Allison power handling capabilties in a lighter vehicle?

[MaxPF]

* snipped for brevity*

The only thing in the entire setup that could be in question is the second 241, if it fails it will recieve a 271, but not before then. I had already built the 241/241 setup and ran it behind the 6.5/4L80 that was removed for the Duramax and the driveshafts were already built for this setup, so there is no reason not to see how they hold up. As I understand it is possible to limit power with EFI Live for when it's in double low range, so that will help as well.

The 271 is a stout piece, and would definitely stand a much better chance than the 241. The output shaft on the 271 is particularly impressive. It is 34 spline (well, the Ford version is anyway - the Dodge is a smaller wussy slip yoke ), compared to what I assume is a 32 spline in your 241. If you have the 241DHD from a Dodge Cummins app, then it will have a stronger 29 spline shaft. Here's a pic of the Ford 271 shaft next to a 32 spline output shaft (from a 205 in this case, but the 241 is the same diameter 32 spline):

It also has a beefy 1.5" chain, which is the same width as the 261/3XHD and 241DHD:

The possible bad news is that it would appear the front output is still only 32 spline, although I have never heard of anyone breaking it in either a 27x, 26x, or 241. Pullers and drag race guys seem to not have any real problems with them, but rock guys occasionally break the cases. I think that mostly has to do with the bending force caused by high driveshaft angles with lots of torque applied - remember these guys ALL run solid axles with a lot of articulation, as do you.

A bigger issue may be adapting it to your current 241 range box section. As it is, you will need a 29 spline Dodge input in the range box to mate to the Ally. The bigger problem is plugging your (presumably) 32 spline range box output into a 271. Even though 241's, 261/3, and 271/3's use the same planetary set, the latter case has a larger input bearing to accommodate the large 34 spline Ford input. You won't be able to simply swap a 32 spline 241 input into the case without some creativity. Maybe the 32 spline 261 input uses the same bearing? Maybe you will have to machine a sleeve? I have no idea. Also, if you do decide to mix and mismatch parts from these cases, be advised that early (before approx. 1996) 241 gears are not compatible with later 241, 26x and 27x planetary assemblies. Both the input bearing width and the gear helix angle were changed on the latter. These are obstacles you will have to overcome when your 241 bites the dust.

As for limiting the power in the ECM when in low range... I have no idea, but I know some sled pullers use low range, and I'm sure they wouldn't want their power limited. So, either the option doesn't exist, or they turn it off with a custom tune. In any case, you can always limit torque with your right foot

Finally, you won't be able to use the VSS in your 241 as your OSS into the Ally TCM. It will work right up until you put it in double low range, at which point the TCM will freak out. There's a couple ways around the issue: one solution is to run a 40 tooth reluctor and pickup on the trans output (pressed on the 241 range box input shaft) and either not connect the low range input to the TCM or reprogram the low range ratio in the TCM to 1:1.

You can make this all work, but be prepared to get creative. Speaking about creative, have you figured out how you are going to fit a suitably large radiator, IC, and the rest of the cooling stack in an S-10?

 

[DieselS10]

Thanks for the input Max, that's some good stuff.

I agree that the 271 will be my best option, the only thing that concerns me about it is that they are so WIDE. I'm not completely sure that one would fit between the frame rails, but I have a broken one from an '08 F450 that I can measure. If it won't then I guess the Dodge DHD would be the next best option?

As far as the input for the second case goes, if I don't have the equipment to pull it off, I have 2 different friends with full machine shops (the guys from Wagoner Machine Shop (WMS) if you were in the crawling scene back in the late 90's) that should be able to fix me up.

The best thing about the (huge) possibility of the second case failing is that it should only be overly vulnerable when the front case is in low range and I have very good right foot restraint, lol, so hopefully I will be able to get some use out of. Besides with that much gear reduction throttle will be pointless since it won't be capable of any speed. This is just a weekend wheeler anyway, most of it's time will be spent on the street being used as a truck. No sleds, maybe a little drag strip action, but mostly just being driven.

I am planning on adding the VSS to the rear of the tranny/front of the 1st 241 as you mentioned. The harness that I have is from a 2wd anyway, so I don't even know if i has or could easily get the low range mode from a 4wd model. So, I think that will be the simplest option that will allow everything to work properly except for the speedometer when in either low range.

I think I have the radiator on the right track, I put it in there 7 years ago for the 6.5 Detroit that was in it and it worked flawlessly even when trailer towing at 100* plus temps. and I have the factory Duramax clutch fan still on the engine with a shrould that I built and used with the 6.5, so we'll see how it does. It's the largest aluminum dual flat core radiator that would fit between the headlights. As far as the intercooler goes, I have a smaller one that was designed for a turbo charged ricer that I ran with the 6.5. It isn't nearly as large as the factory intercooler, but that isn't an option in this truck. I'm going to give it a try, but if I have issues with it I'll probably just have to check into water/meth.

Thanks for the input.

 

[THEFERMANATOR]

Couple of things come to mind for your intercooler situation. Make sure and block your EGR and cooler(I would remove the cooler and weld the up pipe at the EGR fitting to completely remove it) to help cut down on heat to remove. Also make sure that your intake pulls in fresh cool air from outside the engine bay, and that you upgrade the turbo mouthpiece to either an LBZ or a good aftermarket unit to improve airflow to the turbo. Many have ran the DURAMAX without an intercooler all together in swaps where they simply don't have the room for it. Just keep this in mind for your tuning as the DMAX before 06 didn't monitor air intake temp at the intake manifold but at the MAF, so it won't be able to compensate for the higher temps. The biggest thing is to make sure it can flow enough CFM to keep up with the turbo and engine demands. As for the radiator, if it will cool a 6.5, it will keep a DMAX ice cold as the 6.5 is MUCH harder to cool(IDI's waste more heat energy to the cooling system than the DI DMAX does).

As for reducing the power in low range, yes the ECM has those tables in it and they do reduce torque output from the factory. I know mine goes to reduced engine power once I go into 4 low, and will stay in reduced engine power until I go back to 2 hi and restart it. There is one wire you have to hook up to the ECM and TCM to trigger the 4 low signal, but you have to make sure that your ECM has an operating system that will work with a wired 4 low signal(some I beleieve receive teh 4 low signal via the J1850 data bus). Also I'm not sure if the TCM will still fuction correctly with the gear ratio changed to 1:1 or not. I know pussow over at DP swapped to a 205 behind his 6 speed and changed the ratio, but said it kept going into limp mode on him in 4 low in reverse I believe. EFILIVE only allows us to see a SMALL portion of what is in the TCM, and I beleieve he figured there must be another gear ratio limiter table or something not seen with EFILIVE that was causing it to limp in 4 low. This was a A40 6 speed TCM though, so a 5 speed could be differrent.

 

[MaxPF]

Also I'm not sure if the TCM will still fuction correctly with the gear ratio changed to 1:1 or not. I know pussow over at DP swapped to a 205 behind his 6 speed and changed the ratio, but said it kept going into limp mode on him in 4 low in reverse I believe. EFILIVE only allows us to see a SMALL portion of what is in the TCM, and I beleieve he figured there must be another gear ratio limiter table or something not seen with EFILIVE that was causing it to limp in 4 low. This was a A40 6 speed TCM though, so a 5 speed could be differrent.

I remember that thread. It was strange that it was only an issue in reverse I wonder if he was getting a weak signal from the output sensor - reverse is the lowest gear, so for a given input speed it will have the lowest output speed. Variable reluctance sensors generate stronger signals as the speed increases, so if there was a combination of too much gap between the sensor and reluctor combined with low speed at whatever speed threshold the TCM decides to use, it could be the cause of the problem...

 

[MaxPF]

Thanks for the input Max, that's some good stuff.

I agree that the 271 will be my best option, the only thing that concerns me about it is that they are so WIDE. I'm not completely sure that one would fit between the frame rails, but I have a broken one from an '08 F450 that I can measure. If it won't then I guess the Dodge DHD would be the next best option?

Depends on whether you are OK with a slip yoke. As a rule, slip yokes suck on lifted trucks with large driveshaft angles, and the DHD has a slip yoke. The nice thing about regular 241's is that you can run JB Conversions slip yoke eliminator in them. The bad thing is that the SYE is "only" 32 spline, so it will be a weak link. OTOH, if you have a buddy with turning, spline cutting, and grinding capability then they can make you a SYE shaft and tailhousing for whatever spline count you want.

The chain is the second "weak link" in a 241 compared to the others, but it is possible to retrofit the 1.5" DHD chain and sprockets into a 241. The only thing you cant change on the 241 is the case, which has less ribbing compared to the 26x and 27x cases. Not sure how big of a deal that is since I have seen ALL of the aforementioned cases broken. Hence the reason I am still going to run the 203-205, despite being heavy and long.

 

[THEFERMANATOR]

I remember that thread. It was strange that it was only an issue in reverse I wonder if he was getting a weak signal from the output sensor - reverse is the lowest gear, so for a given input speed it will have the lowest output speed. Variable reluctance sensors generate stronger signals as the speed increases, so if there was a combination of too much gap between the sensor and reluctor combined with low speed at whatever speed threshold the TCM decides to use, it could be the cause of the problem...

I know my BURB will throw an ECM code for a P0500 only in 4 low, and eems to happen in reverse more often. It's funny though because teh TCM doesn't throw it and doesn't limp, only the ECM gets mad in 4 low.

 

[DieselS10]

Couple of things come to mind for your intercooler situation. Make sure and block your EGR and cooler(I would remove the cooler and weld the up pipe at the EGR fitting to completely remove it) to help cut down on heat to remove. Also make sure that your intake pulls in fresh cool air from outside the engine bay, and that you upgrade the turbo mouthpiece to either an LBZ or a good aftermarket unit to improve airflow to the turbo. Many have ran the DURAMAX without an intercooler all together in swaps where they simply don't have the room for it. Just keep this in mind for your tuning as the DMAX before 06 didn't monitor air intake temp at the intake manifold but at the MAF, so it won't be able to compensate for the higher temps. The biggest thing is to make sure it can flow enough CFM to keep up with the turbo and engine demands. As for the radiator, if it will cool a 6.5, it will keep a DMAX ice cold as the 6.5 is MUCH harder to cool(IDI's waste more heat energy to the cooling system than the DI DMAX does).

As for reducing the power in low range, yes the ECM has those tables in it and they do reduce torque output from the factory. I know mine goes to reduced engine power once I go into 4 low, and will stay in reduced engine power until I go back to 2 hi and restart it. There is one wire you have to hook up to the ECM and TCM to trigger the 4 low signal, but you have to make sure that your ECM has an operating system that will work with a wired 4 low signal(some I beleieve receive teh 4 low signal via the J1850 data bus). Also I'm not sure if the TCM will still fuction correctly with the gear ratio changed to 1:1 or not. I know pussow over at DP swapped to a 205 behind his 6 speed and changed the ratio, but said it kept going into limp mode on him in 4 low in reverse I believe. EFILIVE only allows us to see a SMALL portion of what is in the TCM, and I beleieve he figured there must be another gear ratio limiter table or something not seen with EFILIVE that was causing it to limp in 4 low. This was a A40 6 speed TCM though, so a 5 speed could be differrent.

I have already removed the EGR mess and I built the entire lower end of the air box so that it would pull in fresh air. I am probably going to get a mouthpiece for an LBZ Kodiak, the only thing that I haven't been able to clear the hood with is the little black 6.6 box on the intake...

Good to hear on the cooling too. I had read that the 6.5 would be very difficult to keep cool and most have trouble getting a SB to cool in an S10, so I went as overboard as I could in the cooling department. I'll find the specs on my intercooler to see what kind flow numbers it has.

Thanks again for all of the input guys, keep it coming!


Max, I was able to keep the rear driveshaft angle very descent with ample wheelbase and rotating the rearend, plus it has a CV at the case, so hopefully I get some good life out of it. If I find an relatively simple SYE option I would do it though, I've been known to bend the rear shaft when playing off-road. My biggest problem with nearly everything that I do with it is that I always try to figure out how to build/design everything because I'm cheap and I enjoy the challenge. I had never even been inside an aluminum transfer case when I decided to build the 241/241 doubler, but it was fun and I learned a lot doing it. Do you think the Dodge 241DHD will live beind another range box if it's respected?

 

[MaxPF]

I know my BURB will throw an ECM code for a P0500 only in 4 low, and eems to happen in reverse more often. It's funny though because teh TCM doesn't throw it and doesn't limp, only the ECM gets mad in 4 low.

Which leads me further to thinking it's a weak signal issue with the OSS. I will have to remember to put mine a hair's width from the gear when I install it

 

[MaxPF]

Do you think the Dodge 241DHD will live beind another range box if it's respected?

Depends mostly on how you use it. Strength wise it is identical to the 261/3XHD used in DMax trucks. It has the same chain width and output shaft diameter, and as I mentioned they use the same planetary sets. Still, if you were going to go that route I would choose a 261XHD from behind a DMax and install a pump rub kit in it. The reason is simple: 241DHD's are comparatively hard to find and very expensive. 261's from DMax trucks are easy to locate and comparatively cheap. Neither has a functional advantage over the other (well, I think the DHD has a fixed front yoke, but if you are willing to run a slip yoke anyway who cares?). I never considered a 241DHD for my rig both because of the slip yoke and because of the stupid money people want for 'em. I bet if someone made 29 or 34 spline SYE shafts for the DLD case the Dodge guys would snap 'em up. Offer it in a package with the wider sprockets and chain. The price would have to be good though, since most just resort to swapping in a Ford 271

If you plan to actually wheel your rig at all you will eventually find out why slip yokes are a Bad Thing ™. High driveline angles with slip yokes always cause issues ranging from leaky seals to breaking the tailhousing or the entire case. Even street driving with enough driveshaft angle is hard on the bushings and seals. Whatever you eventually do, you should consider eliminating the slip yokes in the plan.

 

[DieselS10]

New question guys (especially Mike!)

I was reading through some old threads and read where someone had asked MikeL about running a tranny cooler only without running it through the radiator and Mike told him no that it would overheat at speeds below 35 mph.

My radiator doesn't have radiator cooling provisions and I have absolutley no room for a tranny cooler up front where they belong, so when I ran the 6.5/4L80E I mounted the oil and tranny coolers below the cab tucked up in between the frame rails with a shroulded Pema-Cool fan mounted to them. With that setup, after 2 years of daily driving and trailer towing, the tranny fluid still looked and smelled new.

Do you guys think my Allison would be OK with a rather large cooler mounted in a similar location where it allows descent airflow at speed, but runs a 2850cfm electric fan for the slow speed stuff?

 

[THEFERMANATOR]

A large cooler say an 11X11 with a fan would do the job. The problem with low speed is lack of airflow, the fan with a temp switch set at say 200 or so would do the trick I would think. Or you could go with a liquid to liquid inline cooler plumbed into the heater line.

 

[MaxPF]

The Laminova exchangers go in-line with the lower radiator hose, and they are extremely efficient. They ain't cheap, but then again neither is a good air-oil cooler.

 

[DieselS10]

They ain't cheap, but then again neither is a good air-oil cooler.

Neither is getting the Allison rebuilt, lol.

Thanks for the input guys. I'm gonna measure and see how big of a cooler I can fit in there. I know it will handle around a 14 x 20 if need be.