3/4 ton rear axle swap

[Jeff Balazs]

Hi Guys;

I am trying to determine what the optimum rear axle swap would be for my truck. I have a 52 3/4 ton with 5-5" wheels (which I want to retain) and a 230 fluid drive with a 4 speed synchromesh transmission.

Merle has suggested that a 2000 Grand Cherokee rear axle might make a good candidate as it would have disc brakes with a 5-5" wheel pattern. It appears that these are commonly available with 3.55 or 3.73 ratios.

My thinking is that perhaps a slightly higher ratio like 3.23 or even 3.07 could be a better solution for today's roads.

I have been surfing the web for more info on axle swaps but I just have not found the right info to help me make this decision. Your feedback and input would be appreciated.

Thanks, Jeff

[B1B Keven]

Some Dodge 1/2 ton 4x4's used the 5 on 5 pattern. No rear discs though.

3:23 or 3:55 would be about perfect. (The 2:76's I'm running are too tall).

[Jeff Balazs]

Thanks Keven for your input.

I am just guessing here but I would think 3.23 is probably going to be as close to optimum as I could hope for.

I would not mind rear drums....just want 5 x 5 pattern so I don't have to use wheel adapters. I am going to contact AAJ Brakes and see if they do a front disc conversion that takes 5 x 5 pattern rotors. It is worth a try.

I have been trying to find a website with comprehensive axle spec's like hub to hub width, wheel patterns, ratios etc.....but so far I am just finding bit's and pieces of the picture. It is really hard to know what to look for when you don't have a clear idea of what is out there. And I suppose it doesn't help that I have never really done this before. Fortunately I have a great fabricator....I just need to find him the right component.

Jeff

[B1B Keven]

Maybe this will help?

http://www.hemmings.com/mus/stories/2007/01/01/hmn_feature21.html

[Jeff Balazs]

Keven;

Yes....sort of.....according to this it tells me that the Chrysler 8 1/4" axle was not offered with a 5 x 5 wheel pattern. Too bad as they appear to be fairly affordable.

Jeff

[B1B Keven]

Hmmm. I could have sworn some Dodge had that axle.

Here's a possible doaner:

1999-2011 Jeep Grand Cherokee

[Jeff Balazs]

Keven;

That is the one Merle mentioned. And it may certainly be the best choice.

There is a 3.07 ratio model......then it looks like it jumps to 3.55.

I do know the 3.55 would be an improvement over my 4.10 but is it optimum? What I am really uncertain of is if the 3.07 would be a better selection? or would it be too tall a ratio for the truck?

Jeff

[B1B Keven]

3:07's would probably be OK. Just don't expect a lot of acceleration.

Highway speeds will be good.

[Merle Coggins]

Knowing how my truck runs with 3.73 gears, I'd be leary about going below 3.55 if you have any hills in your area.

When I was with Tim yesterday he was telling me about the axle that was put into his truck. He wasn't positive, but thinks it may have been from a Ford Ranger. Did they have 5" pattern?

Merle

[Jeff Balazs]

Merle;

Oh yes we have hills here and not too far off ... mountains.

I doubt I will be pulling any big hills with a load in it. But there are some grades on our highways and freeways that need to be taken into consideration. The Sepulveda pass and the Camarillo grade on the 101 north out of the LA basin comes to mind as a couple that I would definitely be using from time to time.

Of course good brakes are important on both of these. I would ask Hank if he has been on either of these with his truck....but I bet I already know the answer.

If I end up going with a Grand Cherokee rear axle and do a front disc conversion then I was figuring on using a master cylinder out of one of these as well. Does that sound right? I want to get all of this taken care off while I have the cab off. It will be much easier to run all the lines then. I am not planning on any other significant mods to the truck but I really want to get these right.

Thanks again, Jeff

[Dave72dt]

Ideally, you would want a MC and proportioning valve out of something the had approximately the same total weight and front to rear weight bias as the truck but because that makes things real technical and impractical, use the one from the donor.

[Jeff Balazs]

Hi Dave;

Thanks that is what I thought.

Btw......I am more than half way through taking it all down to bare metal.

The good news is the cab is in very good shape. The rear fenders ....one of the fronts and one of the doors are not as nice as I originally thought. No holes....not much rust.... but a fair amount of bondo was lurking under the primer. I guess I am going to get a chance to develop my hammer and dolly skills. Oh Boy! Fortunately I don't really want it to look new so some of the dents may just stay as a nod to it's past life.

Jeff

[Scruffy49]

73-87 2wd Chevy 1/2 ton pickups. 5 on 5 with front discs and rear drums stock, rear disc kits readily available. And dirt cheap. Unlike late model Jeep stuff (at least around here). And the gear ratios are all over the place, my father in law's 85 4.3L/TH350 has a 2 something ratio. Decent fuel economy, great highway manners, but takes off from the line like an anemic turtle.

Rangers mostly had 5 on 4.5, same as PH 1/2 tons. Maybe the post-97s had the larger pattern, not sure since mine are a 92 and a 94. 92 is a parts junker for the 49 Dodge and the other Ranger.

[Jeff Balazs]

Scruffy;

I did look at those but it seemed like they were too wide. Maybe I am wrong?

Also if I am not mistaken this would require the drive shaft to be modified...again I could be wrong?

Jeff

[Dave72dt]

Track width for a '83 C10 rear axle is 62.5" . I think they use a trailing arm and coil spring type suspension.

[Jeff Balazs]

Update:

We went ahead and bought a 2002 Grand Cherokee 3.55 Dana 35 rear axle with 5 x5' disc's. It should be here by the end of the week. I will let you know how all this goes.

Getting excited now..... My buddy Jon has been looking at the front brake situation and thinks it should be fairly easy to fabricate brackets to mount 5 x 5" disc's up front. That would be very cool.

Jeff

[Scruffy49]

The 10 bolts in the refrigerator box C10s were on leaf springs, trailing arm and coil went away in 72. You'd have had to get the 10 bolt narrowed.

When I swap a later rear into mine I'll need a new drive shaft made, mine has the funky u-joints. With any luck, Ranger rear axle/brakes, Ranger 5 speed, shortened Ranger driveshaft (114"wb donor truck).

Best bet is a C4 Corvette IRS, only have to add 1/32" shim plates to each side of the frame to get the right width. But, you'd drop the truck by a lot of altitude...

[Jeff Balazs]

Scruffy;

Yes that is what I thought.

My Grand Cherokee replacement axle will be here tomorrow. Should be pretty straightforward.

I called AAJ Brakes today and they are going to send me info on their front disc set up that supposedly will take 5-5" bolt pattern rotors. The owner told me he also does 8 bolt rotor kits for the larger trucks. This will be very cool if it all pans out.

Jeff

[Jeff Balazs]

Progress on my axle swap is moving forward.

Fitted new rotors and calipers to check wheel clearance. Looks like a 3/8" thick spacer plate between the rotor and the wheel will give me the clearance I need to run the original wheels. These disc's are 12 " diameter so it is a tight fit with the stock 15"wheels. Need to find a set of proper caliper mounting bolts....no luck yet on these.

The Grand Cherokee Dana 35 rear axle is about 1/2" wider than the stock axle so no real issue there. Should wind up with about a 1 1/4" wider track in rear. The Jeep axle accepts the original U-joint perfectly. This axle has a shorter distance between the center of the axles and the u-joint yoke by about an inch as compared with the stock axle. Looks like the stock drive shaft will reach fine just as it is.

We have just about finished straightening the frame. All that is left now are minor adjustments and cosmetics. Whew! I really was not sure we could do this ourselves. Hat's off to my buddy Jon who is a real metal working ace...and the hydraulic rams..etc that made this so much easier than I ever expected. With any luck the frame and axle swap will get done in the next week or so.

Jeff

[HanksB3B]

Glad to hear it! Hopefully it's all fun from here on.

Hank

[Jeff Balazs]

Hey Hank;

That would be nice.

The whole bent frame thing really threw me for a loop. Wasn't prepared for that kind of effort. And Jon has been busy with his own work....so. But we are finally down to the last few "adjustments". Once we are done with that and some cosmetic repairs it should start moving forward a lot quicker.

In the meantime I have the body about 80% down to bare metal. Still need to get some blasting done then we will see what this thing is going to look like in Tan. I am going to leave some of the dents, dings and creases as testimony to it's being a 60 year old truck. I know that is not your style but to my eye a truck this old has earned all it's battle scars and they should show. I will be very happy if when I am done this truck looks like it came off an old cattle ranch.

Jeff

[HanksB3B]

"Well take a look over yonder boy, that's one sweet old Pick Up now ain't it!

Hank

[Jeff Balazs]

Now there you go.....The Duke was all right!!!

Got to talk with him once aboard the Wild Goose back around '74. Great Guy....they don't make um like that anymore.

It's funny although he made a million westerns my favorite movie of his is Blood Alley.

Jeff

[Jeff Balazs]

The Grand Cherokee axle is in......Yeah!!!!! And the Drive shaft worked out just as it was....Yipppeeee. Oh Boy am I getting excited.....12" rear discs...:D:D

I ordered Charlies conversion kit for the front so once this is all in and plumbed up it should stop really well.

This is the only significant modification I am making to the truck. I started off by replacing the entire original braking system but got to thinking that traffic in the LA Basin just does not allow for marginal brakes so...I will have a fresh set of wheel cylinders, a unopened original type master cylinder and new brake shoes etc.....If any one is interested I will make you a deal or we can do a trade?

Jeff

[HanksB3B]

Way to go Jeff! Would like to see some pictures (of course).

Hank