Front end/Rear end Swap

[PeeWeeQ]

Ok, so, last winter, the driver's side rear axle broke on my M1009. I'm a bit do-it-yourself-er--I do most of my own work, within reason, on vehicles and stuff around the house.

I digress--I was very busy working on the railroad and I have very limited facilities in which to do repairs--like, my driveway. My single-stall garage houses all my tools, but, I don't have room to keep a vehicle in there, let alone have the space to work on one the size of my CUCV.

Any-who, a friend of mine on the RR said a friend of his had a front and rear end out of a 3/4 ton 1990 Chevy Suburban with 3:73 gears (the rear is a 14SF). I talked to the guy and he said that I could have them both for $175. I offered $150 and he took it.

So, now, I'm ready to pull the trigger on this and I have a few questions--

1. These aren't exactly stock equipment--for $150, I figured I could sell them later if they didn't work, but, how easy do they bolt up? Do I need to modify anything?

2. U-joints and drive shafts? Do I need anything different or do I need to modify anything? If so, what and how?

3. Brake lines? Same questions as above...

4. With a change in gears, I'm assuming my speedometer will be off significantly. Can I re-calibrate it, and if so, how? Does my tire size play any part in this? I'm going to have 31.5" tires...

5. Any procedural advice (what to do or not to do first or last)? Do I just go by the TM or is there a better resource?

6. Anything else I'm forgetting or not considering?

I'd like to chronicle this with pictures and a write-up so that someone else can have an all in one resource for the job, so, any advice to keep me on track and from totally botching this job would be greatly appreciated!!

Thanks in advance!

 

[Chaski]

1) They should bolt right up.
2) I think the front is identical. As for the rear I don't know for sure. Most 14 bolts have 1350 series u-joints
3) Unsure.
4) Yes, easily. Your speedo is driven off a plastic gear in your transfer case. You can count teeth on the one you have and calculate yourself what gear you need to make it correct again. Only catch is that there is two series of gear holders, one for the lower tooth count gears and one for the higher tooth count gears. Depending on what you have you may have to get the other style.
5) TM is good. Be sure to torque everything correctly and bleed the daylights out of the brakes.
6) I think you have everything. The parking brake should be identical, the only brake difference may be standard or metric banjo fittings on the front calipers.

 

[True Knight]

4. With a change in gears, I'm assuming my speedometer will be off significantly. Can I re-calibrate it, and if so, how? Does my tire size play any part in this? I'm going to have 31.5" tires...

After my tire size change to 37s I changed the gear in the transfer case to correct the speedo, however without tearing the transfer case apart to change the drive gear on the shaft I could only get the speedo so close. So I took the truck to a speedo shop (hard to find now days) and the guy hooked up a device and did a short test drive to see how far off the speedo was. He then made a small gear correction "box" that put the speedo within 2mph at 65mph. It screws onto the transfer case and the speedo cable screws onto the box.

 

[cucvrus]

My spin on the situation. I would change the broken axle shaft. It is about a 2 hour job tops. I broke 2 over the last year. Both were broken pulling fence post that were cemented into the ground along the road. More like guard rails then fence posts but it was a fence post. I was on the road in 4WD Lo and had great traction. It was alot easier to change then changing both axles and going thru the cobbling that you will end up with putting 3/4 ton rears in the M1009. Do as you wish. Good luck. I have a few pictures I will post of my axle shaft change. Total cost to do the job A 1 was about $100. that was changing both axle seals, e-brake cables, brake shoes,brake hardware and wheel cylinders. The axle shaft I had laying about and was worth $50 at the most.

 

[Recovry4x4]

The diameter of the rear axle is bigger. It takes a ubolt with that same radius. If at all possible, get the spring ubolt plates from the donor burb as you will need them.

 

[PeeWeeQ]

Good stuff so far--thanks guys.

cucvrus--I appreciate your input and several of my friend validate your view. They told me to just change out the axle--much easier. I do appreciate that, but, I guess I kind of wanted to prove I could do this, #1, but, I figure if I ever wand to run a bit bigger tires and do some serious towing and/or plowing (all very likely), the lower gears and a little heavier duty hardware couldn't hurt.

I should have clarified or expanded on my brake question a bit. What I'm wondering is, with the larger brakes (for sure on the rear), am I going to need a larger master cylinder, or is the one in there sufficient?

Thanks for suffering this fool--I'm kind of thinking this up as I go along.

And--Recovry4x4--That may have been the ONE smart thing I did: I saw how much bigger than stock the axle diameter was on the rear end right when I went to pick them up and asked if he still had the bolts and plates, do, he dug them out and gave them to me.

 

[NovacaineFix]

PeeWeeQ, I am so glad you brought up this topic as I am looking at the possibility of doing almost the same project, but for slightly different reasons.

My 1009, is pretty much factory stock, especially the suspension and axles. I have changed out the rear U-joints chasing a noise and the shocks but everything else is how I bought it.
Not trying to hi-jack your thread, but it is pretty much what I was going to post and maybe it can answer questions for both of us.

My idea was to put 4WD 1-ton axles under my 1009 for an pending body and suspension lift and tire and wheel change. I want to put 8-lug combat wheels on and go with a 36-37 inch tire, hence the suspension and body lift.
I felt that the stock 1009 axles would be the weak point if using a tire and wheel combination of that size and I didn't want to go the route of using spacers and a hub conversion for the 8-lug wheels.

But I also was looking at what "other" mods would have to be done, like PeeWeeQ's idea, the u-joints, different yokes/adapters?, did the spring perches need to be re-located on the rear axle, are the steering components going to be the same (pitman arm).
I even thought if I could reduce the weight and go with a coil over conversion and ditch the leafs, would that work. But I know that would be more $$.
My biggest worry that if everything is do-able and very workable, is the stock 6.2 going to live up to pushing all this new(er) metal up the hills.

 

[cucvrus]

cucvrus--I appreciate your input and several of my friend validate your view. They told me to just change out the axle--much easier. I do appreciate that, but, I guess I kind of wanted to prove I could do this, #1, but, I figure if I ever wand to run a bit bigger tires and do some serious towing and/or plowing (all very likely), the lower gears and a little heavier duty hardware couldn't hurt.

Hey in the amount of time you are asking and contemplating this issue you could have changed the axle shaft and rebuilt the rear brake system. . No do as you wish. i do not have bigger tires I like to flex and stuff my suspension to much for that.I am a Mad Man on the trails and flex ramp. I need to replace all the spring bushings one of these days. I see Energy Suspension parts in the near future for Terminus M1009.

 

[PeeWeeQ]

Alright...I'm trying to get all my ducks in a row before I start, so, TWO questions remain:

1. The question about the brakes...

2. The rear drive shaft--It looks like the front is that same...How do I deal with this thing? Obviously, one end is going to bolt up to the t-case just fine, since, that's where it came from. But, what about the end with the new rear end? Do I need a new drive shaft all together? Should I have taken the one from the old 'burban and modified it (I should say HAVE it modified)? Difference in length????

I suppose it might be wisest to just get everything mounted up and take it to a shop where they have the experience to handle it...Any idea what they might have to do and how much it might cost?

Thanks guys!!

 

[patracy]

Rear drive shaft, you're probably going to have to run a bastard u-joint. I did this years back in a suburban I have. It's basically the same as the half ton yoke on the driveshaft then on the other two caps, larger/wider for the 3/4 ton yoke of the pinion. $20 fix really.

 

[PeeWeeQ]

Thanks! How do I go about that--piece together one u-joint from using the caps from 2 different u-joints? Any ideas about the drive-shaft length?

 

[patracy]

You don't, you buy the "bastard joint" as an assembly. It's been decades since I used one, I've long since forgotten the number. You're going to need to go to a NAPA or somewhere that will look up the u-joint specs, then find the adapter joint you need.

 

[cucvrus]

The rear drive shaft will be shorter then when the 10 bolt rear axle was in place. You need to get the angle of the driveline correct also. You could create some nasty vibrations and breakage on the rear with that hard angle.

 

[patracy]

He's going to run the 9.5" semi floater rear end. (At least that's what I assume by the 14SF he mentioned)

 

[cucvrus]

OK I was thinking the 14 bolt was the same size center housing size regardless FF or SF. Sorry. I am out of tune on this. I will retreat to my home.

 

[patracy]

OK I was thinking the 14 bolt was the same size center housing size regardless FF or SF. Sorry. I am out of tune on this. I will retreat to my home.

Good bit of difference between the 14SF and FF rears. Especially the housing center and how the pinion installs. No worries. GM made it difficult when they're both "14 bolts".

 

[Skinny]

Not that a SF 14 bolt is a huge upgrade but it's better than a 10 bolt by far. The front end you won't gain really anything other than a few extra lug nuts. The gearing will probably help and also let you run a slightly larger tire. I say go for it. It's just some time and money, the swap you are proposing isn't exactly rocket science. The trucks are very close to plug and play.

 

[PeeWeeQ]

OK, Sooo, with the 14 bolt SF, I WON'T need a shorter drive-shaft? Just the "bastard u-joint"? This is the front and rear ends I have, by the way, just for your verification....

 

[Recovry4x4]

Front shaft will require nothing to bolt on, it will be perfect. The rear you will need that combination u-joint and a close look at the driveshaft while in place. The pinion on the 9.5" 14 bolt is just a little bit longer than the 10 bolt. If anything, you may need to shorten the shaft just a bit. Is there any kind of lift going on at the same time?

 

[PeeWeeQ]

Nope, no lift right now. I'm going to have 31 x 10.50 tires, so, I don't see a need at the moment. If I go with 33s-35s in the next year or two, I'll consider it then.