i have designed, engineered, manufactured, and installed the np205 adapter to the t1000 allison. completed the trial test runs yesterday and now have a sweet bullet proof combination! efilive reprogrammed for low 4Low. love that 6spd allsion, say goodbye to the 261 or 263 tcase
http://members.shaw.ca/prs2/Picture%20010_resize.jpg

http://members.shaw.ca/prs2/Picture%20013_resize.jpg

Did u build some sort of crossmember or support for the 205 case? Just curious due the added weight of the 205 hangin on the extension housing, if they crack with the 263 what about that beast. By the way nice work.

no i did not support it, but it is something i can do bye frabricating a bracket from the adapter flange at the np205 bolt circle (use the two lower bolts) and support it to the crossmember mount. they actually crack the allison, wow!

Ok let me rephrase that, it is not necessarily the case, but the weight of the case, and a bad u-joint or carrier bearing that causes a slight driveline vibration.

i will review a tcase support. thanks for the feedback.

cool just a suggestion Like I said nice work on the truck.

yes it is something that has to be resolved. i will add another crossmember and rubber mount with a fabricated plate which will connect to the tcase adapter bottom bolt circle to support the 205 case.

Very nice!

Although I have to ask...why? Whats wrong with the NP261/263 cases? Yeah I know, aluminum, chain driven, "must be a weak POS, the NP205 will hold up much better".



I have only heard of ONE person on this forum grenading an NP261/263 behind a duramax.

JMO.

ben

my truck was a conversion, it is the last of the bulletproof riggs, it is the original 1991 crewcab with a dana 60 solid axle and came with a 4l80e tranny, 350cid gas engine, np205 case, 14 bolt full floater rear axle. i converted it with the 2006 van engine 4l80e setup, then this winter converted the wiring to support the ally 6spd but needed to keep my np205 because the output shaft for the front axle is on the right had side. the newer 261 is on the left side. hope this clears up my madness. the truck is a real sweet ride one of a kind deal.

the 261/263 is prone to wearing a hole into the side of the case which looses all the oil and eventually kills it, as i have seen during some research doing this project. there is a aftermarket fix for this problem and if i had this case i would look into this problem. just a heads up.

i guess most know about the pump rub thread

http://www.dieselplace.com/forum/showthread.php?t=125424&page=14

That would be sweet with a doubler, too. Probably a lot of overkill, but sweet none the less. Nice work.

Nice work. Definitely a bulletproof combo.

As stated a crossmember to support the 205 would be a good idea (and cheaper than fixing an Allison extension housing).

The only drawbacks I see of this are weight (which I don't think is a concern for you) and taking a hit on the gear reduction (which probably isn't an issue for you either).

I bet you could make a few bucks selling these to guys who do a SAS using a GM or Dodge D60.

i have the adapter complete on autocad so reproduction is easy, just need to find a shop to produce

The NP205 is not bullet proof. Talk with any of the gasser truck pullers that run or did run a 205 in stock trim. The problem is yes they are gear driven, but the gears are helical.
With helical gears comes thrust, this thrust with major power with split the case in half, basically destroying everything.

Sure you can put in straight cut gears, but then you'll have to put up with all the noise. There are other mods that can be done to keep the case together without putting up with the noise. What are these mods??? That's a good question, I've never experienced these problems myself so did not worry about it. Like I said above, find some open stock gas pullers as most run the 205

i have read somewhere the 205 can handle 1500ftlbs without any mods, this is what peterson has to say about the units for some reading pleasure.

http://www.4wheeloffroad.com/techarticles/drivetrain/131_0505_np205_transfer_case/index.html

for what i am going to use it for it will last a lifetime

I can't say as I've seen any cases split, but I had seen several take out a rear output shaft. Many weld up the oiling hole in the output shaft to help combat this.

You are correct in stating that the helical gears do put a thrust on the gears. A good rebuild with new needle/cage bearings and a tight idler shaft endplay will help combat some of that issue (no different than the pinion wanting to move away from a ring gear, but at least both ends of each shaft in a 205 are anchored). Alot of guys bolt in a 30 year old 205 because they are "bulletproof" and find out otherwise (mainly due to needed basic maintenance as bearings wear and snaprings weaken). There are several small things (such as new bearings, snap rings, and billet steel retainers) that can help with longevity.

http://advanceadapters.com/product/3991/(P/N-50-9510)-NP205-fixed-yoke-HD-shaft-kit.html


And yes as dmaxlover stated it is not bullet proof, but neither is a 241/263.

The NP205 is not bullet proof. Talk with any of the gasser truck pullers that run or did run a 205 in stock trim. The problem is yes they are gear driven, but the gears are helical.
With helical gears comes thrust, this thrust with major power with split the case in half, basically destroying everything.

Sure you can put in straight cut gears, but then you'll have to put up with all the noise. There are other mods that can be done to keep the case together without putting up with the noise. What are these mods??? That's a good question, I've never experienced these problems myself so did not worry about it. Like I said above, find some open stock gas pullers as most run the 205

the 205 is still #1 for many, i needed it to match my right side diff pumpkin and this was the best case choice and i have 2 of them... which was a no brainer.

1500 ft lb's huh, i find that hard to believe. I have personally seen them brake at alot less than that.

1500 ft lb's huh, i find that hard to believe. I have personally seen them brake at alot less than that.


1500ftlbs is not that hard to achieve at the transfer case. especially with an automatic and a torque converter.

Pussow, really cool rig. Do you have pics of the conversion? Fun to watch people try something different and succeed.
Ben

this is the truck

http://members.shaw.ca/peterscarfone/DMAX%20ENGINE%20CONVERSION_files/IMG_1354.jpg

http://members.shaw.ca/peterscarfone/DMAX%20ENGINE%20CONVERSION_files/1.jpg

how come you used a van engine?

thats what i found at the time. all is converted to lbz and 6spd.

the 205 is still #1 for many, i needed it to match my right side diff pumpkin and this was the best case choice and i have 2 of them... which was a no brainer.


I would of done the same thing. Just make sure you brace that thing good to the transmission, due to the extra weight.

That truck is F'in sweet dude.

pussow are you planning on pulling or racing like to see some video pulling to see how well drive train works. Nice job putting this all together

pussow are you planning on pulling or racing like to see some video pulling to see how well drive train works. Nice job putting this all together

the only thing i pull is a 28ft and my 15ft boat. the truck has a locker up front and in the rear pumpkins so it is a true 4x4. the truck really went nice with the 4l80e and hope the allison does even better. i am still completing some of the small stuff like mounting the tranny cooler lines, securing the wiring, mounting the new shift lever, transfer case shifter, and shortening the rear drive shaft. i did take it for a small 3mile test run on the front driveshaft but it only had about 1" of spline engagement so i could not push it by any means. i just wanted to see if everything shifted and worked in manual and auto mode on this 6spd. the truck is stored winters and really only used on the street, it is never abused except for the odd rip here and there when a hemi or powerstroke needs a reality check.:p:

Reality checks will come more often when you finish very thing keep us posted

Really cool truck. Still my favorite body style, although I prefer the slightly earlier grilles. Using efi live to help everything communicate and block codes?

Are you refering to mine or one of the others that's gone south?? I trashed the front half of the case,stretched the chain and had minor pump rub. It's getting rebuilt ATM but man a 205 would sure be nice :D.

Very nice!

Although I have to ask...why? Whats wrong with the NP261/263 cases? Yeah I know, aluminum, chain driven, "must be a weak POS, the NP205 will hold up much better".



I have only heard of ONE person on this forum grenading an NP261/263 behind a duramax.

JMO.

ben

Didnt Mcrat destroy one at the drag strip in Casper?

Are you refering to mine or one of the others that's gone south?? I trashed the front half of the case,stretched the chain and had minor pump rub. It's getting rebuilt ATM but man a 205 would sure be nice :D.

why would a 205 be so nice? I dont know why people get so hung up on "old-school is better". I should convert my duramax to carb, it would probably haul ass. I had an old VW that ran pretty nasty and it had a carb...

Ok sorry, so thats TWO people that Ive heard of breaking the 261/263 cases, you and mcrat. :)

It's not {old-school it better} it's better is just plain better. 205's are plain tough and cheap. I'd prefer a Stak,Atlas or Pro-Fab but I have lots 205's.
I believe if you do your research you'll see there are others that have broken case's. Ask Merchant and he can tell you about other that have destroyed the front part of the case.

why would a 205 be so nice? I dont know why people get so hung up on "old-school is better". I should convert my duramax to carb, it would probably haul ass. I had an old VW that ran pretty nasty and it had a carb...

Ok sorry, so thats TWO people that Ive heard of breaking the 261/263 cases, you and mcrat. :)

I'll take one. Nice piece you came up with.

I'm interested in what you had to do within the ECM/TCM to allow the 1.96 low range of the NP205 not to cause a code while in 4LO. Not that I'm going to do it myself, I'm just curious what needed to be done (curiosity).

Nice job on a very nice adapter and nothing like the piece of mind that will come with the 205. Not that I don't trust my push button 263 :rolleyes:.

1991 np205 from the gm crewcab came came with a speed reluctor ring and speed sensor already in the case, all you have to do is mount your 261 speed sensor into the 205 case and use efilive to reprogram tcm for the low range ratio to 1.96. your automatic selection unit on the dash would have to be aborted and a new manual stick c/w switch has to be fabricated so the ecm knows your in low range with some simple wiring mods, thats it. My next project truck will be the 2008 dmax chevy c/w solid axle coil over front end, dpf delete and np205 upgrade, but that will not be for several years.

getting back to the 261 vs 205, there is no doubt a 205 will out due any of the new gen cases when it comes to reliability. It has less parts, gear to gear (no planets, chain, or oil pump assembly), solid case steel housing, much easier to maintain... and 1000's of them out there for under $500. try buying a 261 or 263 and if you do get out $800-1000 for another case which you have to make mods to for another $300 so it will not dry up from lack of lub and grenade itself when your not in your back yard.

for anyone interested, this ebayer is selling the same unit i have with the tranny for 700, it did not sell, i bet this case can be pruchased for under $300 less the tranny. 320344634874. just make sure your truck has a right side shaft drop. if not you will have to use a dodge or ford case and modify it for a vss on the output.

The problem with that swap is that the front drive shaft is too close to the transmission. I know a guy who has done them as well.

Anyone have the adapter for sale yet? My 261 left me on the side or the road last week :mad:.

Not for a drivers side drop 205. I am working on one but I am unsure of an ETA.

Why not? Same round 6 bolt pattern on GM and Furd. Just needs a different sleeve.

Keep me posted.

Not for a drivers side drop 205. I am working on one but I am unsure of an ETA.

The problem with that swap is that the front drive shaft is too close to the transmission. I know a guy who has done them as well.


you have to clock the tansfercase, it clears without issue.

i have posted this problem i am having already but will post here too:

i have the truck running with the new allison behind it after converting it from 4l80e to the 6spd ally. the only problem is low range, my transfer case is 1.98:1 and i changed this in the tcm already. i have no problems in the forward direction and everything works fine, reverse is a different problem. if i put the tranny in reverse and i apply no accelerator the tranny trips to neutral after about 10ft, moving it back to neutral and back to reverse it will do the same thing again after 10ft. Now here is the confusing part, if i put it in reverse and slightly touch the accelerator between 800 to 1000 rpm it holds fine and stays in reverse or if you hold the brake and apply resistance in reverse without pushing the accelerator it will not trip. i have none of these problems in 4low forward or in 2hi. i even tried changing the ratio in the tcm every .02 incréments up and down but at 2.06:1 it kills forward direction 4low. and 1.96:1 kills forward also. other than the 4low reverse problem the tranny upgrade is working fine. Does anyone have a possible idea what my be going on, i am all out of them, btw it has a new tcase vss. for some reason it is torque sensative but only in 4low reverse? I am wondering if there is something else efilive cannot see in the programming end of things for a ratio change in the transfercase. just a guess cause everthing else is fine in 2hi and 4low forward, which would eliminate the tone wheel and vss on the transfercase.
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looks super, i have wondered why more people haven't done this when they kill a tcase due to pump rub issues, or doing a SAS. i have a 205 or 2 out behind my shop just for a rainy day. being able to put one in my dmax would be worth it if my tcase died!....

a good tech article would rock about this swap.

thanks

interesting problem about the reverse issue. Do you have a tech 2 so you can look at the "calculated gear ratio" data? EFILive doesnt read out many parameters for the allison...

there could very well be a separate xfer case ratio table for reverse.

Here is one other thing I can think of that you might try.

set the reverse ratio (D1205) to 6.217

ben

Ben, "set the reverse ratio (D1205) to 6.217", will this complicate 2hi mode? and you lost me this that number change, why 6.217

i can get my hands on a tech2 but will take several days.

you have to clock the tansfercase, it clears without issue.
Not really. It creates a compound angle front driveshaft issue as well as a clearance issue.

Ben, "set the reverse ratio (D1205) to 6.217", will this complicate 2hi mode? and you lost me this that number change, why 6.217

stock reverse ratio is 4.48.

x 2.72 (stock low range) = 12.18

1.96 x A = 12.18

A = 6.217


yes, it might mess things up in high range...but I figured its worth a shot?

Have you tried PM'ing the EFILive guys or posting over on their forum??

ben

yes i tried via email but still no response to date.

Not really. It creates a compound angle front driveshaft issue as well as a clearance issue.

True, but how noticeable (or should I say how much are we clocking it)?

I know clocking does not change the rear output angle any as it's a straight shot and will cause the front output to be left or right of it's original orientation (which introduces not only a vertical mismatch, but a horizontal one as well to the pinion snout of the axle).

That being said, I guarantee even factory trucks (especially those in the 80's) had compound angles from the factory. Hell my front axle in the 80 moves side to side all the time as there is play in the springs, shackles, bushing, etc. If clocking is kept to a minimum, I bet you would not even be able to notice it, hell depending on which way it goes it may even provide a better angle depending on mods already done to the truck.

I belong to a Blazer site and those guys do rock crawling and often times clock the t-case a considerable amount for ground clearance and many of them can run in 4 Hi at high speeds with little or no vibration.......and there are others who notice a slight vibration in 4 Hi at speed, but not in 4 lo (as they are likely not able to travel as fast in 4 lo).

FWIW