8.8 Axle Swap Into A 90 Comanche

[Biotex]

Personally, I think the Ford 8.8 axle swap into a Comanche makes a lot of sense for many reasons.

Reported to be 20% stronger than a D44.

Readily available, and fairly inexpensive.

Good aftermarket support.

Comes with factory disk brakes.

Fairly easy swap that most people can do themselves.

Same bolt pattern.

 

There are a few down sides to the swap. The axle is about 1.25" narrower then the Jeep axle.  That works out to about 5/8" on each side. To make up for this, most people just run a 1" spacer. Quality spacers are not cheap, so that is why I consider it a down side. The axles are held in with "C" clips, so that is generally considered a downside as well. The 8.8 uses a flange style yoke, so that will need to be addressed. More money possibly, so another down side. Finally, the width of the 8.8 and the 5 lug bolt pattern severely limits your choices for a matching front axle if you ever decide to upgrade the D30.

 

1991-1994 versions had 10-Inch drum brakes but the 1995 and newer models come with disc brakes. The 95 or later Ford Explorer makes a good donor vehicle because they had disc brakes and 31 spline shafts. You will also find that many were limited slip.  They came in all the common gear ratios, 3.55, 3.73, 4.10 for example, so you can search around for the ratio that suits your tire size. I paid $300 for the axle used in this write up. Not a great deal, but not a rip off either.

 

The tubes on the 8.8 axle are 3 1/4" dia. so you will want to source some brackets that will match up to that tube size. I purchased the ones from Barnes 4WD, and that is also where I purchase the rest of the parts pictured for the swap. When I removed the axle from the Explorer, I kept all the U-bolts and nuts just in case.  I know you are supposed to use new U-bolts and nuts, but I liked how the OEM ones are flat instead of the round ones you always see.

I'm going to re-use them.

 

 

One nice thing about aftermarket spring perches is that they are drilled with three different mounting points so you can easily change your wheel base. This can be handy for fine tuning your drive shaft also.

 

I'm going to stay spring under for my build, but pretty much everything will be the same as far as this write up is concerned.  Due to the larger tube diameter (3.25") compared with the D35 (2.5"), and the differences between the height of the spring perches, you will losing about an inch of lift. For SOA, you will gain an inch or so...

 

If you are careful when you remove the old perches, you can save some money by just re-using them in the new location. I haven't made up my mind yet if I'm going to re-use these.

Here you can see the OEM perches I cut off the tubes:

 

 

Here is the complete axle after cutting off the perches and shock tabs.

It is worth mentioning also, that there are two different suspension systems used on the donor vehicles. Leaf and coil springs. I chose the leaf spring setup when I picked up the axle at the salvage yard because it looked easier to remove all the old brackets off of. Thus mine is not the beefier 31 spline shafts. Still stronger than a D44, so no worries there.

 

 

The 8.8 has a speed sensor that fits into an opening on the housing. You could leave it in place, but I elected to take it off, and make a new cover for the hole.

 

 

Here is the new cover I made. I'll put a bit of RTV on for a gasket, and bolt it in place.

 

 

That is it for now, since this is a work in progress, I will add more as the time comes.

[Biotex]

As I mentioned above, the 8.8 uses a pinion flange instead of a pinion yoke. The pinion flange uses 12mm x 1.75 thread bolts. They are 12-point bolts Ford P/N N800594-S100.  I saved the old ones when I took out the rear end just in case.

You can purchase an adapter called a flange yoke that connect this 8.8 flange to the larger 1330-style U-joints or the smaller 1310-style U-joints. I'm not sure which direction I am going to go with this swap yet. I will address that part later.

Here is a shot of the OEM flange:

 

 

Here is what the adapter looks like:

 

 

They can be had for around $65.

 

 

Another thing that will need to be worked out, are the shock mounts. Since my truck is lifted 4 or more inches in the front, and approximately 3" at the rear with the military wrapped springs already installed,  I purchased a pair of these shock mounting brackets (also from Barnes 4wd).

 

 

They are for a smaller diameter axle tube, but easy enough to grind them a bit larger. I figure with the lift, I will still have plenty of travel , but won't know for sure until I get to that point. Since I am writing this as I go, there will be some things that need to be worked out on the fly so to speak. Shock mounts fall in that category, because everybody's lift is not the same. On an MJ with no lift, I'm not sure you would want to use this type of a shock mounting method. Perhaps something with more angle such as /   \  would be better suited. More vertical, and not enough travel. Too angled, and you lose effectiveness.

[Biotex]

The easiest way I find to remove the rear axle, is to put both rear wheels off the ground by putting jack stands under the frame just forward of the front leaf spring mounting brackets.

Remove the drive shaft at the pinion, leaving it in the transfer case so you don't lose oil if you still have a slip yoke.

Remove the brake line where it connects to the rubber hose, and take the rubber hose off of the frame mount so it will come out with the axle

Remove the lower shock mounting bolts.

Remove the brake proportioning/ leveling rod where it connects to the ball stud at the diff. cover.

Remove the vent line at the axle tube, driver side.

Remove the four nuts holding the u-bolts on, and remove the spring plate and stiffeners.

 

The axle should be just resting on the springs, with nothing connected.

 

Put a floor jack under the leafs  on either side. By taking some of the weight off of the springs, the rear mounting bolt will come out easier because it is not having to hold up the weight of the axle. You can remove the bolt at the rear shackles, and then lower the jack so the axle weight is now on the tire. The spring will rest on the ground. Repeat for the other side.

 

 

You may or may not have to remove the tires and rims from each side so you can roll or lift the axle off the springs, and out to the rear.

Set the 8.8 axle in place of the one you just removed.

 

 

Put your new, or used spring perches onto the springs, and set the new axle onto them as pictured. Here I'm using the old ones I cut off from the axle tubes.

They won't be tacked into place until later when we set our pinion angle.

 

Take your floor jack and lift each side one at a time, and reinsert your shackle bolts as pictured.

 

 

Also install your new spring plates & U-bolts. Just barely snug because we need to be able to move the axle left or right, and be able to rotate it for the pinion angle.

The left and right adjustment is so the axle is centered evenly for proper track. I measured with a straight edge from the frame down to the tube, then over to the flange at the end of the tubes behind the backing plate. The idea here is to get the axle perfectly centered left to right with the springs hanging straight down with no binding. It takes a while if you are by yourself, but much easier with help. There are a lot of places you could measure from, so whatever suits you.

 

Once the left to right part is finished, I tighten up the U-bolts a bit more so the axle won't shift around, but not so tight you can't rotate it. I start with the axle pinion angle lower than is need to be, because it is easier to raise it with a jack, than to lower it.

 

So now I set the weight of the truck on the tires so I can get ride height. I use a digital angle finder to measure the down angle that the transfer case is at. Mine was approximately 6°.

The 8.8 has a flange for a yoke, so real easy to put the angle finder on it and raise the jack until the flange is 4° or 5° up. You want the pinion angle to be a couple of degrees lower than it needs to be, because it will raise when torque is applied to the wheels. So when you are going down the road, it will end up at 6° up, and match the angle the transfer case is at.

The idea here is that the rear pinion shaft is parallel to the output shaft of the transfer case while forward torque is applied to the driveshaft.

 

Once the pinion angle is set, you can tack the perches in place. You can now tack your shock mounting brackets in place.

 

 

With the wheel at full droop, I set the shock mounts so there was 3.5" of down travel left, and the rest was up travel. I had measured my shocks to have 7" of total travel, so at full stuff, I will probably bottom out. I didn't want to rotate the shock mounts any further down, or the sides of the shocks would hit the axle tube. Also a better chance of snagging a rock. I believe a couple of inches shorter shocks would be ideal, but these will work for now. I can fine tune them later.

 

Once the shock mounts and perches are tacked in place. you can remove the spring plates again, and rotate the axle so you don't have to weld upside down.

 

My measurements show that the drive shaft will have to be shortened one inch. A solution is to use spring perches like picture in the first post, so you can stretch the wheel base 1" by using the rearmost set of holes.

 

This measurement is taking into account for the flange adapter you will need. I have one that came out of a Rubicon Jeep, but it is not for the 1310 u-joints. I'm going to either shorten the drive shaft and purchase a new adapter for 1310's, or buy a new drive shaft and a slip yoke eliminator set for the beefier 1330 U-joints.

 

More to come...

[Bornindesert]

Subscribed - what were you thinking of doing for shock mounts?

[Biotex]

Subscribed - what were you thinking of doing for shock mounts?

 

Please see above where I added some more to the document. This is very much a learn as I go project, so I don't necessarily have all the details worked out yet. There are a lot of different ways of doing things, so I tend to tackle them one at a time as they arise, but I have a decent idea in a broad sense of what is involved. Shock mounting is going to be different for everyone, since it depends on how much travel they need.

In my case, I have about 3" of extra lift in the rear over stock. I already installed longer shocks, so moving the lower mounting point up on to the axle will compress the shock a couple of inches compared with the oem mounting spot on the lower spring plate. Once the axle is in place, I can figure out the best compromise between clearance and travel.

I will add these details to the write up at a later date when I can get more specific with measurements and such. I'll also take photos of course...

Thanks for asking.

[Zebvance]

I'm doing the exact Same swap right now. I intrested to see how you do your brake lines, where you mount the shock mounts and how much clearance the perches have from the brake caliper. That is if you are soa like I am.

[Biotex]

I'm doing the exact Same swap right now. I intrested to see how you do your brake lines, where you mount the shock mounts and how much clearance the perches have from the brake caliper. That is if you are soa like I am.

SUA, because I have some lift already built into the military wrapped springs. I'd be at or around 9" lift if I went SOA.

[92tanMJ]

 

I'm doing the exact Same swap right now. I intrested to see how you do your brake lines, where you mount the shock mounts and how much clearance the perches have from the brake caliper. That is if you are soa like I am.

SUA, because I have some lift already built into the military wrapped springs. I'd be at or around 9" lift if I went SOA.

 

Yolo!!

[Zebvance]

Yea I'm at 9 inches of lift in the rear right now.

[Biotex]

When I pulled the 8.8 axle, I got the complete brake lines to go with it. The female fitting on the end of the rubber hose is the same size as the Comanche male brake line fitting, so just screw them together no problems. If you have some lift, you will want a longer hose, or do like I did and let it all be loose. I will come back and secure things later if needed. More on that later.

[Biotex]

The E-brake cables that came already installed on the new 8.8 actually will bolt right up in place of the MJ ones. The only problem I see is the short side (driver side) will have to be swapped out for another longer one like the passenger side. DORMAN C660004 is the part number for the right rear cable. Length is around 78".  A little longer than is needed, but certainly enough to cover any size lift.  They are under $15, and an easy swap.

 

 Pictures to come.

[Bounty Hunter]

Being a c-clip axle isn't a downside, have you seen an 8.8 fail due to c-clips? And I'd question being 20% stronger than a d44.

 

Don't forget they commonly spin the axletubes inside the diff housing under a load. This is usually solved by welding the tubes to the housing. I used 55% nickel rods when I welded mine.

[Biotex]

Being a c-clip axle isn't a downside, have you seen an 8.8 fail due to c-clips? And I'd question being 20% stronger than a d44.

 

Don't forget they commonly spin the axletubes inside the diff housing under a load. This is usually solved by welding the tubes to the housing. I used 55% nickel rods when I welded mine.

Not a downside due to strength. Just because it is not as easy to swap in a new axle on the trail.

 

As for the tubes spinning, yes they can. I added a weld to mine on the bottom, hard to reach part. I can easily stich in the rest later. I don't have the confidence in my welding skills, so will take it to a friends house when it is drivable. He has nickel rod also...

 

As for the 20%, don't know. I read that on 3 different sites when researching for this swap. Maybe it is just bad info perpetuating itself, but I have no doubt it is stronger than a D44, but how much, IDK.

[Biotex]

I re-welded on the old spring perches. In hindsight, I wish I had used the aftermarket ones that allow you to move the axle forward or rearward up to 1". By stretching the wheelbase that 1", the OEM driveshaft would be the correct length. Those aftermarket perches pictured above in post # 1, also reduce axle wrap. Moving the axle back 1" may or may not cause tire clearance issues. It wouldn't in my case, so I wish I had gone that route.

 

If you decide to do this swap, and you are going with a new rear driveshaft, it would be more cost effective to have the shop install 1330 joints. They can custom make the shaft with the yoke adapter and beefier joints on both ends already installed. I use Tatton's driveshafts. Curtis (CJ) is the owner. His shafts have the same warranty Tom Woods has, for a lot less money.

 

He also sells slip yoke eliminators if you really want to do it right.

[Biotex]

Ran into my first snag today when my Currie companion flange adapter arrived.

 

Currie (bought from quadratec) sells an adapter for mating a 1330 U-joint to an 8.8 flange. Trouble is, the bolt pattern does not match up. My axle came out of a Ford Explorer which is the truck line, so it needs a 1330 style adapter with a 3" hole spacing. The currie adapter is sold for the car line axles.

 

Since Tatton's drive shaft is making me a new shaft, I gave them a call and an extra $45 to add the correct adapter on to the end of the new shaft. This is what I should have done in the beginning since now I will be getting the beefier 1330 joints on the pinion end of my new shaft.

 

So total cost is now $150 for the shaft with joints installed, and balanced. $45 for the companion adapter, and $35 shipping charge.

[xjustinx]

Just an FYI your axle is a 31 spline axle. 

[Biotex]

Really. How can you tell? I thought only 95 + were 31 splines, and I'm thinking I pulled a 94 or late 93 from the salvage yard. Could be wrong, as it was a couple years ago.

Just an FYI your axle is a 31 spline axle. 

[HOrnbrod]

The E-brake cables that came already installed on the new 8.8 actually will bolt right up in place of the MJ ones. The only problem I see is the short side (driver side) will have to be swapped out for another longer one like the passenger side. DORMAN C660004 is the part number for the right rear cable. Length is around 78".  A little longer than is needed, but certainly enough to cover any size lift.  They are under $15, and an easy swap.

 

 Pictures to come.

 

I not sure you can do this with the Ford axle, but why can't you swap the backing plates and mount the calipers facing forward? Then the ebrake cables would be plenty long enough and easier to run too. That's how I set up the Explorer disks on my D44.

[Blue88Comanche]

what is the amp output of the welder you are using?

[xjustinx]

 

Really. How can you tell? I thought only 95 + were 31 splines, and I'm thinking I pulled a 94 or late 93 from the salvage yard. Could be wrong, as it was a couple years ago.

Just an FYI your axle is a 31 spline axle. 

Cause all the explorers had 31 spline axles and the 94 and earlier were drum brake axles. The 8.8 out of the rangers had 28 spline axles, thats prob what you were thinking of. 

[Biotex]

what is the amp output of the welder you are using?

 

Millermatic 251

 

250 A at 28 VDC,

40% Duty Cycle

 

200 A at 28 VDC,

60% Duty Cycle

 

Why do you ask?

[Blue88Comanche]

what is the amp output of the welder you are using?

 

Millermatic 251

 

250 A at 28 VDC,

40% Duty Cycle

 

200 A at 28 VDC,

60% Duty Cycle

 

Why do you ask?

Just wondering, I have been looking into getting a better welding machine than my 90 amp Harbor freight. It's good for small things, I already killed one while working on a small project but, thankfully the warranty replacement was simple.

[Biotex]

As a follow up, I'd like to add that now after driving the truck around a bit, I am going to do the 95/96 XJ brake and master cylinder upgrade. The stock MJ unit doesn't push enough fluid for the more massive rear calipers. I could "get by" with it as is, but would rather perform the upgrade so I can take full advantage of rear disc brakes. I still have a working load sensing valve, so the plan is to leave it in place and use it to fine tune the pressure to the rears. After the XJ upgrade, I will test drive again and re-visit this decision.

[92tanMJ]

As a follow up, I'd like to add that now after driving the truck around a bit, I am going to do the 95/96 XJ brake and master cylinder upgrade. The stock MJ unit doesn't push enough fluid for the more massive rear calipers. I could "get by" with it as is, but would rather perform the upgrade so I can take full advantage of rear disc brakes. I still have a working load sensing valve, so the plan is to leave it in place and use it to fine tune the pressure to the rears. After the XJ upgrade, I will test drive again and re-visit this decision.

 

Wouldnt it be easier to ditch the valve now when youre doing the ungrade, then later when you'll have to cap it some way?

[Biotex]

 

As a follow up, I'd like to add that now after driving the truck around a bit, I am going to do the 95/96 XJ brake and master cylinder upgrade. The stock MJ unit doesn't push enough fluid for the more massive rear calipers. I could "get by" with it as is, but would rather perform the upgrade so I can take full advantage of rear disc brakes. I still have a working load sensing valve, so the plan is to leave it in place and use it to fine tune the pressure to the rears. After the XJ upgrade, I will test drive again and re-visit this decision.

 

Wouldnt it be easier to ditch the valve now when youre doing the ungrade, then later when you'll have to cap it some way?

 

I'm trying to do this upgrade in stages so I can evaluate by putting some miles on the truck between the tweaks. This way I can report back more accurately.

I knew from reading many others accounts on other threads that the stock M.C. doesn't push enough fluid for rear disc brakes, but I wanted to see for myself just how good/bad it was.

Now I can honestly say that without upgrading the booster, and with the load sense valve still in place, I couldn't lock up the rear brakes. I tried putting the sense valve in several different positions until the pedal felt the firmest.  I felt like the brakes were no better than with rear drums. Now by changing only the M.C. and Booster, I will test and report again.

Inevitably, I will end up removing the sensing valve I'm sure. I will also need to evaluate the proportioning valve.