Getting my ducks in a row

[Shdwdrgn]

I think I found a front differential with the 4.10's for a decent price, but before I jump on it (and while I'm waiting for an answer on shipping rates), I wanted to double-check that I'm not missing anything...

Swapping from 3.42's to 4.10's - is there any difference in the encoder? Anything else I need to ensure I receive so the computer isn't confused by the gear swap?

The new diff is a 2007. Mine is a 2004. They specifically state it has the 2-bolt housing. So this should be a direct replacement? No other major changes between the years?

I assume I don't need worry about getting the PCM updated until after I get the rear axle swapped? Is this something that HPTuners can change (other than the speedometer), or am I going to have to pay for another reprogramming after the axles are changed? If I can do this from HPT, can someone with 4.10's please tell me what your numbers are?

I've found some 8.6" rear axles locally, so I'm not worried about being able to get that, but the front has been a pain to find. If I can get this now, it will give me time to go through and replace seals and clean it up while I'm waiting on cash to buy the rear.

[The Roadie]

All front diffs are the same, just like all alternators are 150A. Gm put out some false data and never bothered to retract it before the first model year.

If you don't get the TCCM reprogrammed with the gear ratio, your LO range interlock may engage at 3 MPH instead of 4. No issue there. And your A4WD clutch engagement algorithms may be slighly off, but I've already offered to fly out and slap anybody who uses A4WD mode without DAMN good reason for it and understands the risks of its operation.

I wouldn't overthink how it will work with different gears. The speedometer is highly overrated as a tool.

[NC_IslandRunner]

The speedometer is highly overrated as a tool.

The only reason I don't have the PCM tune is they can't speedo correct, But they charge the same as the TB's that they can correct. I think I should be discounted!

[The Roadie]

I think I should be discounted!

I think you should adjust your expectations and accept the many other benefits of the tune. I suspect you're just cheap.

[NC_IslandRunner]

I think I should be discounted!

I think you should adjust your expectations and accept the many other benefits of the tune. I suspect you're just cheap.

I'm not cheap, I'm married!

[navigator]

I'm cheap and married!

[Shdwdrgn]

Just to clarify... I actually HAVE HPTuners myself. I didn't mean to imply I was going to get someone else to do a PCM tune for me. So can anyone please explain to me -- does HPT also reprogram the TCCM (since it has the ability to change shift parameters and TC lockup), or is all of that stuff controlled by the PCM? If it is controlled by the PCM, then what exactly is being controlled by the TCCM?

If HPT *CAN* reprogram the TCCM, would it be possible to get a copy of someone else's full program for 4.10's, apply that, then add my own changes back in again? I've seen some folks mention that they were able to capture speedometer changes in HPT from a full program, but not from a simple update. (I hope I'm making sense?)

[The Roadie]

I've never heard of any tool other than a GM TechII that can flash or reprogram a TCCM. TCCM can't do anything to the transmission. That's only under control of the PCM. As I said, the TCCM runs the 4LO interlock because it controls the encoder motor, and the A4WD clutch positions. Thus the TCCM needs to know the front and rear driveshaft RPMs and the transfer case has the sensors for those two built in. It gets the gear shift position (for the 4LO interlock) by communicating to the PCM on the data bus.

[Shdwdrgn]

OK, so nothing to worry about. At some point I will want to get my speedometer recalibrated though. It's just one of those things I'm anal about, like having all the clocks set to the correct second. It drives me nuts that it is currently off by 2mph at 60, and I'm really going to be off after the gear swap, but I need that extra oomph for towing the trailer up the mountain.

[AWCougar]

And your A4WD clutch engagement algorithms may be slighly off, but I've already offered to fly out and slap anybody who uses A4WD mode without DAMN good reason for it and understands the risks of its operation.

hey roadie... that means i need some answers from you lol. and dont bother flying i hate runnin in it but every bump i hit in 2Hi i get a grinding noise comin from front end on passenger side... but only in 2hi... but do tell me what are the risks of its operation???

[v7guy]

Chris, I ain't Roadie, but basically, when auto 4wd engages it slams the gears into operation at wheel speed... and to make matters worse the diff is turning in the opposite direction when it engages, causing even more stress on the components.

I'm fairly confused by what you were asking in the rest of your post.

[NC_IslandRunner]

OK, so nothing to worry about. At some point I will want to get my speedometer recalibrated though. It's just one of those things I'm anal about, like having all the clocks set to the correct second. It drives me nuts that it is currently off by 2mph at 60, and I'm really going to be off after the gear swap, but I need that extra oomph for towing the trailer up the mountain.

My speedo shows 54, I'm actually going 60.

[Shdwdrgn]

My speedo shows 54, I'm actually going 60.

Trying to follow the math here... My larger tires make my speedometer read lower than actual speed, however the gear change will make my speedo read higher. So if (stock) the engine RPM runs 1627 @ 60mph, and the chart says that my adjustments will make it run 1886rpm @ 60mph, then this means my speedo will be reading almost 70 when I'm doing 60?

Yeah I'm definitely going to have to get that fixed. If for no other reason than that the warranty would run out faster on my tires due to the apparent increase in mileage.

[djthumper]

Since you have the HP Tuner I thought it was able to adjust the PCM to the new gear set for the proper reading.

[JorDaneeKey]

My speedo shows 54, I'm actually going 60.

That's it? I'm doing 64 at 54.


As for getting the speedo fixed, nothing some tape and a magic marker can't fix.

[drburke]

My replacement cluster came with the speedo off by 3 with stock tires. It.. drives.. me.. insane. Once I get the bigger tires, I'll pull the needle and replace it. It doesn't fix the mileage issue though, which I never thought about. Didn't someone here put a resistor on the VSS path to accomodate for the tires?

[AWCougar]

Oh i was just saying i get a grinding noise only when i`m in 2hi while braking at the speeds of 32-24 mph after going over a small set of bumps... we are still trouble shooting the issue. i was just curious on what the exact issue is/was... thanks for letting me know. i wasn't entirely sure as to how it worked because i am no automobile mechanic lol

[Shdwdrgn]

That front diff arrived today. Opened up the box, and from what I can see, the thing looks brand new! Somebody did a real fine job of cleaning off the case before sending it. What I can see in the box looks like the diff plus a separate short axle? Anything else I should look for before I shove it back in the corner?

Unfortunately I wrenched my back/hip badly last week... I won't be working on anything for awhile, which is a real shame. I picked up another project a couple weeks ago -- a Kawasaki KZ1000 which I plan to strip down and rebuild over the Winter. And the way I'm feeling, I can't even make it outside and *look* at what I have. Guess this gives me time on the internet to search for a rear axle for my TB.

[Trail X]

Just out of curiosity, what would you consider a good rate for a front diff? I've only seen them for as low as about $400 around here.

The short axle is your intermediate shaft... the one that runs through the oil pan and connects between the diff and the disconnect.

If you bought the front axle assembly, I would have expected a disconnect to also be in the box. Not there?

[JesterGrey]

Just out of curiosity, what would you consider a good rate for a front diff? I've only seen them for as low as about $400 around here.

The short axle is your intermediate shaft... the one that runs through the oil pan and connects between the diff and the disconnect.

If you bought the front axle assembly, I would have expected a disconnect to also be in the box. Not there?

My front diff did not come with the disconnect either. Maybe the yards that pull these parts sell the disconnect and assembly separate?
It would make sense if they did since some people have issues with the disconnects going out type thing. Im still new to all of this but figured I might throw some insight in there .