Adios Detroit Locker, your time is up!

SquareRoot

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Short back story:

Swapped in a 14FF with a Detroit Locker and 4:56 gears (CUCV) donor into my 85 K20 about a year back. At the time, I had a Turbo 400 automatic, aka "slushbox". I have always hated auto transmissions, but that's another story. Anyway, all was good except for the engine screaming at 55 mph. So, the logical choice was to kill two birds with one stone and toss the th400 and replace it with a NV4500! Ahhh, life was great......except...that obnoxious, ratcheting, clicking, banging, surging, jerking thing that happens at low speed when taking off, slowing down and especially turning. What the hells going on with that?! Just the nature of a manual transmission in an older truck I told myself. I checked and double checked and checked every part of the drivetrain once more for any slop, misalignment, out of round, worn out, defective part that would cause the issue. Nope, everything new or good as new.

Conclusion; well more of a hypothesis at the moment. The locker does NOT play well with manual transmissions on a street driven daily driver! My logic is the constant locking/unlocking, ratcheting in the locker translates directly thru the mechanical connection of the drivetrain right into the transmission. Never noticed it with the "fluid coupling" that a torque convertor provides. Ahhh, maybe that's where the "slushbox" moniker came from? Anyway, I digress.

Fortunately, I still have the SF 14bolt that came in the K20 with the OEM open differential laying around. I figured the easiest way to test my theory would be to swap the rear end and see if that solved the issue. If so, that locker is NOT going back in. It will either get replaced with an ARB or I'm looking at the Eaton Detroit TrueTrac. I'm not keen on the price of the ARB ($1100+ a compressor) for something that's not a hardcore off-road rig. I think the Limited Slip diff is more appropriate for my use and far more affordable.

I welcome opinions on that choice if anyone has experience with it.

The swap is done, except for the E-brake cable hookup and quick brake line bleeding process. Should have it back on the road Friday when I get some time. I am very curious to drive it for a few days and see how she feels. I also need to pull that front shaft before I pull a stupid and put it in 4 WD. They say 4:10 gears in back don't play well with 4:56 gears in the front? lol
 

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nvrenuf

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It’s the nature of a Detroit, it’s just more noticeable with a manual transmission.
 

Nonstop

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Check out Yukon’s version of the Detroit. My Detroit **** itself and it was time for a replacement. Yukon was cheaper and has better manners. While it is still noticeable at times, it was a big improvement over the Detroit.
 

Bextreme04

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I've got a Yukon Grizzly in my 14BFF and I only notice a bit of locking at hard turns.. no clicking or popping noises at all.
 

dvdswan

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When I had my lunchbox locker (similar to the Detroit) I just started to take corners quicker and sharper and just dealt with the tire chirp rather than the ratcheting.
 

Craig Nedrow

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I have a 14FF with a Yukon lunchbox locker, and have thrashed it for the last year and a half. I haul all the time, use it for winter driving, and other then the built in slop (part of the design), just love it. Fo fiddy fo burns the tires even steven, no bucking or noise, but when i make the turn on my somewhat steep driveway, the inside tire messes up the gravel some. Very pleased. The Spartan locker in the front, with the hubs in and in 4X4, on dry ground is noticeable, but I don't use it for that. We are getting our third winter here, and this is the truck that rescues everyone else.
 

Vbb199

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My story I guess is the same as always, you've likely heard it.

Grizzly locker in my offroad rigs Dana 60 up front.... locks like a Detroit, but has manners, Yukon duragrip in my burb... you don't even know it's there, everyone and anyone I know including myself has said, Detroits are noisy and uncomfortable on the road.

My big block c10 is getting a Yukon duragrip when the time comes.

I'd gladly take that Detroit over my offroad rig's rear axle posi, but if you decide to keep it, it's gonna inevitably get a grizzly locker like up front too.
 
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Craig Nedrow

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My story I guess is the same as always, you've likely heard it.

Grizzly locker in my offroad rigs Dana 60 up front.... locks like a Detroit, but has manners, Yukon duragrip in my burb... you don't even know it's there, everyone and anyone I know including myself has said, Detroits are noisy and uncomfortable on the road.

My big block c10 is getting a Yukon duragrip when the time comes.

I'd gladly take that Detroit over my offroad rig's rear axle posi, but if you decide to keep it, it's gonna inevitably get a grizzly locker like up front too.
Spartan makes a locker for the D60, but I am sure you probably know that
 

SquareRoot

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Like I said, I didn't mind the locker action behind the automatic. It was when I put the 4500 in that it got obnoxious. It just slams the drivetrain around like a hoe. The slop doesn't play well with the EFI either. It gets to bucking because the IAC is trying to keep up with the on/off loading.
 

SquareRoot

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Holy Shehite! Got the swap complete and went for a nice long drive today. 100% improvement! I'm amazed how that locker changed the whole feel of the truck. Amazingly the trans even shifts better!? The 4:10 gears are even better suited to the NV4500 gearing. The truck even rides better maybe because the semi float weighs 100 pounds less than the FF.
 

68post

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This all matched my experience with using a Detroit in my cab n chassis (w/14' box), nothing more surprising than going straight at a stop sign with the wheels turned before pushing in the clutch and the truck finally does turn.
Lots of popping, banging, and crunching sounds, just not at all "street friendly". But traction improved tremendously !!
 

Craig Nedrow

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NOT FOR THE STREET
 

Craig Nedrow

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Feeling the need to get up higher in the hills, Come on over and lets play!
 

Craig Nedrow

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oops, Indiana! Does Indiana have hills? got snow I bet!
 

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