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Old 05-24-2018, 09:46 AM   #1
72cs20
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Rockwell T-221 durability for the long haul

Hello all,

My newly acquired 66 K20 has the stock T-221 t-case and it seems to work normally. But I've read that they may have oiling issues and get hot, which can end badly.
My intended usage for my truck will see many miles of prolonged highway travel, loaded heavy. Will this be a problem for the T-221? Or should I start looking for an NP-205 to swap in?
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Old 05-24-2018, 01:42 PM   #2
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Re: Rockwell T-221 durability for the long haul

I have run one for about 80k behind a cummins 4bt and have had no problems, but if you plan to run highway speeds, 70+ loaded heavy for prolonged travel it will get hot, so an NP205 upgrade would be wise.
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Old 05-24-2018, 06:43 PM   #3
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Re: Rockwell T-221 durability for the long haul

I have been running my 62 for about 10 years now. Not a lot of miles, but a few times a year, I make 120 mile highway trips. I havent had a problem. I max out at about 55-60 mph - its a k-20. I would say keep the oil level up and the input shaft bearings fresh. They make a "high oil level kit" which is a street elbow that goes where the fill plug is. Let's you keep the oil level about an inch or so higher. I'm not running one, but plan to. I think the problem is they leak, and when the oil gets low, they fail. Good luck with yours.
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Old 05-24-2018, 07:45 PM   #4
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Re: Rockwell T-221 durability for the long haul

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I have been running my 62 for about 10 years now. Not a lot of miles, but a few times a year, I make 120 mile highway trips. I havent had a problem. I max out at about 55-60 mph - its a k-20. I would say keep the oil level up and the input shaft bearings fresh. They make a "high oil level kit" which is a street elbow that goes where the fill plug is. Let's you keep the oil level about an inch or so higher. I'm not running one, but plan to. I think the problem is they leak, and when the oil gets low, they fail. Good luck with yours.
I have made 800 mile highway trips towing but usually only tow at 55 to 66 mph. You want to keep the shaft speed of the rockwell at 2500 or lower to help keep it cool. synthetic oil in it also helps as well as Lucas synthetic gear additive.
loaded heavy and extended highway speed are what will cause him problems if it was just a daily driver with light towing or occasional heavy towing as I do I would say keep the rockwell.
Sorry for all the edits.
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Old 05-24-2018, 08:14 PM   #5
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Re: Rockwell T-221 durability for the long haul

Thanks for the replies guys.

I am putting this truck together for travel into the back country. It will be carrying my All Terrain pop up camper and all the stuff you would carry for remote travel. I estimate a load of 2200 to 2500 pounds. This would mean long stretches of highway or interstate travel to reach these destinations or trailheads.

I would like to be able to do sustained 65-70 mph speeds where possible. So I would like to have the strongest drivetrain possible without breaking the bank. I just wasn't sure how the 221 would handle such use.
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Old 05-24-2018, 08:27 PM   #6
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Re: Rockwell T-221 durability for the long haul

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Thanks for the replies guys.

I am putting this truck together for travel into the back country. It will be carrying my All Terrain pop up camper and all the stuff you would carry for remote travel. I estimate a load of 2200 to 2500 pounds. This would mean long stretches of highway or interstate travel to reach these destinations or trailheads.

I would like to be able to do sustained 65-70 mph speeds where possible. So I would like to have the strongest drivetrain possible without breaking the bank. I just wasn't sure how the 221 would handle such use.
For that use I would not be worried about a good rockwell t221 case.
I would use fresh input shaft bearings and adjust the preload on the rest of the bearing if they are in usable condition new seals and synthetics and you will be good to go.
I consider 8 to 10k loaded heavy not 2500lbs.
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Old 05-25-2018, 12:01 AM   #7
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Re: Rockwell T-221 durability for the long haul

Good. I'd rather not get into swapping out drivetrain if it isn't necessary. My project 62 is about done and I'd like to keep this on the simpler side.
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Old 05-25-2018, 06:01 PM   #8
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Re: Rockwell T-221 durability for the long haul

I agree with others here that main problem usually low oil. Make sure bearings are in good shape ( if you can't find local, try Torque King 4x4, they have lots of stuff for your 221, and your closed knuckle front axle) Also change all gear oil regularly and use a magnetic plug to get an idea of whats going on inside. ( I always weld a drain plug bung into my Eaton rear ends, like the rest of the running gear they last forever if kept full of CLEAN oil)
These trucks are made to work hard and with a little care are very reliable.
Have fun out on the trails,
Tom
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Old 05-25-2018, 11:08 PM   #9
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Re: Rockwell T-221 durability for the long haul

Thank you to all for your inputs. I appreciate it.

Short, thanks for the comment on my other thread too.

When it comes to prepping a 60-66 truck for what I like to do, I've been down this road before. The 65 Carry-All in the photo below was bone stock when I bought in 1996 from the second owner. When a year later the V6 gave up I went through the whole truck. In went a 350, disc brake Dana 44 and a Dana 60 rear with 3.73 gears. The SM420 and T-221 were swapped for an SM465/205. It was a real nice driving rig. We did many a mile all over the west in that Jimmy, including a lot of dirt and rock.
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I'm thinking of going the same route with this K20, except this time leaving the 420 & 221 in place and see how it works out.
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Old 05-31-2018, 07:00 PM   #10
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Re: Rockwell T-221 durability for the long haul

The T-221 is a great case and will do what you need.

I had a 60 frame that I placed a 69 body on and installed a 375HP 350 in it with a SM465. 4.11 gears and 33" tires. I ran 75-80 MPH all the time in it for long distances, then used it on the farm to pull grain wagons from the field to the farm or to the grain elevator.

The only issues I had was that it leaked oil ALL THE TIME. The gear oil would seep through the shims on the side. I caulked the outside of everything in an attempt to keep it in.

I tried the "overfill" thing by parking it on a sidehill, then filling it a bit more, then driving it. Unfortunately, it puked out all the extra oil from the vent plug on the top of the housing, so it coated the underside of the truck in gear oil.

IMO, it's a HD T-Case and will withstand everything you give it. I also had (3) spares in the basement.......
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Old 06-04-2018, 11:08 PM   #11
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Re: Rockwell T-221 durability for the long haul

As many have said here, the little Rockwell can be run somewhat hard if taken care of, sealed VERY well, synthetics and an extra quart doesn't hurt either. I ended up swapping mine out with a 205 out of a Dodge (divorced) because I didn't have the means to go through the 221 at the time. It was starting to leak pretty bad which led to getting hotter than I was comfortable with.

For several years, I towed a 4500# boat + 1500# in the bed in 3-4 hour stretches at 70 - 75. This was behind a mild 396.

Only toward the end did it start making a little more noise than normal. Thus the swap.

Although the 221's design lends it to running hotter than the 205, it is still a good case if set up right and can work quite well for most all jobs. The 205 is a little overkill unless you have a good one sitting around just waiting to be popped in (which I did and even then it didn't just "pop" right in. It was a lot of work).

My 221 is still patiently waiting for some attention under the work bench. Every once in a while it reminds me by jumping out and stubbing my toes for me.

Make every effort you can to get some good bearings into it which will help keep the seals in one piece and then put some thought into the extra quart of oil and better venting. I ran +1 qt for a while with no issues and it made a difference.
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Old 06-05-2018, 06:26 PM   #12
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Re: Rockwell T-221 durability for the long haul

Never heard the +1 oil trick mentioned here, I like it. So just a street 90 with a plug in the top gets it high enough, or is there more? Vent upgrades?
While I love the fact that your truck is still so original, if you do swap stuff out, please consider offering for sale on this site, as I'm sure others (myself included) could use.
Please don't think I'm preaching here, as my truck is certainly not as it left Fremont back in 65, so I will not be casting stones!
Have fun with the project, hope to see you on the trail,
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Old 06-05-2018, 09:54 PM   #13
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Re: Rockwell T-221 durability for the long haul

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Never heard the +1 oil trick mentioned here, I like it. So just a street 90 with a plug in the top gets it high enough, or is there more? Vent upgrades?
While I love the fact that your truck is still so original, if you do swap stuff out, please consider offering for sale on this site, as I'm sure others (myself included) could use.
Please don't think I'm preaching here, as my truck is certainly not as it left Fremont back in 65, so I will not be casting stones!
Have fun with the project, hope to see you on the trail,
Tom
I had used a street L + a 3/4" hose barb with about a 2" piece of some clear (poly something or other) tubing on top. It was capped with another HB and a 3/4" cap. Venting was an issue and it would puke some out occasionally. This was an issue I thought could be overcome during a rebuild but never got there.

I kept running dino in it and it kept leaking but I always knew what the level was with the clear tube.

Had the bearings been new, the seals would have held and I would have spent the scratch on some Amsoil, Redline or even Motul synthetic. Im certain it would have run somewhat cooler.... even without the extra quart because that darned idler gear would have stayed well lubed.

Ill go out in a minute and see if I have a pic of the hokey sight tube that I rigged up.
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Old 06-05-2018, 10:15 PM   #14
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Re: Rockwell T-221 durability for the long haul

Here's a pic of the hokey sight tube. IMO, with the extra oil inside, enough was thrown up at the vent baffle to get out. Extra baffles might control the oil.

Also the seals that I picked up at NAPA. Same SKF part #s for all 3.

Please excuse the mess. Lol, still working on my 10 year plan of organizing the garage.
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NV4500 Reverse Build Thread http://67-72chevytrucks.com/vboard/s...=reverse+build

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Old 06-05-2018, 11:26 PM   #15
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Re: Rockwell T-221 durability for the long haul

If you over fill it comes out the vent is my experience, I just keep it full and run synthetic 75-90w Valvoline and Lucas synthetic additive, seems to work fine.
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Old 06-10-2018, 12:48 AM   #16
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Re: Rockwell T-221 durability for the long haul

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Originally Posted by '63GENIII View Post
As many have said here, the little Rockwell can be run somewhat hard if taken care of, sealed VERY well, synthetics and an extra quart doesn't hurt either. I ended up swapping mine out with a 205 out of a Dodge (divorced) because I didn't have the means to go through the 221 at the time. It was starting to leak pretty bad which led to getting hotter than I was comfortable with.

For several years, I towed a 4500# boat + 1500# in the bed in 3-4 hour stretches at 70 - 75. This was behind a mild 396.

Only toward the end did it start making a little more noise than normal. Thus the swap.

Although the 221's design lends it to running hotter than the 205, it is still a good case if set up right and can work quite well for most all jobs. The 205 is a little overkill unless you have a good one sitting around just waiting to be popped in (which I did and even then it didn't just "pop" right in. It was a lot of work).

My 221 is still patiently waiting for some attention under the work bench. Every once in a while it reminds me by jumping out and stubbing my toes for me.

Make every effort you can to get some good bearings into it which will help keep the seals in one piece and then put some thought into the extra quart of oil and better venting. I ran +1 qt for a while with no issues and it made a difference.
I don't mean to threadjack, but is there a thread somewhere where you documented the process for swapping out the T221 for the NP205?

As far as lubrication in the T221, I was considering using the Lucas hub oil. We've used it on the crane planetarys and noticed a 40-50 degree temp drop over the syn. 85-140. The only bad characteristic we've noticed is that it likes to "climb" out of the breather.
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Old 06-17-2018, 04:59 PM   #17
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Re: Rockwell T-221 durability for the long haul

Thanks for all the input everyone. I'm going to go with the stock drivetrain for now and see how it works out. The only immediate modification I will do is to install a dual reservoir master cylinder and booster for the braking system. Power steering is a strong maybe.

To make it roadworthy I need to go through the front axle first. It definitely needs drivers side king pin bearing work, so might as well go through the whole thing. Also needs a steering box re-build.

'63GENIII, I've read your posts on all the work you've done to your 63. Well done. Excellent information. I may have to steal some of those ideas!
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Old 06-17-2018, 08:27 PM   #18
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Re: Rockwell T-221 durability for the long haul

Hi. I found the parts list that shows the "high oil level" elbow, if anyone is interested...numbers 197-199.
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Old 06-19-2018, 03:05 PM   #19
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Re: Rockwell T-221 durability for the long haul

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Hi. I found the parts list that shows the "high oil level" elbow, if anyone is interested...numbers 197-199.
Nice. What book is that out of, factory or aftermarket? I think my local Ace Hardware stocks that 'kit'
Thanks, Tom
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Old 06-20-2018, 01:23 PM   #20
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Re: Rockwell T-221 durability for the long haul

Had one of those on mine. Just a pipe 90* nipple. Took it off. Fix your leeks and you won't have a problem.
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Old 06-22-2018, 01:14 PM   #21
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Re: Rockwell T-221 durability for the long haul

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Nice. What book is that out of, factory or aftermarket? I think my local Ace Hardware stocks that 'kit'
Thanks, Tom
Somewhere along the line, I found a parts book - that's where it is from. The book has all the part numbers for the bearings, seals, etc. I am unable to attach it here, but if you PM me with your e-mail, I will send it along.

I agree, the best solution is to fix the leaks. I am pretty much there, but it still loses about 1/4" over a year or so. Haven't had the time to break it all down and re-seal everything.

Still, being paranoid about the oil level, and the scarcity of parts, I am still considering a high level kit. The street elbow only adds about an inch or so...I was thinking of using a street tee with a sight plug in the end to be able to easily see the level without pulling the plug....
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Old 06-26-2018, 01:04 AM   #22
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Re: Rockwell T-221 durability for the long haul

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Somewhere along the line, I found a parts book - that's where it is from. The book has all the part numbers for the bearings, seals, etc. I am unable to attach it here, but if you PM me with your e-mail, I will send it along.

I agree, the best solution is to fix the leaks. I am pretty much there, but it still loses about 1/4" over a year or so. Haven't had the time to break it all down and re-seal everything.

Still, being paranoid about the oil level, and the scarcity of parts, I am still considering a high level kit. The street elbow only adds about an inch or so...I was thinking of using a street tee with a sight plug in the end to be able to easily see the level without pulling the plug....
Thanks for the offer, but was just wondering if that mod was something Rockwell, Chevy or the aftermarket came up with.
Will be going through mine soon, not leaking, but at least one bearing was screaming at me and did not want to wait til it self destructed. It and a spare case are on the bench awaiting surgery, should be able to make at least one good one out of the two.
Thanks to the magic of a divorced case, and a spare 2wd drive shaft, the truck is still on the road (just not off road for now)
Interesting idea about the sight glass. Post a picture if you ever wind up doing that.
Tom
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Old 08-29-2018, 09:40 PM   #23
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Re: Rockwell T-221 durability for the long haul

My T-221 seems to want to leak and when we replaced the rear output shaft seal, there was a fair bit of metal in the lube. Still leaking after the seal replacement, so I think I’ll have to go deeper and replace bearings and seals to tighten up the leaks. Doesn’t seem to be any noisier though, so I hope it can be saved.
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