4wd conversion gearing question....

[dbhosttexas]

The van. 93 E250 4.9L EFI. Mild naturally aspirated build estimated at 250HP, so roughly equivalent to later 5.4L output...

Camper conversion currently Sportsmobile RB11 more or less. I am using the MDF cabinets as templates for Poplar plywood / cedar replacements so dropping weight there. Will not be towing, so not super worried about weight, not disconcerned either... But let's put the weight concerns off to the side for now.

I am planning on a 4wd conversion via AJs 4x4 vans, but I am wondering what gears to go with that will make the 4.9 happy as fast as I am willing to drive a brick with a straight six...

I believe the AJs conversion specs 35x12.50s which is fine, so the plan is...

I know with my F150 4x4 5.4L 35x12.50/17s the 4.56 was just too deep and that poor V8 was running too high RPMs at freeway speeds to get anything resembling gas mileage...

AJs 4x4 conversion.
Either selectable lockers, or LSDs, I have had limited slips in the past. Are lockers are rough as I have heard? I will NOT be doing any radical rock crawling type stuff, but more snow covered logging roads type stuff, southern muddy "roads" etc...
Pro Comp Type 32 17x9s including spare.
35x12.50/17 All Terrain TAs, not making the mud tire mistake again, did that once with my pickup never again. Too loud, wear too fast, drive awful on the road...

[loper]

If you like the way it runs now, check the current tire diameter and gear ratio. Then use this conversion chart: https://tiresize.com/gear-ratio-calculator/ to match that with the new tire size. Or you can go up or down on gear ratios and the chart will show you what that does to your rpm.

You're going to end up with about 5" of suspension lift, plus the tire size difference. Sticking up in the air like that will cause some aero drag (less mpg). Mine was about 9" higher than stock after the conversion (stock with 29" tires to 5" lift and 35" tires).

With the weight and wheel base of a van, I don't think you will have any problems with lockers being rough. I have true tracks in both axles in my van, and the only bad habit it has is if I get rough with the pedal while turning, the back will come around a little. BUT...this is on slick roads and I have a V 10. And it isn't much, just steps out a little.

We did our 4x4 conversion at AJ's. Communicate what you want to Art and he'll take care of you. If you do have any problems, call him and he'll take care of it.

[dbhosttexas]

Originally Posted by loper

If you like the way it runs now, check the current tire diameter and gear ratio. Then use this conversion chart: https://tiresize.com/gear-ratio-calculator/ to match that with the new tire size. Or you can go up or down on gear ratios and the chart will show you what that does to your rpm.

You're going to end up with about 5" of suspension lift, plus the tire size difference. Sticking up in the air like that will cause some aero drag (less mpg). Mine was about 9" higher than stock after the conversion (stock with 29" tires to 5" lift and 35" tires).

With the weight and wheel base of a van, I don't think you will have any problems with lockers being rough. I have true tracks in both axles in my van, and the only bad habit it has is if I get rough with the pedal while turning, the back will come around a little. BUT...this is on slick roads and I have a V 10. And it isn't much, just steps out a little.

We did our 4x4 conversion at AJ's. Communicate what you want to Art and he'll take care of you. If you do have any problems, call him and he'll take care of it.

Yeah, and I figure my 6 coffee cans slugging up and down won't be as likely to get the tail whipping around behind me like that V10... I am NOT aiming for a hot rod by any means. I am looking for RELIABLE and comfortable. MPG concern is more for range than anything else. I am not under any impression a lifted 4wd brick will give me 20+ MPG after all, But if I could stay in double digits I would be happy...

I am planning on a Velit gasoline heater instead of the typical Chinese diesel heater, and tapping off the main fuel tank. That way I have a common fuel source. Van runs off gasoline. Furnace / heater runs off gasoline, my old Coleman stove, runs off gasoline, my old Coleman lantern, well stays at home because I have battery powered LEDs now but that is a different conversation...

Last propane appliance I have is the instant hot shower / water heater. I CAN heat a pot of water on the stove and pump heated water to the shower head but not interested in doing that... And a Thermacell which runs off of isobutane canisters.

[loper]

Gas mileage is not my van's strong suite. Bone stock, with 4:10 gears and 29" tires I got a best of 15 mpg on a road trip, running mostly 70 mph (speed limit).

With the 4x4, lift, 4:88 gears, 35" tires and a roof rack I've had a best of 13.25 mpg, average about 11 mpg, running 65-70 mph. If I start pushing it past 70 the mileage just craters.

[dbhosttexas]

Originally Posted by loper

Gas mileage is not my van's strong suite. Bone stock, with 4:10 gears and 29" tires I got a best of 15 mpg on a road trip, running mostly 70 mph (speed limit).

With the 4x4, lift, 4:88 gears, 35" tires and a roof rack I've had a best of 13.25 mpg, average about 11 mpg, running 65-70 mph. If I start pushing it past 70 the mileage just craters.

4:88 seems awfully deep geared for highway driving, even with 35s, but YMMV as they say... And I would be thrilled at 13.25 MPG after a 4wd conversion.

Factory tires were 29.29" diameter, currently installed tires are 29.53", and oddly enough same brand as I am running now although I will likely go BFGs, but let's say I decide to go more budget friendly and throw a set of Venom Power Terra Hunter XT 35x12.50/17s on there, 35.53" diameter, BFGoodrich All Terrain TA KO2 in that same size has a diameter of 34.5". Nobody can make a tire true to size I guess...

I know the Terra Hunters are not three peak snowflake rated, but I don't live in 3 peak snowflake rated areas... I've seen how they do in heavy snow on and offroad and they will work just fine for me. But I would prefer the BFGs...

The BFG from 4Wheel Parts goes for $374.99 each. $1874.95 for a set of 5 (Matching spare)
The Venom Power Terra Hunter XT from Giga Tire are $204.46 each $1022.30 for a set of 5.
That is a difference of $852.65.

Not insurmountable, but not pallateable either, especially given the rumored quality control issues BFG has been having lately...

[1der]

35.53/29.53 = 1.20
4.88 / 1.2 = 4.07 equivalent.

Rpm at given speed will be about the same, even a tad lower than the 4.10 & 29.53 combo by going w 4.88 & 35.53. The 4.88 & 34.5 will be a bit higher rpm since it equates to about 4.18.

If you are happy with the rpm's vs speed you have now then 4.88 gearing would be the way to maintain that.

One consideration is if you want a locker, or a particular locker. Some gear ratios are hard to find lockers for.

Our setup is for winter roads - LSD rear and air locker up front. I would not want a rear locker for snow or icy roads. And you have about as lightweight a van as can be had plus putting that on 35's.

[dbhosttexas]

Unfortunately the van is in the shop until early / mid week next week (Radiator replacement / Trans cooler lines were leaking, and replacing tensioner, and AC compressor as both were very obviously having offended bearings.) I have no idea what the OE rear end ratio is. I suspect it is the original factory installed gear set. What online searches I can do / find looks like the ratios available in 93 on the 6cy E250 were 3:55 and 3:73. I kind of think possibly 3.73 might be installed. Will check once I get the van back from the shop... I have upsized the tires from 225/75R16 to 245/70R16 so difference in diameter is .1"

[1der]

If the axle is all original then have the shop send a picture of the driver door jamb factory sticker. The axle code is on it. You can do a search for the code to determine ratio and LSD / Open.

https://www.blueovaltrucks.com/tech-...-door-sticker/

Sticker example:

[1der]

If 3.73 is gearing, then 4.54 will be closest new gearing to equate to the 3.73?gear/29.53 tire combo .

[dbhosttexas]

Originally Posted by 1der

If the axle is all original then have the shop send a picture of the driver door jamb factory sticker. The axle code is on it. You can do a search for the code to determine ratio and LSD / Open.

https://www.blueovaltrucks.com/tech-...-door-sticker/

Sticker example:
Attachment 48961

I saw that page you got the image from, and I have the door jamb sticker photo from when I bought the van. It is axle code 24 which from that lookup shows a Dana 60 with a 3:73 gearing and open diff...

That is a LOT of differential for a straight six!

I think you are right whomever mentioned the 4:56 ratio for 35s,

Now that I know it has, or at least SHOULD have a rear Dana 60, new related question... And I think the answer is yes but I need to verify this.

Can the 93 Dana 60 be converted to the 8x170 bolt pattern / rear disks of the later model Super Duty configuration? I would think starting with my existing housing would help constrain costs at least a little bit... As I understand it the 4wd conversion uses the 99-up front Dana 60 with the 8x170 bolt pattern and, well it would be stupid for front and rear axles to have different bolt patterns...