I would like to know. can you get high geared rear ends for the P30 chassis? someday I would like to get a higher geared ring and pinion to get the rpms down a little. anyone ever done that?

Wit $$$$ You can put any rear end gear you want. Check with local rear end shops.

How many miles per year are you going to travel? The cost vs. paypack on gas mileage might not be worth the change. If you have replace the tranny then maybe it might pay back. I just had the tranny rebuilt on my SUV and it was $2700 and if I was going to do that on my MH it would take a long time to payback. I would leave as is JMHO.

You can do that, but if you go too far you will find the transmission downshifting to get the revs back up where they need to be, to have the horsepower for the speed you are trying to run.You won't know how much unless you have the tools and information (engine's power curve, power vs. speed curve for the RV) to do the chassis engineering. The P-30 chassis series came with different rear end gears (in some cases different axles) for different GVWR/GCWRs and applications (RV vs delivery van, etc). You should be able to find a different ratio for a GCWR downgrade.A couple of vendors offer add-on overdrive/underdrive systems, and in some cases know what they are doing.

NO YOU CAN NOT. OK maybe you can, but there are some serious considerations, that highly limit what you can do, or what benefit you will get. I'm going to make an assumption that if you are asking this question, that you are talking about a motorhome with a TH400. If so, you have a critical problem - TC stall speed. When I first dropped the 502 in my coach, I changed the gearing, because I had gobs of low end torque. What I found was, that unless the engine was turning 2500 RPM or higher, there was enough TC slip, that it had virtually NO impact on my mileage. So cruising at 55, compared to cruising at 75 or higher resulted in the SAME mileage. It was not enough slip to heat the trans, but just enough to hurt the mileage. The only thing changing the ratio did for me was forced me to cruise at a higher speed. You can just tell, especially with an engine computer and live display what is really going on. These vehicles are designed surprising well, in that TC slip, gear ratios, and weight are all designed to work together. If you change one thing, there is a domino effect, a whole series of other things that are no longer "in tune" with your change. The picture is bigger than just a personal preference of mileage vs drivability. BTW: You don't just want to change your TC to a lower stall speed, because then you will never be able to get rolling with the change in gear ratio. I hate to say it, but the only viable solution is going to a 4L85E which will give the acceleration off the line, and the low engine RPM in 4th with lockup. Still not sure that a older 454 will handle it. Maybe a late version Vortec can, but probably not the original 454 from the 70s and 80s.

Ring and pinion, No. You will need the low ratio at some point.That leaves you two options, newer model transmission with overdrive and aftermarket electrical control or a overdrive auxilliary transmission like a "GearVender". Both options will be expensive even doing it yourself!

P30 Chassis | Good Sam Community

shaneperch
Explorer
May 13, 2013
What was the mileage increase that you saw with the overdrive?
shaneperch
Explorer
May 13, 2013
Sorry for the double post. this internet connection went out and didn't see the first one . Sorry.
Daveinet
Explorer
May 13, 2013
shaneperch wrote:
sjholt wrote:
You might look around for a used Gear Vendor overdrive unit. It worked nicely in the P30 I had..New ones run $2700.
They bolt up to the turbo 400 trans, then all you have to do is shorten the drive shaft- about $120.

How much mileage gain did you see using that overdrive?
And that is the exact question I have, based on my experience with TC slip.
shaneperch
Explorer
May 13, 2013
I think the mileage I get on my Flxible versus the HR is comparable to the cost of diesel versus gas. So If I can get this HR up to 10mpg at 60 mph I would be grateful for that. anything in the single digits suck. I think my RTS was hitting around 9-10 on the flat. unladed weight on that is at 30,000 So if you start adding furniture generator tanks and all may be back where I am with the HR. frustrating. God I hope these fuel prices crash.
Daveinet
Explorer
May 13, 2013
I know where you can find 10+ mpg for cheap. There is a '78 Revcon in Colorado for sale for super cheap. It needs brakes, tie rods and front suspension wear parts replaced. If driven at 55 mph, it should give a very solid 10 mpg, assuming the engine is in decent shape. Its got the Olds 403 in it, so the mileage wasn't bad with those. I have no idea the condition of the interior, but if its typical Revcon, the upholstery will be worn, but the cabinets will be like new.
tropical36
Explorer
May 14, 2013
shaneperch wrote:
I would like to know. can you get high geared rear ends for the P30 chassis? someday I would like to get a higher geared ring and pinion to get the rpms down a little. anyone ever done that?

That's the last thing, I would ever do as it will affect more than top gear. Maybe with an overdrive transmission if you don't have one now.
You might consider adding your rig in your signature, so that your questions can be answered better.
sjholt
Explorer
May 14, 2013
I only got 1 mpg increase from 8.5 at 60 mph to 9.5 at 65 mph.
That was on a 32' chassis at 6.5 tons.
Up and down big hills is where the Gear Vendor shows its stuff.
I blew up the GV at about 100k miles on it. They changes from ATF to special Chevy manual trans lube(heavier weight but less than 75/90 gear oil) during that time I had the GV. If I had known that- It may have lasted longer.
GV has/had(?) a policy of exchanging a broken GV for a new one for $650.
I took the the one I blew up and I mean- blown up in pieces that the cases couldn't even be used and they exchanged it for a new one for $650...
I did use that GV really hard.
shaneperch
Explorer
May 15, 2013
Yeah I never thought of adding my rig info. I will try to do that. it is a Holiday Rambler Imperial 33 built in 1982. I also noticed that the windshield wipers are in fact hydraulic. I would like to get rid of that stupid set up and go with electric. I have air wipers in my buses and hate them. I want regular no nonsense electrical wipers. is that going to be a real tooth clenching frustration loaded job or is it fairly easy. Also while talking about this chassis I do have one problem, the power steering whines like crazy after about 20 miles of driving. how can Ifix that issue? It had power steering. but it whines.

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