on an RV of that age.
Consider that the option to upgrade has been around for more than twenty years and nobody has done it, so does that mean that it did not bother others or does it mean they considered it and rejected the idea?

That is a pretty big unit for a gasoline powered engine but the added performance is not enough to make me add that amount of money to change out the major parts.
I've learned to drive slower when I had a like situation.

MinntoMich · 01-26-2021, 09:03 AM

A little reading up on the P12 chassis tells me that it is similar to a Kodiak or TopKick truck chassis and the Workhorse designation is W20. There is a dearth of information on upgrading this but if its similar to anyother 454 plant in a GM class A then an exhaust manifold upgrade should be possible. I've thought about it on my 93' and have found that most recommend not installing a lower priced setup. That's up to you I suppose but for a decent YouTube video on how its done surf the "Camping with the Kellys" channel.

Don't know your location or the mileage of your unit but after 30+ years in a northern climate I know enough to be real tender taking an exhaust manifold off.

Good luck on whatever you do. The advice to drive slower is sound and won't cost you a dime in upgrades but at some point in the future you will be replacing an exhaust manifold gasket. Maybe that would be the time?

neub · 01-26-2021, 09:04 AM

You will get about a 10 % gain but you got a big rig. Our previous gas rig was a 1995 ford 460 ( with no modifications) which had good power but the coach was 9 feet shorter than yours

al1florida · 01-28-2021, 04:57 PM

Don't overlook the fact that you are driving a rig that weights 22,500 pounds with a gas engine.

I doubt you will get more than a 10% gain in power, not matter what you do with a reasonable amount of money. I don't think that is enough to matter all that much.

It would be best that you are not going to have jack rabbit starts and you will slow down on overpasses and hills.

The engine and transmission along with the rear axle gearing will take you up and down mountains just fine, however it will be slow and in third or perhaps 2nd gear with the engine making lots of noise.

Bo Walker · 02-01-2021, 03:06 AM

I would try having a mechanic tweak the timing. I had a 1996 Winnebago Adventurer with the 454. It was only 34 feet long. The engine was a powerful engine. But tweaking the timing with the distributor helped a lot. I towed a Saturn Vue most all the time, sometimes a Jeep Wrangler. Long high hills made the engine suck air pretty loud. Sometimes, it would slow down to 35 mph on hills when I was nearing Cherokee, NC. It never gave up on me.

Rick 99037 · 02-01-2021, 09:14 AM

When driving any RV, once we are past diesel VS gas engine issue, it comes down to tradeoffs in their use. In 1999 the GM 454 was a powerful gas engine, and being fuel injected, and as I recall having a powerful electronic ignition system; a reasonably efficient engine too. No doubt, it came with a cam designed more for torque than RPMs. You want that. In RVs, the 454 was a very popular choice. But as you know, it always comes down to weight to horsepower ratio, and after that, your willingness to sacrifice MPG for speed. Make sure the air intake supplies cool outside are to the engine. That's free horsepower. Adding automotive headers improves breathing, and might give you 20 horsepower for a modest cost. But you need to cultivate a different mindset than you had with your car or pickup too. You may be used to pulling that steep hill in your pickup at 70MPH, but the horsepower required, to pull a heavy rig anywhere near that speed could well be 35% more than you have, reduce engine life, and reduce you to 2 or 3 MPG. There's just no free lunch. All at the end of the day, if you could; you'd shave of 20 or 30 minutes on the day's trip.
If you are like most of us, you've already discovered keeping under 65 MPH, and not slamming your foot to the floor on hills makes a drastic difference at the pump. Now live with your limitations, and that you're not driving a car, and too, that you will irritate people that don't know the difference; And think when it says the speed limit is 70, every vehicle on the road both could and should be doing that speed.
I also get personal satisfaction from returning the indignation of other drivers, with a smile and friendly wave - with all my fingers - I might add.