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Discussion Starter #1
I'm looking to install a transmission behind my 6bt (12v VE pump). I currently have the Tf727 that came with it.

My question is, how reliable is the 4l80e behind the Cummins? I'm aware that the swap should be straight forward, Summit Racing have all the necessary parts needed to complete the swap.

Should I rebuild the Tf727 or should I invest in the 4l80e swap?

Where I'm from, Dodge transmissions are virtually nonexistent (47rh/47re/48re), otherwise this would have been the preferred choice.

The truck will be used mainly for highway driving and I'm only looking to make 400-500 hp out of it. No towing or hard launching.

Any input or feedback is highly appreciated.
 

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For you projected power level I'd guess the 4L80e would fail. Might not be the HP that would kill it but the incredible amount of torque which will be in the neighborhood of 1000 lb ft. You say it now has a TF727. Does the truck have the 3.07 gears in the differential? Most of the 4L80e's we've seen used were with 4bt's with far less power than you plan. Even the TF727 would need a serious rebuild plus a billet flex plate and very good torque converter. Just curious, if you're only doing basic highway driving why do you need 400-500 HP?
 

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Discussion Starter #3
Hi Char1355,

Thanks for the reply,

The engine and tranny came out of an 89 Dodge airplane tug truck. The differential gears are 7.16, I've replaced the whole diff for a GM 14 bolt (4.10) for better drivability.

Being that it isn't street legal, I only drove the tug truck around the block. The truck wants to go and it's really torquey but it's clearly limited by the diff gears and extra weight in the back. (the speed is limited to 55 mph).

The engine is going into a 77 Dodge Truck W200. It's already been rebuilt (stock parts only for now) and it's already mocked up into place, both differentials have been swapped to a Dana 60 front and the 14 bolt rear.

The required hp number is for the occasional street launch here and there, not serious drag racing or making passes constantly.

The plan is to break-in the engine gradually and make sure everything is seated properly. After about 2k miles or slightly more, I'll do the upgrades.

Maybe I should have cleared it up better in the original post.. Would it be better to go with the TF727 for now (especially for highway driving) and replace it later with a rebuilt Dodge tranny (I'll have to import it and it would cost a lot just for shipping, let alone the transmission), or should I buy and upgrade the 4l80e from now (i.e would it handle the extra power later)?

Thanks again
 

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Being out of the country does have it's limits. Since you have 4.10 gears you definitely need something with an OD gear for any decent highway speed unless you have huge tires. Adapting a 4L80e will be expensive and I don't think it will survive your power. The 14 bolt is going to be stressed with a 500 HP diesel. When you hit the accelerator pedal the rear tires are going up in smoke instantly. Better plan on some strong U joints and HD drive shafts. Have you possibly thought about an Allison. The 1000, 2000, and 3000 series came behind a 6bt. Of course, none of those are cheap or small. An Allison 3060 is rated at 950 lb ft input torque with options up to 1600 lb ft and came in medium duty trucks. That was a 6 speed with dual OD gears. Of course doing 4x4 with that would be an issue. The 1000/2000 came in 4x4 models. Late model GM diesel pickups use the 1000.
 

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Discussion Starter #5
Ideally I would go with a fully rebuilt 47/48RE. I wouldn't mind paying around $4k for an ATS unit for example that only requires me to install it, but shipping is ridiculously expensive.

I'll look into the Allison 3060. I might find one for relatively cheap in my local junkyard. Medium sized diesel trucks aren't really popular here, the preferred diesel trucks here are mostly the smaller 4 cylinder Isuzu/Hyundai/Toyota/Tata ones. So I might get lucky just like I got lucky with the tug truck🤞

Could you point me to specific things I should be looking for? Specific serial numbers on transmission tags maybe? And what should I look to buy/pick up if I happened to come across one (ECU, flex plate.. etc)?

Really appreciate your valuable input Charles
 

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Well, a 3060 Allison might be a tall order. As I mentioned it doesn't have a 4x4 case so you'd need a divorced transfer case. Second it is one big sucker. Weighs around 600 lbs dry and holds 29 qts of fluid. Application was medium duty trucks with various engines, some buses, and motorhomes. Requires an SAE2 transmission mount on the engine which is common for a Cummins. Here's a link to its spec sheet. https://jexler.s3.amazonaws.com/safari/data/Allison 3060 specs.pdf Below is a photo of one and the ID plate. We've had a few guys use that transmission but mostly in 1-1/2 ton trucks or RV's. The Allison 1000 and 2000 series are rated for up to 300 HP and 780 lb ft torque and maybe a bit more. They have changed some over the years but 500 HP might be a bit much on one of those. The 1000 is used behind the Chevy Duramax diesel in their pickups and has a 4x4 option. The 2000 series is just a more heavy duty version of the 1000. Physically the same size. They came in 5 and 6 speed models. Must remember these things are computer controlled. Have to be careful when looking in the salvage yard. Allison made a lot of lighter duty automatics that were used behind Cummins diesels like the AT545. Found a lot in school buses and delivery vans. Has no OD gear and very low power rating.
 

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Discussion Starter #7
Holy cow!! 600 lbs dry and 29 qts of fluid!! That has to weigh more than the engine. It's no bueno in that case.

I'll try to find a 1000 or a 2000 series Allison. It'll be a lot harder to find a GM Duramax here, but I'll look into the junked firetrucks/ambulances area.

Thanks for the tips, I'll read more in the sticky thread about Allisons. If I did find one, I'll try to get everything that's transmission related off of the donor.
 

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No, the 3060 is about half the weight of a 6bt. The 6bt weighs 1100 lbs. Nothing light about a Cummins diesel or at least the older ones. That transmission will be serious overkill for most any swap. The Allison 1000 and 2000 came in both 5 and 6 speed. Depends on which computer program they got. Those typically have the SAE3 bellhousing in commercial applications. You might have to use an outboard transmission control module. Often the Cummins had the transmission computer tied to the engine computer. That stand alone controller tends to be a bit expensive at around $1600. That's for a 6 speed. Not sure about a 5 speed. Should you find a 1000 or 2000 that is 2wd it can be converted to 4x4 by changing the rear assembly. Those parts aren't cheap either. Then you'd need a transfer case. Option would be stay with a 2wd transmission and do a divorced transfer case. By the way, what country are you in?
 

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Discussion Starter #9 (Edited)
My mistake about the weight,
I looked into the prices of standalone controllers before, they're definitely not cheap..
Is there a clear way of telling which bellhousing I'm looking at (without having to teardown the transmission)?
I'm in Saudi Arabia btw.
The reason diesel trucks aren't popular here for the average consumer here is the bad reputation they have (think old GM V8 diesels, non turbo), and gas is cheap. Unfortunately people still think diesel trucks are low on power and problematic.
The ones we get are commercial and industrial grade engines. Lots of 6ct Cummins (8.3 ISC for example) and other CAT engines (mostly for agriculture use).
The only reason I have a 6bt Cummins truck is because it's an ex military truck that was used by the US Air force in the Gulf War.
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I sort of suspected you were in Saudi Arabia but couldn't see the little flag on you post. An SAE2 and SAE3 look very much the same except SAE2 is a bit larger. If you can see 2 bolts on the unit perimeter and measure center to center the SAE2 is 4-3/4" and SAE3 is 4-3/8". Here's a chart that may be of some use.
 

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Discussion Starter #11
Good guess ;)
The chart should come in handy, that's completely new information to me.
Can't thank you enough for your help Charles.
Now I need to find an Allison transmission first..
 

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Are there any military vehicles in the salvage yards there. If so, many of those might have Cummins diesels and Allison transmissions. The 1000/2000 series wouldn't be in any super sized trucks. Those would likely be in the 3000 series if they weren't manual. Never hurts to scrounge around the junk yards. Any US military base close by? Maybe you could talk to one of the mechanics in the motor pool and they might give you some leads. The main issue with an Allison is if it needs rebuilding that can be expensive. Of course rebuilt other automatic transmissions aren't exactly cheap either.
 

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I'm going to have to counter some of char's information. First off, a 500HP diesel isn't going to stress a 14b. 14bolts have a saddle bearing on the pinion like a 9" Ford, and this makes the R&P much stronger than an equal size overhung pinion unit like the D70. In fact, the "weak" link on a 14b, which isn't weak by any stretch, are the axle shafts, and those same shafts are used in the 11-½" AAM axle. The 11-½" unit, which is used on 3/4 and 1 ton GM and Dodge diesel pickups, does NOT have a saddle bearing like the 14b. It is a conventional overhung pinion design, and neither the pinion nor the pinion shaft is any larger than the pinion and pinion shaft on the 14b. I could go into a dissertation on why larger R&P is needed for an axle rated at higher GCWR, which has to do with how much tooth contact area the load is applied to on a continuous basis to keep localized temps down for durability, but suffice it to say you won't break the R&P on a 14b and if you break a 14b shaft then you would break an identical 11-½" AAM shaft. As long as you don't plan on towing over 18k GCW or so, the 14b will be perfectly fine. Note that 18k is very conservative, as second gen Dodge guys have routinely towed mid-high 20k range with the weaker D70 without any R&P issues. While I don't mind putting more torque through an axle than it is rated for, I like to stay within the GCWR limits to get essentially indefinite life out of the axle. Also, the 14b and 11-½" AAM use the same pinion yoke, and the 11-½" axles came with 1480 u-joints, so a 1480 yoke can be installed on the 14b if you find you're eating up 1410s.

Forget a 3000 series Allison. These are just too large for a pickup, and the smallest flywheel housing they accommodate is SAE #2 which is also too large for most pickups, unless you don't mind breaking out the Sawzall on the firewall. In stock form the 1000, 2000, and 2400 series have pretty modest ratings, but GM has increased the ratings on the 1000 series to 445HP, 910lb-ft of input torque, and a GCWR of 31,300lbs. Contrary to popular belief, while the 2000 and 2400 series have higher ratings, they all are identical internally except for gear ratios and presence or absence of a park pawl in some models. The park pawl has a weight limit, so it reduces the GCWR of the trans relative to the units without the park pawl. The transmissions with the deeper 3.54 gear sets reduce upstream load, so those transmissions tend to carry higher GCWRs vs the transmissions with 3.10 gear sets. Other factors are determined by TCM programming, which is in turn based on vocational use. Any Allison can be built to handle 500HP/1000lb-ft or so, but its really best to have working torque management. Allison 1000/2000/2400s typically use SAE #3 flywheel housings in non-GM pickup applications. The GM pickup 1000's use the standard GM corporate (aka SBC/BBC) flywheel housing. There were also SAE #2 housings available for these series, but they seemed to be rarely used since the converters on these smaller Allisons fit in the smaller #3 housings. If you are DIY rebuilding an Allison and no hard parts are needed, then the cost is comparable to a 4L80E. The biggest single expense is a good triple disk torque converter. Ally's usually don't need hard parts because they are robust internally. If they do, the price really depends on whether you can locate good used parts or have to spend the money for new. FWIW, Allison wholesaler outlets are MUCH cheaper than GM dealerships when it comes to hard parts. Clutches and steels are usually obtained in aftermarket kits that come with other mods.

500 diesel HP in a 4L80E (4L85E really) is problematic because such an engine will make around 1000lb-ft or more. There are shafts available that can handle that much power, but the main limitation is the OD roller clutch. Especially the later transmissions that uses the clutches with smaller diameter rollers. The torque will eventually blow that roller clutch apart. It's also difficult to get the OD clutches to hold that much torque. It's doable, but like I said even if you get that done it will just blow the OD roller clutch apart anyway. The most tq the 4L85E handled in stock form was 520lb-ft-lbs. That was when the trans was used behind a detuned Duramax in the Express vans. The only reason it was used was because the Allison would not fit on that van chassis.

It's much easier to build a 47RH/47RE/48RE to hold the power because they came behind the Cummins as the stock trans, and the aftermarket has made huge strides to get these transmissions to survive at high power levels. If you're fine with a 4 speed automatic. I'd stick with one of those, built for your power level.
 

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Max, I didn't mean that the 14b would fail, but dumping around 1000 lb ft of torque into it will stress it. I'd most definitely agree the 3060 is way overkill in a pickup. Even a 1000/2000 will probably require some transmission tunnel mods. They are not small transmissions. Not all Allisons have a high torque rating like the latest Duramax. I believe the base transmissions only have 620 lb ft input torque rating. On the power plan, a VE pump engine has limits. Not sure if you can get one to 500 HP but that may be possible. 450 HP is probably a better target. 300 HP on a 4bt is pretty much the limit. Might be able to do 450 HP on a single turbo but twins would be nicer. Main issue with this build is going to be logistics. He's in a foreign country the other side of the world where diesel stuff is kind of rare and a long way from any parts store.
 

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Re the 14b, I understand what you're saying. My point is that it isn't being any more stressed than the larger ring gear 11-½" AAM axle would be. Now, if towing very high GCW with that power the bigger ring gear has the advantage that the load is spread out over more gear area, so overall wear will be less per mile, but again it isn't a huge factor. FWIW, Ford used their 10.5" Sterling axle, which have a weaker and less robust ring and pinion vs the GM 10.5" 14b, in their F-250 and F-350 Super Duty's, including those with diesels making 700-900lb-ft of torque. That was their ONLY axle for SRW trucks until 2017, when the Dana 275 (for F-250's with HD tow package and SRW F-350's) and Dana 300 (DRW F-350's) were brought in to cope with the increasing GCW ratings games that the big three are playing. Because of those facts I have zero concern about the 10.5" Corporate 14bff being "stressed" unless a ridiculous amount of weight is being towed. More weight than would be safe to tow with a SRW truck.

A standard spec-sheet Allison 1000 series is rated for up to 340HP, 575lb-ft maximum input torque, 660lb-ft max input torque with SEM torque limiting, 950lb-ft maximum turbine torque, and up to 30,000lbs GCWR. The 2500 has the same HP and tq ratings as the 1000 series but is rated for a maximum 33,000GCWR. The GM versions of these transmissions that are rated for over 450HP, over 900lb-ft of tq, and 31,300GCWR use the same hard parts as the standard lower-rated 1000's. The three differences are A) GM-specific torque converter (Pre-2010 GM Ally's used a standard Allison converter part number), B) GM-specific clutches, and C) GM-specific calibrations in both the TCM and ECM. The latter is the main reason the trans can handle so much extra torque. The weak period in any automatic is during shifts when energy has to be dissipated in the clutches and the clutches have to be able to overcome the applied torque and actually lock up. Once the clutches are locked they can handle much more torque without breaking free. The shift and ECM calibration is pretty basic; defuel the engine to reduce torque to the point where the clutches can actually lock during the shift, then restore the pre-shift fueling. This way, the trans clutches and TC clutch only need to handle the static 910lb-ft of torque once applied and locked up, not while slipping and trying to lock. With aftermarket goodies Allisons can handle in excess of 1500lb-ft, although once you get into the 1000+lb-ft range AND you have the shift timing and defuel reduced (i.e. for racing or sled pulling) you are going to need aftermarket input, intermediate, and output shafts made of higher strength steels. Duramax guys who race and pull and are running over 500-550HP with aggressive tunes start breaking shafts at that point. OTOH, all other light truck transmissions need high zoot billet parts at less HP and tq than the Ally, so it isn't like the trans is weak by comparison. The hardest part of running an Ally at high power and aggressive tuning is avoiding the 3-4 shift tie-up, which is what tends to break things. You can avoid it by slowing the shift speed considerably and defueling more aggressively, but then you won't be competitive in racing or pulling. This is why hard core Dmax competition guys were swapping to 47RH-48RE hybrids, and now more and more are running highly customized and expensive TH400's with lockup converters and billet everything. Those are great for racing, but lack of OD makes them less than useful on the street.

I agree with your logistics statement. That is always a problem for guys in many other countries, unfortunately.
 

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Discussion Starter #16
Char1355, MaxPF,

Sorry it took me a while to reply. I didn't have the time to do so for the past week.
Really helpful information in your replies.
I contacted a few junkyards and one of them says they think they have the transmission I'm looking for (the Allison 1000 or 2000), he's still not sure as he didn't understand where to look for on the transmission to take a pic of the tag.
He mentioned that it's from a Freightliner Truck (he doesn't know the model of the truck but from his description, I found out it's an M2 106 model and after a lot of digging online, it's true they did come with the Allison behind their engines. However, it could also be an Eaton Fuller 6 speed Auto. Here's a link Freightliner M2 106 Specifications | Freightliner Trucks
I'll try my best to go check it out this weekend or the following one. This junkyard is about an hour and half drive (one way).
I'll take pics of the transmission and the ID tags and I'll post them here as soon as I can.
Thanks again Charl1355 and MaxPF for the valuable information and discussion, I'm sure I'll be asking more questions in the near future.
 

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Like you, no telling exactly which transmission is in that truck until you look. None of those automatics are physically small, but the 1000/2000 are probably the least. We know the 3000 Allison is a big monster. The Eaton could be one of 2 models, FO-6406A-ASW or FO-8406A-ASW. Those definitely aren't small either. May be even bigger than an Allison 3000.
 

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Discussion Starter #18
Like you, no telling exactly which transmission is in that truck until you look. None of those automatics are physically small, but the 1000/2000 are probably the least. We know the 3000 Allison is a big monster. The Eaton could be one of 2 models, FO-6406A-ASW or FO-8406A-ASW. Those definitely aren't small either. May be even bigger than an Allison 3000.
Knowing my luck, I'm sure it's probably the 3000 or even the Eaton. Only one way to find out for sure though. :cry:

The trans tunnel had already been cut, we mocked up the 5.9 and Tf727 in place of the NP 435 that came with it (it had the LA 318). So, cutting up the trans tunnel a bit more shouldn't be a problem now.
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Char1355, MaxPF,

Sorry it took me a while to reply. I didn't have the time to do so for the past week.
Really helpful information in your replies.
I contacted a few junkyards and one of them says they think they have the transmission I'm looking for (the Allison 1000 or 2000), he's still not sure as he didn't understand where to look for on the transmission to take a pic of the tag.
He mentioned that it's from a Freightliner Truck (he doesn't know the model of the truck but from his description, I found out it's an M2 106 model and after a lot of digging online, it's true they did come with the Allison behind their engines. However, it could also be an Eaton Fuller 6 speed Auto. Here's a link Freightliner M2 106 Specifications | Freightliner Trucks
I'll try my best to go check it out this weekend or the following one. This junkyard is about an hour and half drive (one way).
I'll take pics of the transmission and the ID tags and I'll post them here as soon as I can.
Thanks again Charl1355 and MaxPF for the valuable information and discussion, I'm sure I'll be asking more questions in the near future.
You definitely don't want the Eaton AutoShift. They are not a true automatic. They are an automated manual transmission. In essence, they are an FSO 6 speed with no synchros, and electric servoc operating the clutch and shifter. They require very specific calibration in the ECM for defuel and shift speed synchronization. Compared to a conventional automatic like the Allison, automated manuals are rather clunky shifting, not to mention slow shifting. I wouldn't want one in a big truck, let alone a pickup.

If it's an Allison it could be either a 1000 or 2000, or a 2400. All of these big trucks use 2WD automatics, and generally they have no park pawl, so they are less than ideal for a pickup. IIRC, all the transmissions are drilled for the pawl pin, so adding a pawl wouldn't be a big show stopper IF that is the case. Another issue is gearing; the trans could either have the 3.10 gearset or the 3.54 gearset. The former is better suited for a pickup, but either will work with the right diff gearing.
 

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Max. according to Allison, the 1000, 2200, 2350, and 2550 came with a parking pawl (P on shifter). The 2100, 2300, and 2500 models use a mechanical park brake (PB on shifter). And they did make models that don't have either position on the shifter. The shifter designation would tell you if the park pawl is present. Here's a link to Allison's manual. https://www.carolinathomas.com/wp-content/uploads/2014/05/1000-2000-operators-manual.pdf
 
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