p/t dual range binding with 3.9 diff but not 3.70

[subaruwolf]

So, as the title says, i have a part time dual range swaped into my turbo wagon. im not sure on the year of the trans.

 

the rear diff came out of an 82 gl 4spd d/r. No sticker on the diff

 

anyway, before i swapped diffs, i never noticed it binding in 4wd.. i promptly stuck it back in fwd before i drove too far.

 

after i put the new diff in 4wd binds, fwd dosn't, radda radda radda

 

3000rpm@70mph w/ 185 80 13's if it helps

[Uberoo]

did the DR come from a turbo model?

[Numbchux]

well, using a gear calculator. A 3.7 (turbo, .871 5th gear) trans with 24.65" tires would be turning about 3100 rpm at 70, whereas the 3.9 (non-turbo, .780 5th) would be turning 2900.

 

 

But, if you're binding with a 3.9 diff, and not a 3.7, than I'd say you got a 3.7 trans. And if it's a PT4WD D/R. Than it's an '85-'86 RX trans.

 

 

How did the axles work out for you? Your turbo wagon would have already had 25-spline axles, and if your donor trans had been a 3.9, it would require 23-spline axles.

[subaruwolf]

it defiantly has turbo axles.. they are huge..

 

so.. there IS a part time dual range 3.70? i did not know this.

 

and at 70, its on the low end of 3000, tach says 2900 before it drops to 69

[Numbchux]

the rpm thing doesn't really make sense. but Subaru Speedo's tend to read high....so that might be it.

 

 

if you didn't have to swap axles, it's definitely a turbo transmission. And the only combination of turbo, PT4WD, and D/R was the '85-'86 RX. So yea, it's a 3.7. Also, that means it's a 1.19:1 low range and not the 1.59 of the non-turbo cars.

[Tycho]

P/T 4wd 3.70 Dual Range with the 1.2 low range was an option on some GLs also. I have an optioned out 85 Turbo GL sedan with that trans (and an open rear diff).

 

I myself found this out when I noticed that Lo range wasn't anywhere near a 1.6 times higher engine speed for a given wheel speed ... but I didn't have an RX as it had air struts and a digi-dash.

[subaruwolf]

allright, so i swaped back in the 3.70 and it works great! and yeah.. the lo range is defiantly not from a n/a d/r..

 

 

Thanks for all your help!