SOS Dana 20 install problems

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Grand_Wag_85
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SOS Dana 20 install problems

Post by Grand_Wag_85 »

Trying to install a Dana 20 into my 77. It is 99% of the way there but there is a quarter inch or so gap between the T15 and the Dana 20 that I can’t get to close. In neutral the case outputs will spin but something is causing the trans to be jammed up too. I have the top cover off the trans and everything is stuck.

Any ideas?
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!

sonoraed
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Re: SOS Dana 20 install problems

Post by sonoraed »

might look at Novak Jeep up in Utah lots of info
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tgreese
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Re: SOS Dana 20 install problems

Post by tgreese »

I would make sure the main shaft in the transmission has not migrated backwards now that it's not held in by the transfer case. In some cases, you need to put wire around the mainshaft gears and hold them forward so they don't move rearward. If the rear main bearing of the transmission is loose in the case, pretty sure there's nothing to stop it from sliding backwards. Once it moves backwards, there are plenty of things (like the blocking rings) that can slide off and down and prevent the shaft from sliding back to where it's supposed to be.

It's been a long time since I've had one of these apart, but I recall the transmission and transfer case will go together pretty easily. I have done it on my back with just my muscles. You should be able to push them together without any bolts so both surfaces touch the gasket - they should mate with no interference.

If the two won't mate, I suggest that you bring the transfer case back to the bench and examine both the back of the transmission and the mating surface on the transfer case to find what's interfering. With the transmission gears frozen, there's something between the units that's jamming the end play out of the transmission and freezing the gears. Realize that, if you have the top off, you can shift the transmission into two gears at once, and that will freeze everything. Be sure than the shift collars are in the middle of their travel, putting the transmission in neutral.
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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Grand_Wag_85
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Re: SOS Dana 20 install problems

Post by Grand_Wag_85 »

Ended up being a combination of a few things. The new transfer case was originally on a T18 so the T15 bull gear was incorrect. Swapped the T18 bull gear onto the T15 and it protruded too far out the back. The bull gear for the T18 can be made to work but I will have to mill about 1/4" off of the flange where it butts up against the transmission output bearing.

Ended up putting the original Dana 20 back on, for now.
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!
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tgreese
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Re: SOS Dana 20 install problems

Post by tgreese »

Some T-18s use the same drive gear as the T-15 (Dana 18-8-46) and others use the 18-8-31. The Dana-Spicer part number will be on the gears. Novak has a page that shows all these gears in a big table: https://www.novak-adapt.com/knowledge/gear-table/ Suspect you could change to the output gear that matches the target Dana 20 and it will go together. Both the T-18 and T-15 have the same 6-spline output, IIRC. These gears ahave different tooth angles, so making one of them work for the other application would be bad, I fear. All you should need is to swap to the gear that matches the 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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Grand_Wag_85
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Joined: Sat Aug 27, 2011 8:46 am

Re: SOS Dana 20 install problems

Post by Grand_Wag_85 »

tgreese wrote: Fri Jul 22, 2022 1:08 pm Some T-18s use the same drive gear as the T-15 (Dana 18-8-46) and others use the 18-8-31. The Dana-Spicer part number will be on the gears. Novak has a page that shows all these gears in a big table: https://www.novak-adapt.com/knowledge/gear-table/ Suspect you could change to the output gear that matches the target Dana 20 and it will go together. Both the T-18 and T-15 have the same 6-spline output, IIRC. These gears ahave different tooth angles, so making one of them work for the other application would be bad, I fear. All you should need is to swap to the gear that matches the transfer case.
I’ll take a look they the gear table. Thanks Tim
82 J10
77 J10 Golden Eagle 401
88 GW

You know it's bad when your car is on the EPA's 10 most wanted list!
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