Rear end swap starting.

[yourpc48]

Recently I had some brake issues with my P15 and while I was under the car with the wheels off I measured from drum to drum 61 1/8 roughly. So Monday I went to the wrecking yard for a couple hours and measured out some axles. I had seen some threads about the Explorers so I measured them out. Earlier drum models seem to measure out to roughly 60 inches and the newer 95 to 2001 with disc brakes is about 59 1/2. I will be picking up one with discs in the morning. I found a yard that quoted me half the cost of other yards in the area. Its a U-Pull type yard so I will do my best to get all the hangers and it looks like the sway bar may also work with some mods if it clears the tank and such. I just want to get the rear end before the guy changes his price up towards the other yards prices. I will have a good stock rear end for sale soon. Anyone need a rear end? It is good and quiet. It leaks a little from the pinion seal but the axles were dry the last time I looked. Make me an offer. I also have been trying to look for brakes for the front that are newer than the 78 volare sets that have been out there since at some point they will be harder to get. They are an order item only from my NAPA now. I found that the 2001 Explorer I was looking at had a rotor that came off the hub and the calipers look like they would adapt easily to a cut metal plate mounted to the front spindles so I am going to get a set of calipers and rotors from the same 95 to 2001 Explorer. Well see what happens. I know I will need to build a driveshaft and put in a proportioning valve and master. I will also have some front brake parts to let go of if someone needs some. I overhauled the cylinders and they dont leak. One of the four has the bleeder valve head broke off but other than that its good. Shoes should be relined. I will be keeping my hubs as far as I know but when I take the drums off I would be willing to part with those. Project pics to come later.

[Don Coatney]

What gear ratio do these differentials have? Anything less than a 3.55/1 will not work well with a flathead 6.

[falconvan]

Im going to try the same swap this fall so Im looking forward to seeing how yours comes out. I've checked some specs; it looks like a lot of these Explorers had 3:73 gears.

[Plymouthy Adams]

the 3.73 is very common for that heavy of a vehicle and running automatic OD of roughly .70 giving you an effective 2.61 at cruise...however, the 3.73 rar gear however will only effective give you an 8 MPH increase in curise speed at the same rpm as the stock 3.9 going to the 3.55 will effectively give you approx 16 MPH crusie over stock and why most consider it the better choice and still be low enough enough not to put a strain on the flattie at start and long grades..

[Merle Coggins]

What's the gear ratio in your original diff/axle?

[DBRoadster]

"What gear ratio do these differentials have? Anything less than a 3.55/1 will not work well with a flathead 6."

Sorry, I'm new to the flathead 6's. I thought I read somewhere you wanted a higher gear ratio for these flathead 6's for lower RPM cruising? Does it just accelerate like a dog on anything lower numerically than 3.55:1? Wouldn't it give you a much higher top end speed also?

Edited April 12, 2012 by DBRoadster

[Plymouthy Adams]

your rear gear needs to be low enough to effectively get the hulk of steel rolling without straining your clutch..often if the ratio is too high the feather of the clutch and higher RPM to get the chassis moving is the result..the other extreme you already know,..if too low you are limited at top end and crusie but power off the line if great...finding middle ground is about the best thing you can in regard to ratio if you do not have access to an OD unit. Effectively, the 3.55 is still a good cruise (+16MPH over stock 3.9, 24 if you have a 4.1) and still not dog the enigne/clutch in stock form..going to the higher gear is not a bad chice today given the roads are not dirt and rutted as these cars normally say in thier day, the interstate high speed and long but less inclided grades make the lower ratios a thing of the past..the flattie develops its max torque at low rpm so this is also a plus when going to the higher gears..next biggest plus to modern rear gears is the brakes, self cnetering drum/shoe or disc is always a great safety device, can upkeep these easy with basic hand tools. The marriage of the rear e-brake cables to the original handbrake pull lever is not a hard job either giving the best of both worlds...

[DBRoadster]

That's what I was kind of thinking on the higher gear ratio. It seems like since these motors are pretty torquey and lower RPM'd, that a higher gear ratio would be perfect for it for good acceleration plus higher cruising speeds. Of course depending on the weight of the vehicle. I was thinking around the 3.21:1 range as a good medium.

[Plymouthy Adams]

It is quite possible to go that high..some have stated that feathering comes in at the 3.23 range..if you live in a relatively flat land area..you may be good to go..I did recently drive a 51 Plymouth with 3.9 rear gear and for kick and grims took it from a standing start up a very steep and I do mean steep drive in second gear smoothly..I have a stock 3.73 with my flattie..all other rear gears I have changed out go all the way down to 2.76 ration but these are being powered by V engines of various size and HP setups..no OD I go to the higher rar gears. rule of thumb in thinking if you will is the last of the rear wheel drive Chrysler 5th Aves with 318 came with stock 2.32 ratio gears..of course being automatics they have the advantage of torque multiplication on take off..it is all based on weight, ratio and torque..you can visit a number os sites and work the formulas for the best effective numbers match..but keep in mind not all paper racing will equate to smooth performance ont he road..error on the side of caution

[james curl]

On Tim's advice I installed a 90s Dakota 3.55:1 rear end in my 48 4 door P-15. I am running P205 R 75 15 tires which are close in diameter to the original bias ply tires that came on the car. Taking off in second gear is no problem what so ever. I sometimes take people around my little town, the old part and never shift out of high gear. You can pull without any problem in high gear below 15 mph by just giving the car more throttle, no bucking or snorting all the way up to highway speed. 70 mph with the 3.55:1 ratio rear end is running faster than the 80 percent of rated horsepower that is recommended for sustained driving. I drove mine on a 4800 mile trip where we ran 70 mph for miles on end in Nevada and as high as 75 mph on I-10 in west Texas. I did sustain some damage to the engine which developed after I got home. When I removed the oil pan I could see that the number 5 & 6 piston had extruded the wrist pin bushings. After pulling the head I discovered that the top ring on both 5 & 6 was broken which I concluded was caused by running 10 degrees initial advance thinking that all of the vacuum advance would not be used for lack of vacuum, I discovered that the engines still pulls 14 inches of vacuum at 70 mph which added to the initial and the mechanical advance is way too much advance, since then I only run 2 to 4 degrees initial advance and have not had any more problems.

[yourpc48]

Im shooting for the 3.55 but will settle for a 3.73. Right now my spedometer bounces a bit but from what I can tell with the ratio and tires I have now, 55mph shows as 70 on my spedo. I think that if I go with the 3.73 I will be using the 235-70 15 instead of the 225-70 15 tires I have now. I had some 235s on it when I first started driving it. I printed off a sheet that tells me the numbers for the tag on the rear so I can identify what Im getting. I do think that with a higher gear ratio like something in the 3.23 range that shorter tires would be in order. If leaving the tire and wheel close to stock sizes then yes I would probably not go any higher than the 3.55. My biggest problem right now is I drive it every day as an on-site computer technician and want to be able to go out on the highway without slowing traffic or burning up my engine. The disk brake situation is just a bonus. We all like to stop better.

[kkaiser001]

I am putting in a 91 Explorer rear axle right now in my Bus coupe. It has the 3.55 gear setup that wont be a problem since I plan on running a 318 Poly. I purchased new spring perches that are the same size as on the original axle so with a little mods and less grinding I will be able to use the same bottom plate with the shock setup. That's the plan anyway.

[Plymouthy Adams]

Poly 318 with auto you can easily go o a 2.9 series rear gear and still have plenty of power off the line..I remember well my poly 318 with automatic and 2.94 Posi..

[51wayfarer]

The '95 -'01 disc brake Explorers are available with 3.27, 3.55, 3.73 or 4.10s from the factory. In my experience, the 3.55 and 3.73 sets are most common.

[Don Coatney]

My point was do the math prior to installing any rear gear. I did so prior to installing a 3.55/1 rear gear. Works well for me. Install what ever gear set you want. But dont complain if it does not work well for you if you did not do the math first.

[yourpc48]

Thank you Don. Very good point. All that work and poor results would be bad. I want to change the rear because of the ratio not the newer brakes although that is a bonus.

I just arrived back from the wreckers and they had one disk brake rear end in the Explorer / Ranger / Mazdz PU type that I was looking for. Problem is that the one I found was a 4.10 so I didnt get it. I did however get rotors and calipers from the 96 explorer and a proportioning valve from a Jeep grand cherokee loredo. I will check back with them on another date to see if they get in a higher ratio in the disk brake type or I may have to go to drums again in the rear.

[yourpc48]

OK so I forgot to mention that the disk differentials 95-2001 have a tag that actually tells you the gear ratio. I found this out when I was taking pictures of the of the tag with my iPhone and wasnt ablt to make out the whole thing clearly. I pulled the tag off the rear so I could check it against the chart I brought with me and couldnt find the matching numbers to my chart. I then noticed that the tag actually said 4 10 88 xx x. This was a 4.10 gear ratio in an 8.8 rear end. I hated to leave it in the rig but thats basically the ratio my car has in it.

Here is a list of rigs and years that this style rear end should be in.

Ford Truck Explorer 1995 - 2001

Ford Truck Explorer Sport 2001 - 2002

Ford Truck Ranger 1998 - 2002

Mercury Mountaineer 1997 - 2001

So if you go out looking for one of these, looking at the tag should let you know exactly what you are getting without too much effort.

[Plymouthy Adams]

leave that one where it is unless you happen to have a OD unit to pop in the car..unless youjust have to have disc brakes..there are a number of other alternatives to consider..the Dodge and jeep setup will actually still allow for concentric mounting of your wheels..

[yourpc48]

leave that one where it is unless you happen to have a OD unit to pop in the car..unless youjust have to have disc brakes..there are a number of other alternatives to consider..the Dodge and jeep setup will actually still allow for concentric mounting of your wheels..

Yeah I plan on it. I am pretty sure I will be putting in an explorer rear because of the slightly narrower axle, the disks, and the sway bar. It looks like that way bar would work without too much effort but well see.

[51wayfarer]

The Ranger axle included in the group above is actually a bit narrower than the Explorer/Mountaineer, and has drum brakes and 28 spline axles (generally). Also, some Sport Tracs come with drum brakes. These links have probably been posted before in other threads, but everything that you need to know about Explorer/Mountaineer 8.8s can be found here, good primer before heading to the junkyard:

http://www.therangerstation.com/tech_library/Axles.html

http://www.therangerstation.com/tech_library/Explorer8_8.html

[BeBop138]

On my 52 Windsor with a modified 265 I am running 4.11`s with a T-5 and 235/75/15 tires---rpm`s at 65 are around 2500. A deep gear set like this isn`t the best choice for the small engines but I sure do like them for my application. The 3.55 for me did not pull as well as I wanted it to. My next choice was to go 3.73 but a buddy had the 4.11`s for free so I tried them---couldn`t be happier. With the Camero T-5 with the better gear spacing it did everything I was looking for. I did try the 3.25 set up first---had to downshift from OD to often...........my two cents........Lee

[Plymouthy Adams]

as a bit of advice to those who have trucks or maybe even want their car to have the pulling power of the trucks..and are wanting a T5 upgrade..go for the truck tranny from usually the larger series truck..these are wide ratio trannies and are the same gearing as the close ratio car series in 3rd, 4th and 5th but the 1st and 2nd gears are quite lower and give you that extra grunt most folks are looking for..

[yourpc48]

The Ranger axle included in the group above is actually a bit narrower than the Explorer/Mountaineer, and has drum brakes and 28 spline axles (generally). Also, some Sport Tracs come with drum brakes. These links have probably been posted before in other threads, but everything that you need to know about Explorer/Mountaineer 8.8s can be found here, good primer before heading to the junkyard:

http://www.therangerstation.com/tech_library/Axles.html

http://www.therangerstation.com/tech_library/Explorer8_8.html

I used the cross reference from NAPAs website to compare the rear rotor that was on the 95 explorer to other rigs that take the same rotor. The list I posted was from NAPA although they have been wrong before. I will check out the sites you listed. Thanks.