Axle bearing question

Beck · February 14, 2015, 01:37:44 PM

I am building a narrowed Ford 8.8 rear axle housing using aluminum. The center section is an IRS from a 2003 Mercury Mountaineer. The axle tubes are 2.5" 6061 aluminum schedule 40 pipe. The axles are 31 spline 1998 Explorer. I want to eliminate the C-clips. I would like to make aluminum 9" style axle ends, but I don't have any to measure for dimensions. The ID of the 8.8 axle bearing is 1.622, but these are the exposed roller style. The rollers run directly on the axle. I need the ID of the press on style bearing and seal to fit this axle size. The 9" housing dimension I looked up has a bearing ID of 1.537 and OD of 3.149. Is there a more standard size 9" bearing?

Worst case is I buy new axles which I should probably do anyway. Current plan is to cut and weld the axle. I could just buy short 9" axles. My main reason to install the C-clip eliminator is to have some leeway in axle length. With the C-clips the axle has to be an exact length.

A couple of companies make bolt on C-clip eliminators for the 8.8. I am machining all of the bearing surfaces anyway so I thought I would incorporate everything into the end of the axle tube. I would have to weld a larger end to the tube to machine to the 9" bearing size.

I thought I would post my problem here and someone may know of a simple solution.

This axle is going to be mounted rigid. No suspension. The outer tubes will be bolted to the frame and the center section will be bolted to cross members. The axle tubes will only be inserted into the center section about ½" but will be welded. Vehicle weight will be 1450 lb. Tire size is 34-18.00-15. It will be pulling as hard as possible. If I use the 9" style ends my plan is to weld on aluminum brackets to mount small GM metric calipers. Think it will survive?

You should see the look on wheel salesman's faces when I tell them I want 15x22 wheels.

jaybee · February 14, 2015, 02:30:35 PM

I assume this is for the pulling tractor?

I'd love to see some pics, both of the original unit and OF COURSE as you move through the project. I didn't realize these were 8.8" center sections...could they be used under a car?

enjenjo · February 14, 2015, 03:48:04 PM

I suggest you get a 9" axle, cut it to the right length, and turn down the end to fit in the 31 spline side gear, no splines, just the minor diameter. This would give you the bearing size, and spacing to have axles made. Then have new axles made to fit.

Second alternative, since you are considering welded axles, just use the 9" axles, and have Moser respline them for the length you need. If the axles are short, any 28 or 31 spline axle is big enough for 31 splines. Moser, last time I checked, got $80 plus shipping to respline axles.

Beck · February 14, 2015, 05:34:46 PM

Quote from: "enjenjo"
just use the 9" axles, and have Moser respline them for the length you need. If the axles are short, any 28 or 31 spline axle is big enough for 31 splines. Moser, last time I checked, got $80 plus shipping to respline axles.

Thanks enjenjo. You are my "Go to guy".
The Explorer axles are smaller between the bearing surface and the splines. I thought the 9" axles were also.
The axles will be 12 to 18" long.

Beck · February 14, 2015, 06:04:19 PM

Quote from: "jaybee"I assume this is for the pulling tractor?

I'd love to see some pics, both of the original unit and OF COURSE as you move through the project. I didn't realize these were 8.8" center sections...could they be used under a car?

Are you wanting photos of the rear axle build or the whole tractor build? This is going to be a long term project.

This will be a complete scratch built tractor. Some of the components used will be automotive. There was never an 8.8 used in a production tractor. Pulling tractor builders have used everything from 10 bolt GM axles to big semi axles depending on the size of the tractor. The 9" is a popular choice for my size tractor.

This rear axle would NOT hold up on a car. I am hoping to get by with it since I can solid mount the axle tubes AND the center carrier. Hopefully that will stop any breakage where the tubes and center section meet. On a vehicle with suspension the tubes would break from the center section. There is not enough tube insertion length into the housing. There would be room to machine that insertion depth deeper at a cost of reducing the housing strength.

kb426 · February 14, 2015, 06:28:32 PM

The reason axles are smaller diameter behind the splines is to instill the torsion bar effect. I've tried resplining 9" axles before in a gas dragster. They broke right at the end of the splines. We undercut them for a ways going away from the splines and they lasted alot longer.

enjenjo · February 14, 2015, 07:59:22 PM

I see no reason you can't add some ribs between the tubes and the center section since they will be welded together. It would make the joint much stronger.

wayne petty · February 15, 2015, 04:29:22 AM

if its a hard tail install. and i take it that you are using the stock mounting points..

and this is a crazy idea.. did you get the CV Shafts??? why not shorten those and mount conventional hub and bearing assemblies to mount the wheels and brakes on.. these hub and bearing assemblies would be bolted to the frame rails..

if you have a rigid enough frame. you might be able to mount shortened conventional axles right in the diff.. no tubes.. i like the idea of shortened center shafts in a CV axle.

heck.. why not blend the 2.. shove the straight axles into the inner CV joints. this would allow the frame to flex slightly.. mounting the axle outers in some kind of swivel bearing pillow block.. the axles are retained by the disc brakes and the snap rings that hold everything together.

you could also.. get double ended splined axles to do directly from the housing to conventional hub and bearing assemblies.

these are JUST Thoughts. .

Beck · February 16, 2015, 09:49:46 PM

Wayne,
I did consider all of your options before starting.

I am using the stock mounting points as in your photos. I removed the rubber bushing at the pinion and made a steel one. The cover mounts will also be solid.

A lot of the vehicles I was looking at had the hubs removed already, and others had bad bearings in them. That kind of scared me. Another concern of using the Explorer hubs was the top mount. It is like the pin of a ball joint. It doesn't provide much turning resistance. I like the hub design of the Lincoln LS better but the wheel bolt circle on those is only 4.25". The axles may be smaller also. The Lincoln LS hubs are aluminum the Explorer are steel.

After much consideration I decided there were more moving parts to rob power so I went with the conventional axle design. I even considered moving the center section forward a little and letting the CV joints angle forward. This would shorten the distance from the axle center line to the hitch hole.

I wasn't sure how much abuse the CV joints could take either.

Beck · February 16, 2015, 10:05:24 PM

I am progressing very slowly on the axle.

I have the axle tube machined on the ends for stock 8.8 bearings and seals.

I have made the solid sleeves to install in the center section and axle ends to put a 1.5" solid shaft through for alignment durring assembly.

I am using a posi center section out of a '98, non IRS, Explorer so it has C-clips. I noticed that the axle stub for the C-clip is what locates the spiders. IF you install 9" axles in the 8.8 rear, what locates the spider gears? 2 are on the cross shaft. The other 2 need something.

There is some debate if the posi carrier is going to work for me. There will be a load on the driveline. I want to be able to use seperate brakes on the rear wheels just like a larger tractor has. That will allow some steering when the front tires are off the ground. This is the common practice for the big tractor pullers. IF I have a posi will the posi lock the rear axles together enough to lug the motor if one brake is applied? If that is the case I just as well put in a lightweight spool or drop down to an open rear carrier.

I looked on the Strange sight for 8.8 axles. The price was $375. Is that each or a pair? Will they make axles to an exact custom length for the 8.8? They need to be exact to use the C-clip and still align with the brake caliper.

Unfortunately, I have more questions than answers.

kb426 · February 16, 2015, 10:13:09 PM

The Strange price should be per pair. They will make them whatever length you desire. A posi that is worn some will have some resistance but I don't have any exp. with what you're doing to know if it will kill the momentum. My thought is that with huge hp, you wouldn't care but with your small engine, it could be bad. Your rear wheels will be huge flywheels. Any braking has to be going in the wrong direction.

Beck · February 16, 2015, 10:48:01 PM

Anything beats running out of bounds. That is an automatic disqualification.

These little tractors can be a handful!

Here is a link to the last tractor I built. The photography is poor. This was powered by a 750 GSXR motorcycle motor. This was taken some time after I sold it. It had a solid rear axle. Notice how it is steered by leaning. Weight over a tire gives it more traction pushing the tractor the other direction.

The new one will be 400 lb heavier with much bigger tires and larger motor. It will turn less than half the rpm of the orange one. The engine flutter is the rev limiter in the video.

wayne petty · February 16, 2015, 11:22:00 PM

that puts a whole new spin on it.. was NOT what i expected at all..

wow...

i just don't see without a LOT of bracing that the reaction torque from what you are doing won't just break the sides of the case out if you weld tubes to it. but you have the vision in your mind. and the experience.

leaning out to assist steering.. creative. almost makes necessary to use a rear steering axle. like was used on chevy trucks a few years back..

cut and shorten the axle tubes but retain the steering. probably not legal.
hmm.. i wonder if one ran it toe in or if they ran it toe out what the self centering difference would be.

is the hitch mounting point adjustable. so you can control the front lifting and the rear lifting.. might be as easy as building it on a triangulated pivoting bar.. with a jack screw to change the height..

i can see a crazy idea that with the pull bar.. and the rear steering rear end.. one could fine tune the system so if the front of the tractor pulls one way.. the rear wheels shift the other way because of the change in draw bar angle on the pulling sled. probably not legal at all.

a half inch or so of height difference where the pull bar hooks to the sled could make a tremendous difference in traction

i even think that directional tires might be a help.. with single direction angles the dirt is thrown out from the middle so it does not pile up in front of the sled.

sorry to bring up more questions than answers..

enjenjo · February 16, 2015, 11:35:38 PM

Quotethe axle stub for the C-clip is what locates the spiders. IF you install 9" axles in the 8.8 rear, what locates the spider gears? 2 are on the cross shaft. The other 2 need something.

As long as the small gears have the pin through them, the side gears can't go any where. They fit in a recess, and the axle will hold them in place.

Beck · February 17, 2015, 10:03:45 AM

Quote from: "wayne petty"leaning out to assist steering.. creative. almost makes necessary to use a rear steering axle. like was used on chevy trucks a few years back..

is the hitch mounting point adjustable. so you can control the front lifting and the rear lifting.. might be as easy as building it on a triangulated pivoting bar.. with a jack screw to change the height..

Rear steering doesn't help much. The idea is to get the front of the tractor pointed in the direction you want to go. With rear steering the rear tires of the tractor are pointed down the track but the front is now trying to be the rear because it is still going the other way.

Maximum hitch height is listed in the rules. The higher the hitch the more down force on the rear axle. The axle center line to hitch hole is not in the rules. It also makes a difference. The longer the hitch the more leverage. This has to be combined with front weight to just get the front tires to float. If the front of the tractor comes up too high the hitch height goes down. All tractors in the class pull with the same chain of a specified length. We are required to run wheelie bars. If the front lifts to far force is placed on the bars and traction is reduced. With a small tractor you can lean forward and back to do some balancing.

Tractor pullers all want "moveable weight". That is weight that you can move from front to rear on the tractor to try to tune it to the track conditions. Some dirt has more traction so you want more weight on the front. Some is loose so you want to put the weight in the back. It is all a "best guess" before you make your pull.