Walter

[Master Yota]

Doesn't optimal rpm also depend upon manifold pressure?

Like I said earlier, a whole host of different variables; cam choice, valve duration, vacuum, timing, etc... The primary function of the gearing/rpm table is give a builder options on gear selection. And its a two way street, a builder can either build the diffs to accommodate the engine, or vice-versa and pick a cam choice that best matches the gearing and tire size. The info in the tables however is not written as an absolute fact. Its more of a guideline than anything else.

In reality, and M37 isn't really any heavier than any other full size pickup, and its actually quite a bit lighter than the current crop of modern trucks, so really deep gears aren't needed for modern power to move the truck. But gearing is needed to overcome tire diameter, and the extra mass/resistance of larger tires, and to provide some feeling of control. Regular old 4.10's will spin a 37" tire without much issue, but it'll be a dog off the line, and shifting will be a necessity to keep it moving in the hills no matter what engine mods are done.

Just for amusement, with my 4.56's and 1100:16's I can just about hit 50mph in 2nd gear if I wind the 428 out to about 6000rpm. It sounds awesome, and sure puts punk kids in their place when I wanna' play "stop light to stop light"...

[tbone1004]

Jim, it absolutely depends on manifold pressure, but my rationale when doing that chart was looking at rpm combinations in similar weighted trucks running similar size tires with the same cam as my engine. They might have been a couple hundred lbs lighter being broncos, but the same was said about the f250's which weigh more. They were all saying that optimal rpm for these was anywhere between 1800 and 2400rpm with certainly engine combos liking some range in there.
For me, here are some ideal speeds that are commonly encountered
25mph-neighborhoods
42mph-side roads
52mph-main roads
62mph-highways
72mph-freeway

Without really really high gears in the diffs and custom gearing in the tranny, those 5 speeds aren't possible. The closest for me looking at the chart, is using the 4.10's.
25 isn't going to happen, but 20 is still ok in the neighborhoods and in 2nd that puts me at 2200rpm, and 30 in 3rd puts me at 2000rpm.

42 is the bitch because it's 2800 rpm in 3rd, and 1600rpm in 4th, so 4th will be ok on the flats and I'll have to wind it up a bit more in the hills. Don't really sit at that speed very often though, and 52 is just shy of 2000rpm in 4th, so that'll be a bit better.

62 is 2300rpm in 4th which is good, and 1700 in 5th on the flats, and 72 is 2000rpm in 5th.

The CUCV ratios knock about 5mph off of each of those speeds so the engine would be revving a bit higher than it really needs to be and 4.10's should still be enough of a reduction to give me enough torque to move the HMMWV tires. Diesel ratios on the transmission would make the jump from 3rd to 4th a bit better but lose some of the granny in the granny gear. I really wish I had been into this hobby prior to all of the 1100r16's getting gobbled up. Would love to have a set of them, but it seems like the HMMWV tires are the only reasonably priced way to get above 35" without going to a semi type tread which would just look funny on this truck. I wish the DuraTrac was available in large sizes, but no dice, biggest they go is 35.4 in a 20" rim which just isn't right. Too short for that width, and a 60 aspect ratio doesn't have enough sidewall to look good, and are also over $400/tire.

[JimC]

I kind of like the 41" directional Interco's though I wish they were narrower.
For me, the surfaces I'm interested in are riverine sands, cotton patches (now mostly soy bean fields), slough crossings, and gumbo. I hate gumbo.

[tbone1004]

yeah the interco's are nice but the tread is too soft and isn't a great pattern for on road driving.
http://www.trailworthyfab.com/Stock-12- ... TIRES.html
$235 for 12 bolt rims with runflats and tires ready to go, can't argue with that. They aren't 100% new, but can't argue with the price for tires that large. The MT/R's are pretty nice too but I think the BFG's will behave better on the street and wear longer.

[JimC]

That's a good price. Hope shipping is reasonable.

I'm not worried about roadability. In the 52 years I've owned my 37, it hasn't done enough on-road driving for it to be a consideration.

[Master Yota]

Interco makes a lot of different sized tires that are available in more than just the usual Swamper pattern. The STS is an all-terrain type pattern that is available in both radial and bias ply versions and is pretty popular in the Mall Crawler crowd. The downside with H1 wheels is that most tires for a 16.5" rim are being phased out and are getting difficult to come by from any manufacturer. Expect 15 and 16" tires to follow suit as the world stupidly marches on with low profile tires for trucks.

There are a lot of manufacturers who make larger radial tires; BFG, Mickey Thompson, Dick Cepec, Hankook, Pit Bull, Toyo, Yokohama and a few others that I'm forgetting. Also, if you haven't considered it yet, these guys https://www.treadwright.com/p-81-37x12- ... g-m-t.aspx have had great reviews on their tires, and they are pretty affordable.

[tbone1004]

I am well aware of treadwright and they are an option I'm considering, but I still think the HMMWV BFG's will have better tread life.

I know about the rims being phased out, but I think the HMMWV tires will be around for quite a while yet to come, at least until the DoD phases the vehicles out. Most of the other guys still top out around 35 inches though and I think it is just too small for an M37. I see all of the rebuilds that Charles has done, and the Yoko's that he's putting on there, I totally understand that they're the only real option that plays nice with the stock rims and what not, but I still think they just look too small.

The 1100r16's have a badass tread, wear like iron, and look incredibly badass on the truck and I'd kill to get my hands on a set of them.... will keep hoping I get lucky. I'd grab a set of the 325/85/16's that replaced the 1100's but it specs a 9" minimum width on the rim and 6.5" is a far cry from 9...

[Master Yota]

BFG's are a long lasting tire for sure. I've currently got a set of KM's on my DD, and I've logged at least 10k miles on them without any noticeable wear. Amazing for a mud terrain tire.

If you're heart is set on the 1100:16, you may find it easier to get them from us Canucks up north. Try these guys for a price and availability...
http://www.kijiji.ca/v-tires-rims/vanco ... nFlag=true

The 325/85/16 is the one you want...

Just in case anyone is interested, this is the gear ratio and tire size chart that I use: http://www.4lo.com/calc/geartable.php

[JimC]

For somewhat sentimental reasons, I like the look of the old directional Firestone Super All Tractions. I wish they were still available.

All this talk of tires makes me really miss the old days when Mohawk Rubber Company used to give me free 9.00x16 tire sets for my 37. Between that and the Sheriff's Dept paying for the gas, life was easy. :-/

[tbone1004]

Ray, my only concern with the 315/85/16's is until I can swap axles, are they going to be ok on the 6.5" rim even though they call for 9"? Until I can get better brakes/ratios and what not I have no intention of going much over 55, so if I behave and do the chalk rub to find out optimal psi to prevent crowning would they be ok?

[Master Yota]

Ray, my only concern with the 315/85/16's is until I can swap axles, are they going to be ok on the 6.5" rim even though they call for 9"? Until I can get better brakes/ratios and what not I have no intention of going much over 55, so if I behave and do the chalk rub to find out optimal psi to prevent crowning would they be ok?

I don't see why not. Were talking about a difference of 1.5" per side of the wheel (in rim width). In reality, its nothing to worry about on a tire that tall. There is easily enough sidewall flex to accommodate the narrower rim without issue. If it was a shorter tire, like a 33 I wouldn't recommend it, as the tire would crown terribly, and be god-awful to try and mount...
For on/off road use, my personal preference is to run a rim that's at least 4" narrower than the tire. IE I currently run my 36x12.50x15's on 8" white spokes on my trail rig, although the manufacturer recommends a 10" rim. I've run these tires for the better part of 25000 miles on 4 different trucks on the same width rim, and never had an issue, and the tires are wearing nice and even across the face. My trail rig is still street legal and still logs about 3000 miles a year on the highway now that I no longer use it as a daily driver.

[tbone1004]

score of the century yesterday. $230 got me an ALC F-1100DM pot blaster, and an Eastwood somethin somethin blast cabinet with foot control. Missing the hoses and a tip for the gun, but has the gun and pedal so winning there and the hose coming out is for the pot blaster gun. Was going to buy the HF 40lb cabinet but found these on Craigslist and hot damn was that a score after finding out that the pot is $650 new...

[tbone1004]

Was planning on running dual alternators for a deep cycle/house system, but was randomly checking my amazon wishlist and the blue sea ACR was on sale 75% off a long with a bunch of other small system that I was planning on getting.
http://www.amazon.com/Blue-Sea-Systems- ... B001VIXLRO

With this newfound change, my electrical diagram will have to be adjusted a little bit since I was planning running one system for ignition and lights, and tie the other system into a deep cycle battery from a separate alternator and now it will just be one charging system. I've had a NOCO Genius battery charger hooked up to it, and it is a brilliant little charger for offboard charging
http://www.amazon.com/dp/B00CBTRMZ4/ref ... EV9GD9PWP8
At some point I'll grab one of those and mount it in the battery compartment and use
http://www.amazon.com/NOCO-Genius-GCP1- ... =noco+gcp1
that to easily connect it to shore power.

Should be fun to get some more of the electrical stuff going. The blast cabinet I got didn't come with a siphon and I tried using the pot blast last night but it moves too much air all the time so it wasn't really a great option even though the PO had it run in there. Ordering the siphon tube and hopefully will start blasting things slowly but surely



Edit: So much for the above, just got a cancellation notice by the seller. bollocks

[tbone1004]

sand blasters are a wonderful thing. It's slow going because I don't have an aggressive media in there right now, but it's definitely progressing which is good. It's going to be so much easier to put back together new looking parts than it was with the sketchy red paint job and a bit of surface rust everywhere. Doing the light buckets and the gauge panel now just because they are out. Engine parts will be next and since the pot blaster is here, I think I'm going to tackle the front fenders once it warms up outside. I know they're really bad, but with the patch panels not being available right now I'm going to have to get creative to replace that panel ahead of the headlight. Definitely going to put a drain hole in there on the new ones to make sure this doesn't happen again those edges are really really nasty

[m37jarhead]

I used to use Black Magic in my blast cabinet. Worked fine but now I'm using an 80 grit media that is copper colored.
The texture left by the 80 grit is about right for priming and painting. I buy it in 40 lb. bags from a local blast media
supplier. Don't remember the exact price but it is fairly cheap. And it's not as "dirty" as black magic.
Jerry