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[Shackeng]

There seem to be plenty of AR25's available, and I am wondering what the physical differences are. I guess that it is only a difference in the clutch and drive plates, which should be fairly easy to swap. Has anyone any experience of doing this?

[biggriffin]

You certainly like a challenge 

[Shackeng]

You certainly like a challenge 

It's what keeps me going.

[frostbite]

Why dont you write to gm or bmw and ask?

Or just buy this http://www.americanpowertrainwarehouse.com/4l30e-a4s310r-transmission-technical-manual-by-atsg-covers-bmw-cadillac-honda-isuzu-acura-90/

[zirk]

Depends what you plan to do with the box afterwards, bearing in mind high Torque Engine will eat a low Torque Autobox for breakfast.

AR25 is rated at 250Nm, AR35 is 350Nm.

[Shackeng]

Depends what you plan to do with the box afterwards, bearing in mind high Torque Engine will eat a low Torque Autobox for breakfast.

AR25 is rated at 250Nm, AR35 is 350Nm.

Yes but the case is the same, so no reason why the relevant AR35 bits should not be fitted - I think Hence my OP. If it turns out that there are differences in the rest of the unit, then it wouldn't be worth considering, but as I said, if just clutches and WHY, it may be worth it.

[frostbite]

You may also find the torque convertor is whats the limiting factor. Very easy to burn out

[Shackeng]

Well I'm still using the original that was on the AR25.

[Kevin Wood]

It's the clutch packs that are different. The torque converter is just a hydraulic coupling so pretty difficult to break. You also need to keep the torque converter from the original engine as they are specified to suit the characteristics of the engine.

I'm sure you could swap the clutches over. I think the ar35 just has a couple of extra plates in each. What else is different is anyones guess. Spacers perhaps. If you've ever stripped an automatic box to that level you'll know that just remembering how it goes back together is a formidable challenge.

[frostbite]

It may be a hydraulic coupling but it has 3 parts that turn in oposite directions, if the turbine or stator stop flowing the fluid the box is guaranteed to break

[Shackeng]

It's the clutch packs that are different. The torque converter is just a hydraulic coupling so pretty difficult to break. You also need to keep the torque converter from the original engine as they are specified to suit the characteristics of the engine.

I'm sure you could swap the clutches over. I think the ar35 just has a couple of extra plates in each. What else is different is anyones guess. Spacers perhaps. If you've ever stripped an automatic box to that level you'll know that just remembering how it goes back together is a formidable challenge.

Interesting, as the one I have just replaced the thrust washer on, supposedly an AR25 rebuilt as an AR35, has only two clutch plates, the same as in my old AR25. Was I sold an AR25 under a false pretence? I could take the pack out of the Senny box and put it in mine if it has more plates. I was waiting to fix the rest of it before removing the bell housing.

[Shackeng]

It's the clutch packs that are different. The torque converter is just a hydraulic coupling so pretty difficult to break. You also need to keep the torque converter from the original engine as they are specified to suit the characteristics of the engine.

I'm sure you could swap the clutches over. I think the ar35 just has a couple of extra plates in each. What else is different is anyones guess. Spacers perhaps. If you've ever stripped an automatic box to that level you'll know that just remembering how it goes back together is a formidable challenge.

If that refers to the clutch pack in the housing behind the pump, I guess I am now qualified.

[Kevin Wood]

I believe the clutch directly behind the pump is for the torque converter lockup, which only operates under relatively light load anyway, so it may well be that it isn't different on the AR35.

[Shackeng]

I believe the clutch directly behind the pump is for the torque converter lockup, which only operates under relatively light load anyway, so it may well be that it isn't different on the AR35.

Ah, that explains it, thanks Kevin. So I still don't know for certain whether the repaired box is an AR35. However, I will comtinue to assume it is, and put it back on so that I can drive it for sump replacement.