Put my new/used T case in. Everything went together the same as the old, now for some reason it shifts randomly at low speeds. Its even worse in four wheel drive. And when I put it in 4 high the light reads "low range". So, something seems backwards
any thoughts? Thanks
Justin.

 

Nothing a ZF5 swap won't fix haha

Sounds like the switch that tells the PCM when you're in low range is either sticking or shorting. I'm not sure how they work on these trucks. My other truck has a little ball switch on top of it that rides along the internal shift mechanism. Did you miss a plug or possibly scrape a wire while you were under there?

 

all the plugs are accounted for. I couldn't see any damaged wires. The shift plug looks like it could be plugged in either direction. Is it possible that it could be plugged in backwards? And would this cause the truck to shift erratically even when in 2x4?

 

I'm also using the Speedo gear and connector that came with the new T case. I'm wondering if I should install my old one in its place?

 

Well I have to be honest, all my experience with this is on Chevrolet trucks so its possible there's differences.

That being said, the first thing I'd check is the speedo gear, the gear that was in your truck is the right one for your truck, the one from the new case could be different and that could potentially cause problems. The gears are usually set for the rear axle ratio and tire sizes so unless the other truck was set up the same as yours that might be giving you trouble. If you're running 3.55s but the donor had 4.11s you're sending the wrong signal using the donor speedo gear.

As far as I know, the truck doesn't care if it's in 2wd or 4x4, just if it's in high or low range. Again, its a gear ratio thing. Most low ranges are approximately 2:1 so your shift points would be the same in 2wd or 4hi but way off in Low range.

Check the speedo gear first and go from there.

 

10-4. I had a feeling so I kept the old Speedo unit. I'll pop that in next. Also, I went ahead and plugged the 4x4 sensor plug in the other way and that cured the 4 wheel drive light problem. Thanks for the input!

 

Swap it for a manual transfer case. If it's trying to shift on its own it won't be long for this world.

Aside from that, you've got a short somewhere, follow the shift motor wiring and see if there's any obvious damage.

 

it is a manual T case. I guess I wasn't being to clear, my fault. I replaced my broken manual shift T case with an identical BW 1356. After that my e4od started shifting erratically. I solved the 4x4 indicator problem. Now I'm thinking I need to put my old Speedo gear back in. The one that came in the new one must be set up for different gear ratio.

 

Ok, I put the old Speedo gear and sensor back in and the trans still shifts up and down randomly at low speeds. Not sure what changed? Rear diff sensor is fairly new. Never had this issue until I put the new T case in. Any more ideas?
thanks

 

The pcm is not getting correct info from the speedo assembly or the if this has a vss it is sending flakey info or is bad. Your new transfer case can have one of three different speedo gears on the output shaft. Green yellow brown 6t 7t 8t.

 

i put my original Speedo gear back in. Its the same color as the one that came with the T case.....pink.

 

The gear I am talking about is the one in tcase not the one on the speedometer cable.

 

Oh! Well, that adds a new dynamic to my problem. You think i should see what one was in my old T case and put that one in my new one? How much of a chore is that?

 

Never mind, I know what I gotta do. Thanks.
if they are indeed different ring gears, then that should be my problem.

 

Update (if anyone is interested)
Pulled the old speedometer ring gear from my junk T case and installed it in my new one. Very easy procedure compared to some other things I've had to fix. Went to fire her up for a shake down and no go! Batteries decided to quit. put the charger on them and they will not hold. Picking up a set today and try it again tomorrow.