700R4/NP-205 Fluid question???

[fireman_in_tulsa]

I recently purchased a 72' 4x4 swb that was originally a stick shift. Previous owner put in a 700R4 with a BO adapter. He told me that with the automatic tranny in it that the transmission fluid will be used not only in the tranny but in the transfer case as well. He stated that the tranny fluid would inter-mingle with the gear oil and to only use automatic tranny fluid. That didn't sound right to me. Isn't the T-Case seperated from the tranny by a seal? Therefore still needing gear oil? I know that the T-Case took gear oil previously. Thanks for your help. I'm glad to be back on here. Haven't been here since 2002 when I had to sale my 72 swb 4x4 to finance my divorce, major bummer...but I bought back the same truck yesterday. I couldn't be happier.

Chuck

[CUSTOM/10]

I'm doing the same thing but with an Advanced Adapters out put saft & the stock transfer case adapter. And my set up has the seals located in the adapter. I don't know anything about the BO adapter that your using, if it has seals or not. I do know that some 205 t/c's came with trany fluid in them from the factory, but that wasn't until later than your truck. You may need to research the adapter that is in your truck to see if it has seals.

Gary

[fireman_in_tulsa]

well it looks like the adapter is a bowtie overdrive adapter does that sound right to anyone?

[coyote72]

It dosen't sound familiar to me, but I'm sure whatever adapter you have will be used with the factory 205 adapter that mounts to your crossmember. There will be a seal on either end of the spline coulpling and an 'o' ring on the transfercase input splines. I replaced my seals cause I was getting atf in my transfercase, my transfercase has gear oil. I have heard that some 205 t-cases take atf; but I run gear oil in mine.

[csb#356]

I've heard of 208s mounted behind 700r4s that use atf but have never heard of anyone putting atf in a 205. That doesn't mean it doesn't exist thought i guess. There is some seals around the coupler shaft in the adapter housing if its using the original one.

[motormilitia]

The NP-205 uses GL5 gear oil like a differential, the 700R4 uses ATF. On a stock truck, the adapter between the trans and t-case will have gaskets on both sides to prevent the oils from mixing.

[Transformula]

As a gear tech for a living, this is a general rule of thumb: If it has an aluminum case it uses ATF, and if it has a cast iron case, it uses gear oil. There are exceptions out there so don't get all over me for this one. Just a general rule of thumb for us old-schoolers. THe thought of this is that in the cast iron units, there is more lash and play and needs thick gear oil to fill the voids, and more modern aluminum cases have tighter tolerances and are fine with thinner ATF.
A lot of gear cases don't care what is in there as long as there's some lubrication for cooling. Mostly when it matters is if there's clutches or synchros that might need a friction modifier.