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-   -   NP241 Rebuild (http://www.pirate4x4.com/forum/general-4x4-discussion/201393-np241-rebuild.html)

GloNDark 12-08-2003 11:43 AM

NP241 Rebuild
 
Anyone have experience rebuilding one of these suckers?

My 97 GMC is making a grinding noise in 4x4 when coasting. The guess is the bearing that the gear rides on is hosed, and needs to be replaced.

I've been searching and searching the net for a rebuild write-up but I have yet to find one.

Anyone? :D

onetoncv 12-08-2003 01:47 PM

are you running much angle on the rear shaft ? becuase it could be making noise due to gear rattle on a float- Jess

GloNDark 12-08-2003 02:02 PM

Quote:

Originally posted by onetoncv
are you running much angle on the rear shaft ? becuase it could be making noise due to gear rattle on a float- Jess
I WISH!!! :( Unfortunately this is on my daily driver which as yet to go under the knife. :( Soon though, if I can get these little stupid things worked out. :D

I have however noticed, what I consider to be excessive play in the t-case. When in 2 wheel drive, with the front tires blocked and the rear shaft disconnected from the axle. It will move "around" much more than I would expect it too. (By around I mean as though it were worrbling around in there?)

lefthand 12-08-2003 02:05 PM

Yup. Pretty cake actually. The May 2002 of 4-Wheel and Off-Road has a re-build article, if you're a magazine collector.

This particle edition just happens to be the one I brought with me to work once upon a time and I left it in here for my *ahem* library visits.


I used a HELM manual when I re-built mine which gives a great exploded view. That's all that is necessary really, well that and torque specs.

GloNDark 12-08-2003 02:17 PM

Quote:

Originally posted by lefthand
Yup. Pretty cake actually. The May 2002 of 4-Wheel and Off-Road has a re-build article, if you're a magazine collector.

This particle edition just happens to be the one I brought with me to work once upon a time and I left it in here for my *ahem* library visits.


I used a HELM manual when I re-built mine which gives a great exploded view. That's all that is necessary really, well that and torque specs.

want to scan that sucker for me? That's right before my subscription start up. :laughing:

The rebuild kit, ain't to bad cost wise, and the manual is something I need anyway. Any idea on a good place to purchase that manual?

I asked around on another "fullsize chevy" board ;) and got this as a possible cause from a fellow member.

"Check the transfer case fluid. Sounds like either the drive gear or the driven gear needle bearings are worn out causing the chain to bind on reverse load"

seems reasonable enough. I guess tearing it out this weekend will really let me know for sure. :D

TexasBlake 12-08-2003 02:37 PM

I rebuilt my NP231. The 241 is the same except the 241 has 6 planetaries instead of 3. They also have bigger chain and sprokets. They are really simple cases, with only about 3 moving parts.

I got a rebuild kit from work (carquest) that came with the bearings and seals, just in case I had to replace some. I don't remember the customer price, but it's probably around $100. I'm sure you can return the bearings and seals you don't need. I also replaced the oil pump which was around $35 from the dealer. You can get chains at CarQuest, they are in the timing chain book and are MUCH cheaper than the dealer. I think they are around $60 list price. I can give you a part number if you want if you give me your application.

The chain is probably be your problem, it probably has lots of slack. Mine also made noise because the oil pump catch tube fell out, and was rattling on the bottom. Another thing maybe the pads on teh shift forks wearing out, those are dealer only and cost around $3.

lefthand 12-08-2003 05:26 PM

I'll get you that exploded view tomorrow afternoon. No scanner at the house and I'll be on site in the morning. Send me the e-mail address where you want it sent.

lance

GloNDark 12-09-2003 07:04 AM

Quote:

Originally posted by lefthand
I'll get you that exploded view tomorrow afternoon. No scanner at the house and I'll be on site in the morning. Send me the e-mail address where you want it sent.

lance

sweet thanks! :beer: You got mail. :D

chvy boat 12-12-2003 10:15 PM

just a thought and I hope this is not what the problem is, but, I have a 97 chevy silverado, mine started doing the same thing at around, 75,000 miles, I bought a low miles junk yard 241 and swaped it in one night just before heading out to the Dusy Ershem Trail. That did not fix it, it turned out to be rear output shaft bearing on my 4l60e tranny.

Needles to say now I am running a sm465 and for the winter project its 203/205 doubler time.:)

lt1yj 12-13-2003 09:33 AM

The 241's are extremely simple to rebuild. The exploded view mentioned earlier, and a torque spec are really all the technical info needed.

I've grabbed several cores from my local dealer that were customer change outs. All failed due to no or very little oil. The rear seal would leak slightly and the customer did not check the oil level.

I highly recommend replacing the little plastic bushings on the mode and range forks. I've personally had 1 set fail and have heard of several others. It causes the mode shaft to jump out of the sun gear and then reengage. It sounds like someone hitting the floorboards with a hammer.

Be careful when reassembling the pump and speedo housing. The seal on the pump can be easily damaged if it's not seated properly.

If the case was run low on oil make sure the pump is in useable shape. It comes apart pretty easily and you'll see scoring or dark coloration if it's been run dry.

dieselcruiserhead 12-13-2003 12:26 PM

Glo I had never been into a t-cace but bought a Chevy and Dodge NP241 with the goal to make the ultimate Chevy one with Dodge non-spip yoke parts. I was not sure what it would be like in there but everyone is right, so incredibly easy I could possibly do it blindfolded now. I would not be scared of taking it apart, go buy a rebuild and seal kit and you should be as good as new, it will include the bearings and chain.

preach 12-13-2003 12:55 PM

Quote:

Originally posted by dieselcruiserhead
Glo I had never been into a t-cace but bought a Chevy and Dodge NP241 with the goal to make the ultimate Chevy one with Dodge non-spip yoke parts.
This is what I plan on doing too since an Atlas is out of my means right now.

How are these 241s holding up when wheeling? Is it worth bothering?

I will be tbi350/700r4/241 to Ford 60s.

dieselcruiserhead 12-13-2003 02:16 PM

THe 241s are beefy, I haven't run mine yet but I did a pretty good amount of research mostly here on the PBB and people like them a lot. They are chain driven and have a little slop compared to a geared t-case but they are very well designed and the 2.72 low is killer out of the box, the best application out there... If your Fords are L-side drop then use a 241D if you can from a Cummins. it's a super heavy duty. But your 350TB/auto will be fine with any version. The Dodge ones are non slip yoke and use a bolt on flange, you'll need your yoke in the driveshaft which is the better setup of course (a lot of people spend a lot of money convert to non-slip yoke versions). There are Chevy RHD and LHD drop versions too, but they are slip yoke so go dodge if you can. The Dodge ones are clocked different so you will have to switch it to a Chevy 27 spline input gear (if that is what your 700R4's output shaft is, which it should be), slide it on with the studs removed and you can clock it however you like because it will still lubricate well because it's oilpump lubed. You will have to drill your 700R4 to make it make it bolt on but is worth is and is much cheaper rather than the chevy version with the kit. The kit is nice though especially if you need an ebrake. But a used Chevy 241 + kit = $800 probably so there might be a cheaper option for a different t-case altogether that might be a better option. As I had a Dodge 23 spline output tranny with a Dodge pattern, and I have a diesel that doesn't need the gears, I will be more than happy with my NP241 and it will bolt on and cost only $200. I also have an ebrake on my rear axle so I didn't need one on the t-case.

NP241s in regular versions are rated for 5555ft/lbs of torque. The Cummins heavy duty version is even stronger quite a bit and should be indestructable, I rarely have heard of them breaking even with Cummins'.

Whatever your engine output is, multiply it times your axle ratio and first gear and you have your total torque. You auto will suck up a lot of that torque too and the number serves as a guide, you can exceed it and be fine. But you can also break something possibly, use your best judgment but is is stronger than most factory t-cases out there and has the lowest low out of the box.

If you are looking for a R-drop one, use the Dodge one from a '87 and on pickup, they came in all models 1/2- to 1-ton. The only Chevy versions RH drop came in blazers and suburbans with the round body style. The pickup versions and anything with the late 80s through late 90s bodystle are all LHD drop. The Dodges use a 23 spline input gear but that is fine IMO, I'm using the 23 spline input with a Cummins 4BT but it should hold up fine. You can switch inputs and planetaries between all versions but the Dodge and Chevy front cases are clocked different. Also the Dodge fixed yoke will NOT fit on the Chevy slip-yoke unfortunately. The only way to get rid of the slip yoke on a Chevy is to buy the kit from highangle driveline or another source. It is very similar to the NP231 Jeep kit, these also have the pesky slip yoke too. If you need an ebrake it's got one for $99 more and works well...

Hope all this helps...

chris demartini 12-14-2003 08:24 AM

What Dodges do I look under for non slip-yoke NP241 outputs? Will the parts work on a Chevy 241? And why do you say the slip yoke is better than a fixed yoke?

preach 12-14-2003 08:35 AM

Quote:

Originally posted by chrisd
What Dodges do I look under for non slip-yoke NP241 outputs? Will the parts work on a Chevy 241? And why do you say the slip yoke is better than a fixed yoke?
I dunno the Dodge years but I do know that the dodge tail will fit the chevy. I have a line on one of each for $250 total.

I *think* he is saying that the fixed yoke is the way to go, just made it a little confusing to read.;)

Hopefully this will last me long enough to save for an atlas. Only real option for me since I need drivers drop off of the 700r4.

pcorssmit 12-15-2003 12:17 PM

Quote:

Originally posted by onetoncv
are you running much angle on the rear shaft ? becuase it could be making noise due to gear rattle on a float- Jess
Care to elaborate on this?

I'm running an '89 241C, 700, ~3" lift, stock driveshaft ('83) w/3RL at the top, and bastard 3RL/1350 at the bottom. Angle at ride height isn't too bad, but I have broken 2 slip yokes (at the injection hole, the original on the street and the 2nd was maxed out w/the rear end hanging in the air (bound up). The top angle is about 5 worse than the bottom (been too lazy to fix).

When coasting on the street, there is a nasty noise. If you are on the gas, it goes away, then comes back as soon as you let off. My old 208 did it also, as did my old 700. Is this caused by too much angle, or the out of phase joints? I should also add that I probably have a little less than optimum slip yoke engagement. I've been too lazy to fix it, since I was going to try to pick up a Dodge case to play with, as talked about in the above posts.

Thanks,

Pete

dieselcruiserhead 12-15-2003 11:04 PM

Quote:

Originally posted by gnrrpreacher


I dunno the Dodge years but I do know that the dodge tail will fit the chevy. I have a line on one of each for $250 total.

I *think* he is saying that the fixed yoke is the way to go, just made it a little confusing to read.;)

Hopefully this will last me long enough to save for an atlas. Only real option for me since I need drivers drop off of the 700r4.

Sorry I only check in here ever couple of days. The Dodge rear cover will technically fit on the Chevy housing (I am positive of this I've done it myself), however, the shift rod that controls the gears, and what range of 4WD or 2WD is in a different location. So I guarantee, the Dodge and Chevy NP241s are NOT, I repeat NOT compatible with each other. The only way to get a fixed yoke on a Chevy NP241 is to buy the kit. And I recommend Jess from Highangledriveline because he is on Pirate and has an excellent reputation and I've heard good things about the kit.

They will bolt together but the Dodge fixed yoke will NOT fit on a chevy housing, nor will the entire rear Dodge housing fit on a chevy half without major (and I mean major) aluminum fabrication. I had the same idea as you Gnrrpreacher and wasted a lot of time and money investigating it but it was not possible to have the Dodge rear on the Chevy front. Sorry! But other than that they are very similar and it seems 96% of parts are interchangable between the two. I was even able to get all of the Dodge guts to fit in the chevy version.

Also sorry if I was misread, the FIXED yoke is much better in my opinion. I snapped some photos, I wish I had an original clunky photo of the Chevy NP241. The rear slip yoke looks like one of Madonna's bras, similar to Jeep NP231, very long and pointy.. And not desirable at all for any SWB vehicle.

I put all of the photos here:
http://www.collegeinternetsolutions....eb/fj55/np241/

Hopefully they are self explanatory. I got my Dodge fixed-yoke one from a guy on PBB which I admittedly overpiad for a little but lower than 'market' price (ie if I were to go to a tranny shop). I have found them in '87 through '91 Dodges so far, all models from 1/2 to 1 ton. In chevies they were in mid '88 through '91 Blazers and later. But the '88 through '91 FS blazers and Suburbans, ONLY those with the old body style (aka passenger side drop), have a mechanical speedo while later ones (92 and on) have an electronic version. From not a whole lot later and on, they were pretty much all switched to drivers side drop in Chevies and Dodges, so if you need passenger side drop it has to be from these years. It ran late into 90's Dodge era and I believe Chevy too. In some models they were eventually replaced with the NP242, basically an electronically shifting version. Then I think the NP272 if I'm not mistaken, I believe also a similar transfer case...

And here is my Dodge NP241, again using a spare rear u-joint yoke on the front as well. The round flange (Jess can probably mate a high angle for it) fits on the front or rear too but OEM is on the front. And the input gear there is a Chevy one I put in the Dodge t-case, but in the end I decided to get a Dodge tranny instead, and simply use the OEM dodge pattern with the Dodge input (aka no tweaking or drilling required)... This is because the Dodge and Chevy NP241s are clocked different:
http://www.collegeinternetsolutions....difference.jpg

A neat thing I did was with the Dodges, the front and rear yokes are interchangable. The OEM setup is a flange (with a CV) on the front with a u-joint yoke for the rear. I used two u-joint flanges, and had custom driveshafts done with Toyota patterns on the axles and OEM Dodge ujoints on the t-case side. Hope it helps!
http://www.collegeinternetsolutions....dodge241_1.jpg

pcorssmit 12-17-2003 08:09 AM

Quote:

Originally posted by dieselcruiserhead
[B...In chevies they were in mid '88 through '91 Blazers and later. But the '88 through '91 FS blazers and Suburbans, ONLY those with the old body style (aka passenger side drop), have a mechanical speedo while later ones (92 and on) have an electronic version...[/img] [/B]
'89 Blazers and Subs are the only application for the Chevy LHD 241 w/mechanical speedo. '90-'91 had electronic speedos.

Pete

lt1yj 12-17-2003 01:37 PM

Quote:

Originally posted by dieselcruiserhead


Sorry I only check in here ever couple of days. The Dodge rear cover will technically fit on the Chevy housing (I am positive of this I've done it myself), however, the shift rod that controls the gears, and what range of 4WD or 2WD is in a different location. So I guarantee, the Dodge and Chevy NP241s are NOT, I repeat NOT compatible with each other. The only way to get a fixed yoke on a Chevy NP241 is to buy the kit. And I recommend Jess from Highangledriveline because he is on Pirate and has an excellent reputation and I've heard good things about the kit.

They will bolt together but the Dodge fixed yoke will NOT fit on a chevy housing, nor will the entire rear Dodge housing fit on a chevy half without major (and I mean major) aluminum fabrication.

I'm not sure if I understand what you're saying here but I have successfully used the front case half from a '96 Dodge NP241 and the rear case half from a '94 Chevy NP241 with no modifications. The mode and range rods are in the same locations on both cases. I also used a '96 Dodge 29 spline input and the '96 Dodge front output shaft (32 spline) with 1310 bolt on yoke.

I reused the JB Conversion short shaft kit from my '94 Chevy case with the included mechanical speedo tail housing.

I have the older JB Conversions setup with the 1/4" machined off the output yoke but otherwise the yokes would be identical.

MOGXJ44 12-17-2003 05:12 PM

Quote:

Originally posted by lt1yj
I'm not sure if I understand what you're saying here but I have successfully used the front case half from a '96 Dodge NP241 and the rear case half from a '94 Chevy NP241 with no modifications. The mode and range rods are in the same locations on both cases...
This worked because both cases are originally LH drop. Try doing the same with a LH drop/RH drop mating and you'll see the differences.
Travis

dieselcruiserhead 12-17-2003 07:00 PM

Quote:

Originally posted by pcorssmit


'89 Blazers and Subs are the only application for the Chevy LHD 241 w/mechanical speedo. '90-'91 had electronic speedos.

Pete

Good to know I think you are right about this in terms of the speedos, I believe it's true for all NP241s in Chevies whether they are RHD or LHD. Also, the NP241 was introduced in Chevies mid '88 so there are quite a few '88 models running around too. The Dodge RHD drop 241s I've seen are all mechanical speedo, and were available as early as 1987 I believe too.

The only thing though is that all these are RHD, I believe the Chevy Blazers/Suburbans were all RHD through '91(??). Because they retained the old body style (RHD) much later but the pickup trucks went to the new body style as early as '88 and even earlier I think...

dieselcruiserhead 12-17-2003 07:02 PM

Quote:

Originally posted by lt1yj


I'm not sure if I understand what you're saying here but I have successfully used the front case half from a '96 Dodge NP241 and the rear case half from a '94 Chevy NP241 with no modifications. The mode and range rods are in the same locations on both cases. I also used a '96 Dodge 29 spline input and the '96 Dodge front output shaft (32 spline) with 1310 bolt on yoke.

I reused the JB Conversion short shaft kit from my '94 Chevy case with the included mechanical speedo tail housing.

I have the older JB Conversions setup with the 1/4" machined off the output yoke but otherwise the yokes would be identical.

Good to know, I'm glad they are compatible but it must be LHD thing only. When I get a chance I'm gonna put up a web page all about NP241s to help answer some questions for in the future, and I'll definetely be looking back at this thread ;)

LoMax 12-17-2003 08:02 PM

Mech. Speedo, Either GM or Dodge
 
Just a note;
It is possible to run either a Dodge or GM NP241 (drivers side front output) and use a mechanical speedo. We (JB Conv.) had lots of guys who were finding GM 241's with drivers side; elec. speedo units but needed a mech. speedo hole to run it in their Jeeps. Same thing for late model Dodge 241's with no speedo port at all (uses diff. housing mount). Because of this, we had a special casting made that will fit either unit and it has the big hole in the side to accept the mech. speedo insert like that found on all YJ's and TJ's (except Rubicon). There is a picture of it on the web site.

SS Blazer 02-27-2008 12:32 AM

im upgrading my 87 blazer from the stock 208 to 241 rhd and am a little confused on the best route to take. im running 350/700r4/208/dana 60rh/gm 14 bolt. Is it better to get the dodge case and switch the input gear or pay the extra cash and get the slip yoke eliminator kit for the chev case??? either way im rebuilding. whats this about clocking??? is there a difference between input gears other then the spline count??? what was that about driling out the tranny????? :mr-t:

lt1yj 02-27-2008 06:16 AM

I'm not positive about the RH drop Dodge case, but the LH drop Dodge case has a different bolt pattern than the Chevy. I think the pattern was flipped and rotated but either way the Dodge case would not bolt to the Chevy adapter.

There are some internal differences between the 241 and the 241HD. I think it's mainly in the main shaft but there are also different bearings that press into the back of the sun gear shaft.

Your best bet would be to find an '88-'89 Blazer or Suburban 241 with the mechanical speedo or the '90-91 Blazer or Suburban 241 with the electronic speede and convert it with the JB parts.

I haven't done it, but I would not be surprised if you could take the Dodge 241 parts and to convert the Chevy to a fixed tail shaft. Of course, then you'd have two bastard cases.

I don't recall now what I paid for the mechanical tail housing from JB but it was pretty reasonable at the time. That was 13 years ago so take it with a grain of salt.


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