400a to 200a conversion

[Coonass77]

Hello all.
I'm about to start a 400a to 200a alternator conversion on my 2006 m1165 (sn 241xxx).
Through the homework I had done, I thought I had understood that the 200a would work with the existing 400a brackets/mounts/etc, and all I would need is a smaller diameter (7/16") long mounting bolt and a "homemade" 3/4" spacer to make up the difference between the wider spacing of the 200a mounting tabs vs the 400a tabs.

Once I got the 200a in-hand, I did some final sanity check measuring to make sure everything was going to work before I had to start manhandling those heavy beasts around..., In doing so, I seem to have uncovered an issue. I tried to sketch out the layouts between the 400a, 200a, and existing brackets/mounts as best as I could to show how each alternator fits and mounts. My layout shows and confirms the need for the 3/4" spacer. My issue comes in with the rear mounting tab - the rear 200a mounting tab seems to line up directly with the rear alternator support bracket (the one that has a 90deg "twist" in it and bolts to the engine block). So it doesn't look like the 200a can be mounted with that particular "twist" bracket.

A few notes about my sketch:
1. The left-right dimensions are to scale (1mm=2mm), but the top-bottom dimensions are not
2. I started all of my measurements at the inside of the front mounting tab of each alternator - so this is my 0mm point (BLUE line) and should be common for each alternator so that the serp belt stays aligned
3. The GREEN line shows the difference in mounting tab spacing and confirms the need for the 3/4" spacer
4. The RED box shows the interference between the 200a rear mounting tab and the existing "twist" support bracket

The "twist" bracket I have is the 400a one (pn 12460502). Is this as simple as replacing that "twist" bracket with the one specified for the 200a (pn 5935092), or are there additional brackets required for the conversion? Maybe I'm over complicating this, but I was told by two pretty reliable sources that the 200a would work with the 400a brackets, so I'm confused and wondering if I am overlooking something???

Can anyone who is familiar with this conversion provide some insight? Thanks guys!

 

[Coug]

*snip*

The "twist" bracket I have is the 400a one (pn 12460502). Is this as simple as replacing that "twist" bracket with the one specified for the 200a (pn 5935092), or are there additional brackets required for the conversion? Maybe I'm over complicating this, but I was told by two pretty reliable sources that the 200a would work with the 400a brackets, so I'm confused and wondering if I am overlooking something???

*snip*

I'm not familiar with the conversion process, but I can tell you that the 200 amp rear bracket part number you list is the older style that goes to a stud on the exhaust. I had terrible luck with mine (sheared the exhaust stud several times) and recommend if you do have to replace that bracket to use the newer version (post 196900 serial number) which is 12460273

 

[Coug]

Reading your description and looking at your image again, you are saying that you don't think the 400 amp bracket will work because it's supposed to mount at the same location as the rear tab of the 200 amp gen?

Is there not enough space for the bracket to shift back to the outside of the new tab location, approx 3/4" rearward from where it would line up with the 400 amp? If it doesn't quite reach can you elongate the hole slightly to make it work?

The 400 amp bracket appears to go to the same location as the newer version 200 amp bracket, down low at the front of the block, so other than the mounting tab, I don't see that anything else would interfere at all by just moving the top end of it slightly rearward to match the 200 amp mounting location.

 

[TOBASH]

Steve/retiredwarhorses is the man to ask about this as he told me he dislikes 400amp units and has converted them to 200amp.

 

[Coonass77]

I'm not familiar with the conversion process, but I can tell you that the 200 amp rear bracket part number you list is the older style that goes to a stud on the exhaust. I had terrible luck with mine (sheared the exhaust stud several times) and recommend if you do have to replace that bracket to use the newer version (post 196900 serial number) which is 12460273

You are correct. I had both of the 200a brackets in my notes and for some reason typed out the wrong (old) one. Thank you for catching that.

 

[Coonass77]

Reading your description and looking at your image again, you are saying that you don't think the 400 amp bracket will work because it's supposed to mount at the same location as the rear tab of the 200 amp gen?

Is there not enough space for the bracket to shift back to the outside of the new tab location, approx 3/4" rearward from where it would line up with the 400 amp? If it doesn't quite reach can you elongate the hole slightly to make it work?

The 400 amp bracket appears to go to the same location as the newer version 200 amp bracket, down low at the front of the block, so other than the mounting tab, I don't see that anything else would interfere at all by just moving the top end of it slightly rearward to match the 200 amp mounting location.

Yes, as things currently sit with the 400a installed, the twist support bracket will occupy the same physical location as the rear mounting tab on the 200a. The twist bracket isn't slotted (as best as I can tell with it still installed in the truck), so I don't think there's any adjustment that way. It's possible I could simply rotate the twist bracket rearward, but I was worried about the bracket and tabs not being flush with each other if I did that and potentially stressing and breaking the rear mounting tab when tightened everything down (the twist bracket is thick, so I don't think it's going to give at all...). Maybe that is the solution though and I was just overthinking it. Hopefully someone who has done the conversion will confirm, the last thing I want to do is snap the tab off my 200a alternator. Thanks for the thoughts, Coug!

 

[Retiredwarhorses]

You need the spacer, 200 amp rear support bracket and 200amp rod bolt…The old 400amp rear supprt won’t work.
Also remove the extra starter positive cable and extra ground cable that runs to the extra battery box ground stud.

 

[M1165A1]

Just a tip on the swap, a hoist like this one to carry the weight of the alternator as you put them in and out is the only way to do the job (unless you have a forklift!).

 

[Coonass77]

Just a tip on the swap, a hoist like this one to carry the weight of the alternator as you put them in and out is the only way to do the job (unless you have a forklift!).

Thank you. I actually have that exact hoist. I suspect it'll be challenging enough even with the hoist, I can't imagine doing it without some sort of lifting assistance.

 

[M1165A1]

Thank you. I actually have that exact hoist. I suspect it'll be challenging enough even with the hoist, I can't imagine doing it without some sort of lifting assistance.

I helped a buddy change out his 400A and I could barely lift the alternator even after it was out. That thing is heavy.

 

[Coonass77]

You need the spacer, 200 amp rear support bracket and 200amp rod bolt…The old 400amp rear supprt won’t work.
Also remove the extra starter positive cable and extra ground cable that runs to the extra battery box ground stud.

This is exactly what I was looking for, thank you! I somehow misunderstood the need for the 200a bracket, so now things make a lot more sense.

Regarding the cables, that was my understanding as well - basically both cables that connect to the rear of the 400a are not needed and get completely removed when installing the 200a. It took me a while to trace the cables with everything still installed in the truck to confirm it was the 2 rear cables, so I put this together to maybe help someone else attempting this swap. RWH or M1165A1 - if you see anything incorrect with this, please let me know.

Thanks guys, once again, this forum is awesome.

 

[Coonass77]

You need the spacer, 200 amp rear support bracket and 200amp rod bolt…The old 400amp rear supprt won’t work.
Also remove the extra starter positive cable and extra ground cable that runs to the extra battery box ground stud.

Well... I got my 3/4" spacer, 200a rear support bracket (pn 12460273), and the 7/16" bolt, so I thought I was good to go. I pulled the 400a out of my m1165 and tried to install the 200a. I found that even with the 200a rear support bracket installed, that rear support bracket still lines up perfectly with the rear mounting tab on the 200a alternator. Basically exactly what the sketch in my previous post shows. I compared the 400a rear support bracket (pn 12460502) to the 200a rear support bracket (pn 12460273) and they're basically identical. The 400a is slightly thicker and a slightly larger diameter mounting hole, but everything else is exactly the same, so where they line up in relation to the alternator is exactly the same. I'm thoroughly confused... What am I missing and how do get this 200a mounted??? Any help would be very much appreciated... Thanks!

 

[juanprado]

Look as the tm as I thought the big bracket is different in between them. Has to be a reason for different part numbers but I do not have hands on experience.

 

[Retiredwarhorses]

Well... I got my 3/4" spacer, 200a rear support bracket (pn 12460273), and the 7/16" bolt, so I thought I was good to go. I pulled the 400a out of my m1165 and tried to install the 200a. I found that even with the 200a rear support bracket installed, that rear support bracket still lines up perfectly with the rear mounting tab on the 200a alternator. Basically exactly what the sketch in my previous post shows. I compared the 400a rear support bracket (pn 12460502) to the 200a rear support bracket (pn 12460273) and they're basically identical. The 400a is slightly thicker and a slightly larger diameter mounting hole, but everything else is exactly the same, so where they line up in relation to the alternator is exactly the same. I'm thoroughly confused... What am I missing and how do get this 200a mounted??? Any help would be very much appreciated... Thanks!

So what’s the problem? Drop the 200 in and install the spacer to take up the difference of the shorter mount…

 

[Coonass77]

So what’s the problem? Drop the 200 in and install the spacer to take up the difference of the shorter mount…

The spacer fits perfectly. The problem is that the rear support bracket (pn 12460273 - #4 in the parts diagram) aligns perfectly with the rear alternator mounting tab. I'm seeing exactly what this sketch shows.

Dumb question... but is the rear support bracket actually needed when installing a 200a with the 400a main mounting bracket (pn 12446755)? If not, the 200a should bolt right up (with the spacer). But if a rear support bracket is needed, I'm not seeing how it lines up in such a way that it can be bolted together.

 

[Retiredwarhorses]

The spacer fits perfectly. The problem is that the rear support bracket (pn 12460273 - #4 in the parts diagram) aligns perfectly with the rear alternator mounting tab. I'm seeing exactly what this sketch shows.

Dumb question... but is the rear support bracket actually needed when installing a 200a with the 400a main mounting bracket (pn 12446755)? If not, the 200a should bolt right up (with the spacer). But if a rear support bracket is needed, I'm not seeing how it lines up in such a way that it can be bolted together.

im failing to see what the problem is…

 

[Mogman]

According to your drawing you will need a longer bolt than the 400A had yes?

 

[Coug]

Are you trying to say that the rear brace won't physically move the 3/8" or so at the top where the generator mounts in order to be positioned behind the mounting tab on the generator?

Have you verified that there is nothing physically interfering with the brace as it angles down to the bolt hole in the block? Or at least have the bolt into the block loose?

Did you try installing the brace onto the mount bolt for the generator before attaching the bolt to the block at the bottom end?

You say the brace looks pretty much identical to the 400 amp version. Did you order the new brace from a reputable seller, or did you purchase it through ebay or other ultimately unknown origination point where the seller might have mislabeled the part?


We're talking about approx 3/8" difference in location for the upper end. I think we're all getting confused because we don't see exactly HOW you are managing to get the upper end of the brace to only occupy the same location as the mounting tab goes, when typically the generator is installed into location, then the bolt/brace are installed after it's located in place.

 

[Asshart]

Thank you. I actually have that exact hoist. I suspect it'll be challenging enough even with the hoist, I can't imagine doing it without some sort of lifting assistance.

91B army mechanic here. We never get to use the hoist with the 400amp units so we curse our superiors and break our backs.

 

[Coonass77]

I was over thinking it. I measured everything with the 400a still mounted in the truck and the 200a not installed. They do not align perfectly and I was worried about the rear bracket not sitting flush and side loading the alternator tab. I talked to Steve at RWH and he assured me it all works out and to just install it with everything loose and then snug it all down. I did and the 200a is now installed and making power in the truck. I forgot just how much more space there is with the 200a vs 400a under the hood.

Extra benefit #1: The 200a has the over running pulley so the truck doesn't "chirp" every time I shut it off now.

Extra benefit #2: With the larger pulley on the 200a, my tach now reads correctly.

Thanks for everyone's help/suggestions (especially Steve at RWH). I apologize if I made a bigger deal out this than it actually was. You guys are great.