Reality check, is the World American brand part RING AND PINION GEAR RA351-355-472 3.73 RATIO

[TaliaDPerkins]

The same fitment and function as as the Dana/Spicer part 597237C91 ? The goal with an MD3060 is to cruise at 1538rpm in 6th at 75mph on 10R22.5's . . .
. . . and if the 210hp 3126B won't push that hard (I know it won't up a grade), I'll see to uprating it. No forward sharp corners on the RE Thomas, but 1 foot radius curves, so it should be more aerodynamic than pushing a brick.

And "World American" seems to have good reviews -- does anyone know if those are astroturf?

 

[TaliaDPerkins]

It appears a 275hp ~ 300hp will be required to tow a trailer with a 4WD/AWD small sedan like a Subaru Legacy at those low rpm.

 

[magnakansas]

Aerodynamics, it is mostly about the back end. Some about the stuff hanging off the roof, sides, and bottom. Least is the front. I think the 1500 rpm cruise, might work, but headwinds, up grades - even little ones- you will have to down shift and move the engine rpm closer to 2,000 rpm. I expect 4th gear is where you are likely to be up or down those 5,6,7 percent grades you will find in mountainous roads. I would advise 4.10 or 4.30 gears. And let the engine spin up a little more.

 

[TaliaDPerkins]

The goal was to do 75mph on the level while towing a trailer, with the RPMs down for better mileage. Raising hp from 210hp @ 2200 seems required. I need more like 220~260 in the 1550~1750rpm range, and a final ratio that balances out for power made and needed at 75mph.

In fact, I can find an 4.1 J230-SB axle available . . .


Thank you!

 

[TaliaDPerkins]

Well, this is what I received. A box inadequate for the task, which box was falling apart on receipt. One layer of cardboard and some oiled/waxed paper had been separating the parts. The gears had banged into each other, I'm fairly sure someone dropped or threw the box from some height. I will ship these back and they will try again.

 

[Ronnie-SKO]

I have a Thomas HDX 2005 with a 210hp Mercedes , and 3060 trans 6.17 rear. It struggles to pull a trailer at 70 mph. 75 is max speed at 2500 rpms, in 6th gear. With a trailer basically it is impossible to reach 75 without a tail wind or without a slight downgrade. Also wind noise is much greater at 75 then 70.

You are going to burn fuel doing 70 or more, and 1500 is lugging it. I would put an exhaust gas tempature gauge on it. EGT's go up when the engine speed is too low for the load.

 

[TaliaDPerkins]

If I am using this website correctly: https://www.tritrack.net/horsePower.html
Then using pessimistic numbers:

And this:

https://www.blocklayer.com/rpm-gear

And using these engine spec charts, then the 210hp @ 2350rpm with a 6.14 rear (what I have now), should let me do 70mph (the local interstate maximum) at 2350rpm. Before I put a trailer on it I can use it alone and a small scooter as needed.

The plan is to drop ~$15k into my forever home (until it's that last home with a diaper and drool cup) and drop the ratio to 3.73 and put in a 300hp Cat 3216B. This should let me cruise sipping fuel (relatively) at around 70 ~ 75 mph in 6th, if only barely, if I hit those pessimistic numbers. I think from reading more likely numbers are 28kbs with a faired in toad, drag coeff = 0.75, and rolling resistance numbers of 0.006 -- and the 300hp at just ~1515rpm will put out more than is needed to go 75mph. I may end up hating life in 5th gear with the 3.73 and changing that out for a 4.10 diff.

I'm basing all this off of Cat saying the best mileage and engine life is at lower rpm. If EGT in 6th goes over 1325 ~ 1350 degF, I will shift into 5th. If it gets too high in 5th, then to 4th. Peak hp is about 2200rpm, I don't see much point in going over that ever.

But if I have the ideas or math fundamentally wrong (or the websites do) then I am here seeking input.

Thank you!

 

[magnakansas]

EGT, I advise 1275 maximum. This is mostly about exhaust valve temperature and long life. When EGT gets close to the maximum EGT, down shift and bring up engine speed.

William

 

[TaliaDPerkins]

So Cat says 1350degF EGT is fine, but they want to sell replacement engines?

I've really been wondering if Cat's advice about low rpm (1440~1800) = best mileage is correct, because so many people seem fine with running at 2400rpm ?

I do begin to think a 4.1 is a better ratio. I dunno.

Thank you!

 

[Ronnie-SKO]

Your power numbers are about right, I did the numbers on mine and came up with about the same, and real world experiance confirms it. 1350F seems to be pushing it, most do not recommend more then 1200F, and I have seen rings get weak/ lose tension from 1350-1400 for any length of time. In terms of mileage running at peak torque is best. I can see running 1800 but not 1500rpms. I know My Mercedes 906 would be happy at 1800-2000 for cruising if it made enough power at that speed. The engine is rated for more then 210, it actually says 260 on the valve cover. A freind has connected to the computer and verified it is actually set at 210. I should send the computer away and have it set to 260, it would be so much nicer to drive with a little more power. Really love everything else with this bus. The little green bus (in my avatar) is more of a work/hauling bus

 

[TaliaDPerkins]

"In terms of mileage running at peak torque is best."

And if the charts are right, that rpm for peak torque is the 1440 they say it is. But, any lower gearing and I definitely will not have the power to move at interstate speed at that rpm while towing a trailer. Any time I climb a grade or have hilly country, I have no doubt I'll be leaving it in 5th, or even taking it to 4th. Some place like Sandstone Mtn. on I-64 (7% grade for 7 miles), I'll have to wait and see what happens, watching the EGT.

My parents are moving into an assisted living facility just West of Charleston, WV, I'll be doing that one a lot.

 

[TaliaDPerkins]

If a file upload is all your engine needs to be 260hp from 210hp, I would definitely do that.

 

[magnakansas]

Best mpg, yea agree lower engine rpm. But, probably not able to do that going up an incline. Most folks like me, transmission kinda dictates 2400 rpm flat cruise, 55 mph. I have 545 transmission. Great for in town driving. Terrible for highways. I get 10.5mpg - 12.5 mpg now. I expect to get 12.5 mpg- 14.5 mpg at 60mph with the change to an Allison 2000 series transmission 5 speed. I am 17,000 lbs. 4.3 rear gears, 10R22.5 tires. With the rear gears I have I think I would not be able to use the 6th gear. 7852077600 if you want to talk about gears and stuff.

William