identify dual range

[RMS]

I could use some help identifying a dual range transmission. i see talk about 3.7s and 3.9s   and want to make sure the trans has a matching gear set to the diff in the back of my 90 loyale with 3.90s.

i have two dual ranges that have been kicking around for over a decade and couldn't begin  to say what they were pulled from.

but  they still have stickers

757751

753492

 

[FerGloyale]

Post pics.

Location of the D/R shaft, transfer end setup, and front diff stub size will all be useful in determining.  should be able to say for sure what year and gear with that info.

[RMS]

some pics

[FerGloyale]

Looks to be a standard 5spd D/R from an 85-87 GL. 88/89 would have the LO range light switch on the side, but this one it's absent.

23 spline stubs, selective 4wd (not FT w/ difflock)

[el_freddo]

How do you determine the ratio by just looking at a box @FerGloyale? Quite a skill! 

In all seriousness, “easiest” way to work it out is to engage 4wd, mark the rear output shaft, rotate the diff once, counting how many times the rear output shaft rotates.

You may have to work out what .7 of a rotation looks like to decipher between 3.7 and 3.9 (which will be closest to 4 rotations). 

Cheers 

Bennie

[RMS]

well too late for for that, trans is in the car guess ill find out when I throw the leaver. if all DL's and GL's had 3.90s I should be ok.....

[Numbchux]

2 hours ago, RMS said:

well too late for for that, trans is in the car guess ill find out when I throw the leaver. if all DL's and GL's had 3.90s I should be ok.....

3.7s definitely exist, even in the PT4WD. AFAIK, they're all in turbo cars, though, which would have 25 spline axle stubs. So if you were able to get non-turbo axles on there, you're probably OK.

[el_freddo]

4wd will probably be a hand brake kind of effect if the diffs aren’t matched. 

I believe series 1 4wd touring wagons got the 3.9 diff and the DL 3.7 (could be wrong, they could all be 3.9 in the series 1). Series 2 I’ve only ever seen 3.7s across the board for the 4wd models. 

Cheers 

Bennie

[DaveT]

I miss matched the diffs once.  4wd was pretty tricky driving.  It still helped get moving, but forget cruseing in a straight line on snow.  It wandered all over the place.  And it bound up on wet or dry pavement,  you could feel it.  A lot worse than miss matched tires.

[FerGloyale]

On 11/19/2019 at 11:21 AM, Numbchux said:

3.7s definitely exist, even in the PT4WD. AFAIK, they're all in turbo cars, though, which would have 25 spline axle stubs. So if you were able to get non-turbo axles on there, you're probably OK.

this was my reasoning fo saying it will be 3.9

Only 3.7 dual ranges in the USDM market were in RX cars, and on;y the early 85/86 models were Part time. 

Since this box has Part time transfer at the back (no side lever for diff lock)  and it's 23 spline stubs........so it's got to be from an carbed 85-87 USDM GL Wagon/Sedan/3-door

***side note.....Part time single range boxes in 3.7 ratio, with 23 spline stubs, did come in 4wd, 4cyl XT's.  Non-turbo.  But no Dual ranges so this box is not one of those.

Edited November 21, 2019 by FerGloyale

[RMS]

ah.. its installed and shifting good. thanks for the help and thankfully it was 3.90s . but I forgot to save the horseshoe that supports the front of the center console. I will bend up a new bracket or bridge the gap with some abs. what have others done ?