99 tahoe blowing t case fuse & no reverse

[breazin]

Ok guys,
I'm new here so bare with me please.

99 Tahoe 4 dr. 5.7 vortec. auto 4wd with 4 buttons, NP8, new process 246 W/272 ratio, asem#15037351 sr# 06-2399A, last 8 of the vin are XJ526530 All stock no mods just a after market car stereo that we know of. I think thats all the info needed right? let me know if i missed anything. and thanks in advance for any help !!

My brother owns this Tahoe but its me that gets to figure it out and fix it. Here's the deal, he first noticed it seemed to have no reverse leaveing a parking lot but was able to drive out foward and no problems except he now says he had heard some slight whirling noise maybe like a serp belt bearing he said but olny in 1st gear at low rpm once it went to second the noise went away. and it did'nt always do it. then not being able to back up. no atention was paid to lights on the dash or anything like that.{ keep in mind my bro is kind of a its got gas & oil & tires and him in it it should go guy!}

So in my heated garage a buddy of mine checks it out for me being a mech of many years, he says the Tcase is shot it had NO fluid in it at all. so i went with that no question. I got all the info did my home work and bought a quality used t case and installed it. Only to my surprise $400.00 and 8 hrs later I'm in no better shape then i was before. so now we start again, after i got it all in and spun the back tire only to hear the same noise as before. kind of like when your still moving and somebody slams it in park noise kinda grinding but not i guess. end result the truck is basicaly in nuetral, next i check the t case fuse its blown replaced it noticed a faint spark as i put it in, then i hear things under the dash powering up. ok now turning key on I note the 2hi and auto 4wd button lights are both on. I cant start it cause the bat went down while i did the t case prolly left the hood up light on thing . car on the ground now batt charged i note the fuse is again blown. same thing happens new fuse, spark, motors run with the key off. key on lights both on i start it and no reverse same sound like before, i go on to drive and it goes in gear like normal then quickly into park so as not to hear the stripped gear noise i'll call it. and fuse is blown lights both on. so i pull the 4x4 switch pannel put new fuse in and same events follow with the 4x4 switch un pluged. I'm not sure when exactly it blows but thats where i sit now.
I tried to not make this a novel but reading your forum for a week or so now i just wanted to give all the info up front and hope one of you guys tell me something other than "Its the freaking trany you Idiot"
So, I can take it (i think it) who's gonna pop my bubble today LOL
AGAIN THANKS
breazin

 

[96ProCompTahoe]

and you have no check engine light at all?

 

[breazin]

yes its been on due to engine miss fire # 6 wire we found to have a hole in it. the guy that originaly told me t case was shot. pulled codes but didnt have the right scanner to read all the codes he said. And i havent found anybody that does as of yet. Is that what i need next to properly figure out the problem?

 

[96ProCompTahoe]

it may help you pinpoint it better. whats the trans fluid look like? clean or black and burnt smelling?

before i had my trans rebuilt it wouldn't shift into reverse 75% of the time, would have to sit and play with the shifter to get it to click in. 1-2 shift was a little slow, but not really noticable if you werent looking for it. it wasn't a "complete" failure, but needed rebuilt. had a buddy rebuild it with much better parts.

have you made sure there aren't any pinched wires going to the T-case? if it keeps blowing the fuse id say you have a short in it somewhere.

 

[breazin]

from what i understand the scanner to do the trany info and abs is a $7000.00 unit so i dont see that happening in my garage anyways. the trans fluid looked good and didnt smell burnt at all. Having just replaced the t case myself all wires in that area seemed good but i'll re check them and i guess i will un plug the motor on the front diff and t case too i guess to rule them out as the short??

 

[SunlitComet]

I am up for some bubble burstiing.

As far as the tranny is concerned you may have broken the sunshell inside. There are transmision codes as part of the basic OBD2 but a broken sunshell might not pop one out.

The t-case: What fuse are you talking about exactly?

A tranny shop should have the scanner with the prope interface software modules.

And you don't have to spend seven grand.

You can actually get a gm scanner for $1700 off ebay and there are plenty of them.

A no dealer one that does tSpecial tranny, abs, airbag etc start at about $500 for a hanheld or $350 for a lap/desktop based unit.

---------- Post added at 04:39 PM ---------- Previous post was at 04:27 PM ----------

A history should be stored in the various control modules

 

[breazin]

Its the #2 fuse on the left side of the dash. I have saved and printed some of your other reply's telling how to jumper the scanner connection and read the lights as they flash and get codes that way can i use that method since i cant afford a scanner nor do i want to push it outta the warm garage its in and take a chance on doing more damage driving it to a shop? probably grasping at strings here but a trany overhaul is more than we can afford for real too.
thanks for your help

Breazin

 

[SunlitComet]

Actually the auto 4wd require a scanner I don't think you can use the other method like the non autos. But there is just more physical testing to do to narrow it down. So far it sounds like like your t-case control module relays are jammed or your shift motor has failed internally( probably the brake clutch causing the sfift shaft to get stuck and the motor fighting the brake and drawing to much current).

Can you say when you transfered the case was fuse blowing before and how about if the shift motor was reused from the original case.

 

[breazin]

Funny you mention the brake pedal in that mix. having little time in the truck as it belongs to my brother. I remember after the t case r&r and before as well with the enginge running we noted the no reverse problem and noise like hitting park before fully stopped, so i just turned the key off figuring I could put it park w/o hurting anything ya know. But it wouldnt turn off the engine, key almost to the full off pos. foot on brake (on brake the whole time)gear selector in nuetral engine still running like the key was on. I went to shift my body and let off the brake for a sec and then the thing just cut off like it shoulda when i turned the key off. so i put it in park and start it again foot on brake in park i let off the brake and nothing the 4x4 lights were still same as before auto and 2hi lit. so quickly i pulled the gear shifter in to nuetral and turned off the key same as before nothing foot off brake now it s shuts off as if i just turned the key off then. So how is the brake pedal involved in this deal why wouold it run with the key off and then when i let off the brake the thing shuts off freaky if ya ask me .Oh too answer your Q i'm guessing the tcase fuse#2 was blown from the very begining. once i found it blown and replaced it i'd guess it blows when either the trany is shifted out of park or when i tried hitting the 2hi button i'm not really sure i know its not on contact putting it in or starting it up beyond that i'm guessing best guess is its ok till i try shifting anything manual or eletric. basickly changing the tcase had no effect on anything as far as i can recall a very poor original diag was made with little info or research before or durring diagnoisis. the tcase i put in was damn near a twin to what i took out even the assem # was really close to the same. so no motors controlers or anything have been tested changed swaped or thought about yet. ok you havent popped me bubble yet and i'm still hopefull ya wont have too lol hope i'm giving you the info ya need without going into more detail or babble then needed

thanks
Breazin

 

[SunlitComet]

I was not actually refering to the vehicle brake but to the shift motor brake on the transfer case. But since more ifo has come up please try a few things for me if you are up to it. Disconnect entirely the shift motor on the tcase it will have two connectors. Does the fuse still blow? Ensure the ignition switch feels solid without loosness or noise with good solid idents for each mode selection. If the engine continues it problems as you described while everything else seems to be fine I would seriously look at some wiring harness damage somewhere between the the left fender well to the end of the harness that reaches to the transfer case. It is still likely that there are all seperate problems. But let me now what happens when you check the other things I mentioned.

 

[breazin]

I have no choice but to be up for it at least till it goes beyond my ability to to fix this thing! another fine mess my mouth got me into ya know...lol ok I will check thoes thing wednessday and get back with ya. Damn you should start a tech line you could make good money i bet and still be a great help to many here as it seems you do a great thing here for a great many people. I'm sure myself and others send our many thanks for guys like yourself who give the time and help that i'm sure you spend for us. its not enough but Thanks Very Much Sunlitcomit!!!!

not sure but i gotta ask. ok the break thing i think its really more related to the whole problem rather than a seperate problem. see when i have it in fwd gear running foot on the break and let off the break no problem the wheels turn adn all is well. only when i have it in nuetral does it then finaly let the key turn the car off it seems ya know i'm not sure when i had it in fwd gear or D that i tried turning the key off then. i bet i only tried that when in nuetral so i know there is some saftey features in there is the break pedal and the ign connected in some way that its just close enough {the key } to the off possition whe i release the bk pedal that it goes that tiny bit more and shuts the truck off finaly? i know that reaching again but i had to ask anyway. thanks again sunlitcomit!!

 

[SunlitComet]

I wish I could make some money by doing it but I don't do for money. Although it would be nice so I have money for parts on mine to get it drivable again.

It still could be one big problem but it is more effective troubleshooting to test one thing at a time and then merge the results. It allows me to be objective towards the problems I ill look into the diagrams more in the next 24-48 hours and see If I can't find some something common between all of them.