Question on transfer case speedometer drive gears

[Rembrant]

Hello again gents,

Not really a Bullnose question, but the same information should apply regardless.

The 1995 F150 chassis/driveline under my 1980 has a BW1356 transfer case? I need to swap in (I assume) a 1988-1991 BW1356 transfer case with the speedo drive in the tail shaft. They're relatively easy to find here...I know a couple guys that have at least a couple each. So the question is...by the time the late 80's rolled around...and the F150's all had 8.8 rear diffs, they were almost always 3.08 or 3.55 geared. Would the transfer case use the same speedometer drive gear for each diff option (and just change the cable's driven gear for the different ratios)? Or would there be a different drive gear in each situation?

The reason I ask is that I was reading about the M5OD trannies, and they part number or engineering number on the side of the trans refers to a specific rear diff gearing. The one in my 1984 indicates that it was designed for use with 2.73-3.08 differentials. I assumed that only meant that this is what the speedo drive gear was set-up for.

Any comments from the experts?

If I'm going to pick up a used transfer case, I'm just curious if I should look for one from a 3.55 geared truck, or does it even matter?

[Gary Lewis]

Cory - The answer is yes, there was a difference, as shown below.  But the break is in question as this says a 3.55 ratio could have either a 8 or 7-toothed gear.  

Also, note that it is for a 1345, not a 1356.  Oddly enough, the MPC doesn't list a 1356.  Nor does it have a similar table for 1989.

But, you can still use the same driven gears.  You just may run out of available gears.

[ArdWrknTrk]

Cory,
With the 1356 you can change driving gears just removing the output shaft housing.
There's a spacer clip behind the gear. Remove that, push the gear forward and remove the retainer ball from its hole in the shaft. (a magnet can help)
Slip the gear off the shaft.

Edit: they do not use the same metal sleeved gear as the 1345.

My truck uses a slip yoke and a yellow gear for 4.10:1.
If your truck has a fixed yoke then you're going to have to remove the nut from the output shaft, but it doesn't require splitting the case in either case....

I might suggest that if you do go back with a 1356, instead of a 1345, that you split the case and do the oil pump finger mod so it cannot wear through the magnesium webbing and spin with the shaft.
There's no gasket or anything to buy, just a bead of RTV on the case flange.
You will need a stout pair of snap ring pliers!

I ran into that carnage last summer, and I couldn't find a replacement.  

[Rembrant]

Awesome, thanks Jim. I didn't know the drive gear was that easy to change out...I'm not as concerned now.

The t-case in the truck has a slip-yoke. The front mounting flange of the t-case is corroded badly (there's actually a hole in it...lol) so I need to swap it out for that reason anyway, but my main concern is to get the speedo drive. The t-case works fine...I tried it out on the weekend. It surprised me a bit at just how short the throw of the shifter was...I was having trouble finding the t-case gears until I realized that all 4 positions were in about an inch of lever movement. It's all good, I just want one that fits right back in the same place and utilizes the same shifter, etc.

[ArdWrknTrk]

It's too bad the magnesium has a hole in it.
You could have just changed the tailshaft housing for one with a speedo cable hole(4 bolts!) If the '95 you have now has the ball recess in the output shaft.

I would have to look at the part breakouts to know if BW did away with the ball divot on later production.

[Rembrant]

ArdWrknTrk wrote

It's too bad the magnesium has a hole in it.

It was my fault...I hit it with the needle scaler and poked a hole in it...not realizing it was corroded as badly as it was. I can live without a speedo, but I do want it to work properly. I'll be getting antique plates for this thing, so that will require a test drive by the mechanic...so I'll need it working regardless.

[ArdWrknTrk]

If it was that corroded its probably for the best you found out when you did.

[Gary Lewis]

Yes, good you found it.

And changing the speedo drive gear on a 1345 is easy as well.  Just remember to tighten the output shaft nut.  

[Rembrant]

Do Broncos usually have the same transfer cases as the pickups?

[Gary Lewis]

It varies.  From our page at Documentation/Driveline/Transfer Cases and the Applications tab:

[ArdWrknTrk]

Broncos all used a fixed output (yoke -or- flange) and the CV double cardan joint.

So, while it may be a 208, 1345, 1356, whatever...  the output shafts differ by application.

[Rembrant]

Ahh ok, that makes sense. I was going to make a plan to get back out to the junkyard to get the transfer case out of a brick Bronco, but when I checked some pictures I took it looked like it had a flanged output, and I need a slip yoke.

[ArdWrknTrk]

If you're opening it up to fix the oil pump stay it's NBD to swap your existing slip yoke output shaft.

Another thing to check is the output bushing.
I know the one that came attached to my Zf was wobbling around.
But I think I got to it before the splines fretted too bad.

[Rembrant]

ArdWrknTrk wrote

If you're opening it up to fix the oil pump stay it's NBD to swap your existing slip yoke output shaft.

Another thing to check is the output bushing.
I know the one that came attached to my Zf was wobbling around.
But I think I got to it before the splines fretted too bad.

Yes, but I still need a tail housing with the connection for the speedo cable, etc. I did just check under the truck and confirmed (I think?) that it is indeed a BW1356. The tag is corroded away, but I could see 135 on it, right where the 1356 is supposed to be.

[ArdWrknTrk]

Yep, that's it.

What I'm saying is that if you get one from a junkyard with a speedo drive you should probably open it up to bulletproof the oil pump.

If you have it open, you could swap the tail shaft from the one you already have (as long as it has the ball dent to hold the driven gear)

[Rembrant]

ArdWrknTrk wrote

Yep, that's it.

What I'm saying is that if you get one from a junkyard with a speedo drive you should probably open it up to bulletproof the oil pump.

If you have it open, you could swap the tail shaft from the one you already have (as long as it has the ball dent to hold the driven gear)

Right. But where is the speedo drive connection? Is it in the rear casing half, or in the tail shaft housing?

[ArdWrknTrk]

If the gear is in the tail shaft housing, the cable fitting is, too.

[Rembrant]

I found this case today for $75. Supposed to get it this weekend or early next week. He says it is out of an '88-'90 that he junked for the engine and transmission. It clearly has the speedo drive as there is a VSS still installed. Does it look like a 1356 to you Jim?

[ArdWrknTrk]

It's a little tough to say for sure, without seeing all the webbing front or back.

If it stops raining I'll try to get some pics of mine that might show some of the same features.

It would REALLY help if people took a pic of the brightly color anodized build tag when they try to sell stuff online.

The year range works, <s as long as it <i>isn't electric shift, because you don't have a good front case half  to swap./s>

Edit: I'm squinting on my phone, but I'm pretty sure I see the tip of the selector arm.

Let me go lay in the mud.
BRB

[Rembrant]

According to other pics I've looked it, it appears to be correct. He said it was a floor shift. That's the end of the transmission still bolted to it, ya? Is there a gasket between the trans and t-case? If I can't buy one we have sheets of Garlock at work...