A1 Cab -> A0 Chassis Swap

[yertnamreg]

I've been lurking for a bit but I'm excited to make my first post. Hi, I'm yertnamreg and I'm down in Houston. I took the plunge last week and bought one of the 1085s out of Bragg! It's definitely a little rough around the edges, but she seems to have good bones.

I got interested in getting one after working on a friends and seeing how much potential these trucks have. Ultimately I'd like to build the truck into a camper/expedition vehicle.

I decided to take a risk on this truck because I found something interesting on another auction site... A1 cabs that were basically brand new. I ended up purchasing one of these with the intent of swapping it onto my A0 chassis. Compared to the cost of buying individual pieces like new door latches and a turret cover, this was a much cheaper option and provides a few upgrades like insulation.

At this point you're probably worried about electrical...seems to be a common concern with folks on here. I do expect there to be some differences, but I'm confident the cab can be adapted to work with the systems on the A0 chassis. I've read up on the A1 TM situation, so I know there isn't much information out there. I'm an electrical engineer professionally, so I'm hoping I can reverse engineer something. If you have any insight you can share it would be greatly appreciated.

I'll post updates on the swap here. Excited for the truck and cab to get here later this week!

 

[NDT]

Welcome, truck looks good and seems to run fine. Looks like Uncle tried and gave up fixing the brakes. You need some tires, member simp5782 will be heading to Houston soon with a load of tires for me, contact him for a great deal on some MV/Ts. I'm down in League City if you get stuck fixing the brakes, I have suffered through a lot of that and can help. Most of us are not very excited about the A1 electrical system.

 

[FMTV Truck Sales]

We have swapped many A0-A1 cabs...there are a number of differences to be aware of:

- Most likely there will be a difference in air fittings where they enter cab on bottom.
- Throttle pedal mounting will need to be modified/fabricated.
- The wire harness on the A1 will not fit the A0 so you will need to keep your old harness and re-mount in new cab (along with power distribution panel).
- Instrument panel will have to be swapped with harnesses
- A few of the "firewall"-mounted components will also have to be swapped
- Rear cab mount/latch and bracket will have to be swapped with original (should be direct bolt-on replacement)


That's all that comes to mind - good luck and feel free to ask any questions if you have any problems!

 

[yertnamreg]

Thanks for the tip on the tires. Those and the brakes are my top priority. I'll be doing the work at a shop with another 1085 which I can use for reference.

Glad to hear there aren't any serious gotchas with the swap. I'm hoping to build an adapter or somehow modify the power and instrumentation systems so I can retain all the A1 parts. Do you have any comments on the differences between the instruments and power distribution? I'd guess much of the power distribution could be made to work by simply replacing connectors. Are the instruments CAN based?

Edit: Saw the A0 vs A1 comparison on your website and learned that they are J1708. Looks like I'll have to build a sender to get them to work. Shouldn't be too hard.

 

[FMTV Truck Sales]

Keeping the A1 instrumentation will not be possible. A0=mechanical engine=analog gauges. A1= electronic engine/J1708 bus-driven (not Can) instrumentation (some anyway). Here are two of the panels we've designed for the A1...

View attachment 711633

 

[yertnamreg]

Very nice work! I definitely wouldn't mind having one of those in my truck!!

I still think I can make the gauges work. I can read in any of the vehicle's signals with a microcontroller and supply the data to the gauges with J1708. The hardest part will be figuring out what format each gauge wants its data in. Given your dash, it looks like you already have some insight on that...

Edit: It's all J1587 right?

 

[rocket990]

Hi, do you have your cab? I bought one of those cabs and it did not come with a turret cover or door glass. It was a used 2005 cab and did not have most of the things in the photos. I bought the cab with the idea of swapping the doors and using the new style of door handles, but it came with the old style. Good luck on your swap.

 

[yertnamreg]

That's really disappointing to hear and seems downright illegal. Do we know if any of the other two buyers from that first lot of 3 had similar experiences?

I do not have mine yet, but should have it later this week. Fingers crossed everything is there. I'll be sure to post an update.

 

[scottmandu]

You take a risk with those cabs, the photos the site uses is for the only cab that they unboxed. It's obvious the units have been stealing parts off those things for some time.

 

[FMTV Truck Sales]

If still interested, you can buy a retrofit kit for the new style door handles here.

 

[pontiac62]

Be looking forward to your cab swapping write up.


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Man of few words

M1081 LVAD

 

[coachgeo]

Be looking forward to your cab swapping write up.

Make that two.

 

[Givinup]

There's an ltas a1p2 cab for sale on the big auction site for a pretty penny (or several). Bought straight from SS in Sealy from bankruptcy.

I'll be interested in seeing the cab switch!

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[NV555]

I'm picking up 2 cabs in herlong next week. I did notice that they used the same pics for every lot. If my 2 are striped or misrepresented then I'm going to refuse and contact visa.

 

[rocket990]

let know how it works out.

 

[yertnamreg]

The 1085 was delivered today!! I think it got pretty lucky!!!


Everything looks to be in really good shape. Batteries all have date codes in 2016 or 2017. Drive shafts are tight. Coolant is a beautiful shade of green, and all the other fluids look good. This truck appears to have been in service until very recently.

The truck fired right up when asked. Pulling it off the flatbed it was delivered on proved interesting without brakes. We ended up hooking a tow strap between the front tow hooks and a vehicle on the ground which acted as my brakes. I threw it in gear and backed it off their trailer without any problems.

The brake problem seems to involve the relay valve on the rear crossmember. Its completely disconnected and two of the hoses that go between the axles are missing. I'm planning on picking up some hose and fittings tomorrow and trying to get the system at least connected up how it was designed.

That said, I'm worried the system isn't building any pressure upstream. How much flow should I see coming out of the compressor? It's output seemed pretty weak (no shhhh noise was apparent). I could easily screw on the braided output line while the engine was running. I'm not experienced with air brake systems, but it seems to me that the compressor is probably unloaded and research would lead me to believe the governor is at fault. I tried monkeying with it's adjustment screw to no avail. Am I on the right track?

Cab should be delivered Monday for those following along.

Edit: More reading has led me to believe its the unloader valve. I'm going to crack open the top of the compressor and see what's going on in the morning.

 

[scottmandu]

I'm picking up 2 cabs in herlong next week. I did notice that they used the same pics for every lot. If my 2 are striped or misrepresented then I'm going to refuse and contact visa.

Good luck you will likely win that dispute but you will be banned from bidding again.

 

[yertnamreg]

I got the compressor apart this morning and it was indeed the valving in the compressor head which was causing the problem. The unloader valves were a little sticky, but the real culprit was the intake valves sticking. I hit them with a little carb cleaner and WD-40 as well as cleaned up the unloader pistons. Slapped it back together with some RTV and it was back to working.

I've got a proper unloader kit on order so I can fix the gasket I mucked up, as well as a few relay rebuild kits. Both the anti-compounding and rear booster relay looked like they could use it. I took these apart in anticipation of the rebuild and sure enough, some of the rubber bits were broken. I'm thinking I should be able to have it drivable sometime this coming week!

 

[yertnamreg]

The cab was delivered yesterday and overall I'm happy with what I got.


The cab is new and has nearly everything shown in the auction listing. I believe the only items missing are the grill and washer fluid reservoir. Looks like I got lucky!

Now to start figuring out how to make everything work on the A0 chassis...

 

[NDT]

Looking good. Let me know if the old cab & remnants or the front skid plate in the picture become available. (needing that!)