Novak adapt kit swap out QT to D18/20

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1978J10REDWHITE
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Novak adapt kit swap out QT to D18/20

Post by 1978J10REDWHITE »

Have a late 70’s TH400 W the QT
I saw today Novak has an adapter assembly for swap out the QT for a D18/20 T-case.
As per what I think was said, it should fit and adapt “ok" with little work as far as drivelines and proper align etc.
Of course the shift It into 4WD will be extra mod to figure out.
I am not familiar doing such a task though so need the “edu” on this adventure.
Are you familiar with these adapters and what is the reality concerning them?

thx
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tgreese
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Re: Novak adapt kit swap out QT to D18/20

Post by tgreese »

It's been discussed before.

The Dana 18 has the same problem that the Quadratrac has, ie the rear axle is constantly driven via the chain or in this case the intermediate shaft. I would guess that longevity of the best quality intermediate shaft and bearings in a V8 application is probably no better than a Quadratrac chain. Additionally, the Dana 18 is noisy, making a constant whine. The Dana 20 has gears too, and was called the "silent" transfer case when it was introduced, recognizing the noise and durability issues associated with the Dana 18. Chain drive has now entirely replaced gear driven, being both durable and much quieter. Plus they leak badly ... you can make them better but they are hard to get to seal completely - or near-completely.

If you try to source a D18, you want the later type with the "big hole" case and largest intermediate shaft. Many of these later cases were behind the T-14 in CJs, which use a 10 spline drive gear. I believe Novak requires a 6-spline drive gear, which has to match whatever case you are using. Novak has a chart that shows the different gears and many varieties of these transfer cases. https://www.novak-adapt.com/knowledge/gear-table/

Advanced Adapters has a tapered bearing conversion for the Dana 18, but it's not cheap and requires machining of the case. You may have difficulty finding a shop that will carry out the needed machining.

I would also point out that you must completely disassemble the TH400 to change the output shaft, since that's the very last part that comes out of the case.

To me, this seems at best like an expensive lateral, especially when Ramsey is making quality replacement chains.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
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Stuka
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Re: Novak adapt kit swap out QT to D18/20

Post by Stuka »

Definitely go for a D20 over a D18. I would never put a D18 in a FSJ.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
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1978J10REDWHITE
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Re: Novak adapt kit swap out QT to D18/20

Post by 1978J10REDWHITE »

tgreese wrote: Tue Jan 05, 2021 7:58 am It's been discussed before.

The Dana 18 has the same problem that the Quadratrac has, ie the rear axle is constantly driven via the chain or in this case the intermediate shaft. I would guess that longevity of the best quality intermediate shaft and bearings in a V8 application is probably no better than a Quadratrac chain. Additionally, the Dana 18 is noisy, making a constant whine. The Dana 20 has gears too, and was called the "silent" transfer case when it was introduced, recognizing the noise and durability issues associated with the Dana 18. Chain drive has now entirely replaced gear driven, being both durable and much quieter. Plus they leak badly ... you can make them better but they are hard to get to seal completely - or near-completely.

If you try to source a D18, you want the later type with the "big hole" case and largest intermediate shaft. Many of these later cases were behind the T-14 in CJs, which use a 10 spline drive gear. I believe Novak requires a 6-spline drive gear, which has to match whatever case you are using. Novak has a chart that shows the different gears and many varieties of these transfer cases. https://www.novak-adapt.com/knowledge/gear-table/

Advanced Adapters has a tapered bearing conversion for the Dana 18, but it's not cheap and requires machining of the case. You may have difficulty finding a shop that will carry out the needed machining.

I would also point out that you must completely disassemble the TH400 to change the output shaft, since that's the very last part that comes out of the case.

To me, this seems at best like an expensive lateral, especially when Ramsey is making quality replacement chains.
Looked at the Novak site and saw the adapter with newest latest Version, Looks good, yet I didn’t see them offering a “Chain”, just a conversion TH400~D20 piece.
BJ’s has an USA made chain for the QT & a (backorder) for the 4X2 converter + hubs, etc.
Weighing it all out here on The swap-out scenario VS just Redo what I have and know is plug-play, plus seals fairly well.

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Re: Novak adapt kit swap out QT to D18/20

Post by sonoraed »

I replaced the the QT after it failed twice when I was in deep snow (vacuum issues mostly) and installed a D20 behind 360/TH400 and ran for years that way, noisy but dependable, now run it with a gen III LM7/700R4 still lots of noise but works.
Back in 2019 SEMA show stopped by Advance Adapters booth and talked to the owner, he felt a D300 would be better choice, rock crawler friend of mine like the Atla$$$ TC, after a build that took 6 years to complete, working the courage to fix all the squawks.Cheers
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tgreese
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Re: Novak adapt kit swap out QT to D18/20

Post by tgreese »

1978J10REDWHITE wrote: Wed Jan 06, 2021 1:29 am ...
yet I didn’t see them offering a “Chain”, just a conversion TH400~D20 piece.
...
:?: :?: :?: What do you mean? The Quadratrac uses a chain. The Dana 18 has an intermediate gear. The problem is the heavy load from powering the rear axle, not how that load is conveyed.

Modern chain-driven transfer cases only power the front axle with the chain, and the chain lasts much much longer than the Quadratrac chain. The Dana 20 and Dana 300 geared transfer cases have an intermediate gear, like the Dana 18. Like the modern chain-driven cases, they only drive the front axle through the intermediate gear.

Powering the rear axle wears out the intermediate gear, or chain, regardless.

For a J-truck, the output offset does not matter. If you're going to buy a conversion kit, go Dana 300. I believe someone here has adapted the NP241C too, which would also be a good option IMO.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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1978J10REDWHITE
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Re: Novak adapt kit swap out QT to D18/20

Post by 1978J10REDWHITE »

Ok thx, I’ll nee top look into this mod.
thx
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JeepsAndGuns
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Re: Novak adapt kit swap out QT to D18/20

Post by JeepsAndGuns »

I would take a D20 any day over the D18. D300 would be even better.
My cherokee was a factory T400/q-trac rig. I swaped it out for a T18/D20 and never looked back.
I had no issues with the centered rear output and the offset rear axle.
79 Cherokee Cheif. MPFI 401, T18/D20, hydroboost, otherwise stock.
93 YJ. 4.0, 5 Speed, SYE, hydroboost, WJ knuckles/brakes, 8.8 rear, OME 2.5in lift, warn M10000 winch. 31x10.50's
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tgreese
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Re: Novak adapt kit swap out QT to D18/20

Post by tgreese »

JeepsAndGuns wrote: Sun Jan 10, 2021 7:14 am I would take a D20 any day over the D18. D300 would be even better.
My cherokee was a factory T400/q-trac rig. I swaped it out for a T18/D20 and never looked back.
I had no issues with the centered rear output and the offset rear axle.
I would mention - the Quadratrac won't hold up to the impact load of a manual transmission. When you go manual, you have to go to a different transfer case.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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