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    Transmission fluid change? Should I? '93 GMC Sierra

    I've been searching and reading post after post on this subject and I'm still confused as to what I should do.

    My truck is a high mileage truck with a healthy 211,000 miles on it, I just bought it and know nothing of the history but the thing runs like a top so I'm assuming it must have been at least somewhat looked after

    Anyway a friend of mine wants to borrow the truck to move some furniture which is fine so I make sure I check all the fluids before he takes it this weekend. Everything looks good but when I pull the trans stick I notice the level is fine but the ATF is pretty brown and smells burnt. I've checked it before but it's usually been at night and I simply looked at the level not the color.

    The truck still drives great, shifts great, not a problem with anything, but this has me worried. I don't tow much of any loads but when I bought the truck it came with a hidden hitch and a 5th wheel in the back so it's fairly safe to assume it's pulled a few trailers in its day.


    So what's a guy to do? I've ruled out getting it flushed after reading this forum, but I'm wondering about trying to change the filter and fluid and doing it the way I've heard a few people suggest and disconnect one of the stock oil cooler lines and drain a bit... fill it up... drain a bit... fill it up.. until it comes out bright red. But, every once and awhile I read posts about people saying if it's brown just leave it alone because the particles in the fluid are helping it shift and taking them away it'll likely start to slip.




    So, given these facts

    1) Runs and shifts great
    2) Fluid is brown and smells burt
    3) I Don't haul big loads often, but plans for summer included maybe cement and also the boat for a fishing trip
    4) I know nothing about the history, if it's original... rebuilt... maintained...


    Therefor should I

    A) Leave it?
    B) Change just the fluid using oil cooler line?
    C) Drop the pan change filter/seal/fluid and check for filings?

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    All the particles will do it wear it more.
    If you flush it being that high of mileage you could very well start a leak.
    I would change the fluid, and filter. If it's burnt or brown it's not good.
    Just so you know you may develope a leak.
    I have never had a problem, I have never had a tranny flushed or done the fill, pump, fill thing. I just pull the pan, change filter, and put back together. It wouldn't hurt to change it again, by 30,000 or so if not before to help clean it out somemore.
    I would drop the pan, change the filter, and do it again within the year.


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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    That was my original plan of attack, if it wasn't for me "studying" up on the topic I would've just done exactly that.

    Do you think I should tell my buddy not to borrow the truck until I get the fluid changed? He's hauling just some couches etc so nothing heavy but it'll be going probably 250 miles round trip. I don't think it'll make things any worse since odds are I've been driving it like this for months but you never know.

    Would it be better if he drove it in D instead of OD? I think the company he works for is picking up the tab for fuel anyway.

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    I have seen fluid like that before, and done services on those tranys. just to have the highly detergented ATF take out the remainders of the seals, bands, clutches etc. rendering the truck immobile.

    Drove in to the shop under its own power, got towed away.
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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    that happened to me check mine and it was brown and burnt and changed the fluid and it started slipping,then only got 2 days out of it then had to put another tranny in it

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    2 fairly serious votes for "Leave it"

    Anymore input?

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    Wouldn't hurt.
    I you feel that it will start leaking and fall apart, don't, but start saving for a new one or a rebuild.
    Look on the bright side, if you replace/rebuild it you can have a stronger tranny.
    Just take care of that one.


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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    I figured pictures might help show what I'm dealing with. The lighting was poor so likely it'll appear darker then it really is but you can see it's definatly not red... I wish I had some ATF kicking around for a side by side






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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    for me personally I would change the fluid and filter but it all comes down to your decision. you could look at it as "if it aint broke dont fix it" method.

    good luck

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    Well.. my engine isn't broke and I still change out dirty oil in it as preventitive maintenance :)

    I'm just not a tranny guy! When I see dirty fluid I change the filter and change the fluid, that's what seems natural in my mind. But it seems so many people have experience with the tranny taking a crap right after the change so I'm at a loss with what to do

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    You don't need a side by side for that. It looks like really thin engine oil. Even if that's a little dark, it's bad.
    The reason people have problems, (I have changed fluid/filter, when burnt and been fine) is that if the seals and so forth are bad, the slude/(*&^ can "hold" it toghether. When you put new fluid in it, the detergents break that down, and parts can start to slip/leak.
    It's all up to you though.


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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    I'm in sort of the same situation but with 68k. I have a tech friend at a Chevy dealer here who says to change it all but I'm afraid the tranny will go away. He says they use an additive to prevent the detergent from eating the seals but I'm still not sure about it. Has anyone heard of this additive?
    Last edited by TWODOGGZ; 02-07-2008 at 07:09 PM.
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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    I cant believe I'm hearing this! Man, if sludge is what's holding your tranny together then you have more problems than fluid quality and are no matter what only temporarily and short term delaying the inevitable. A little service goes a long way, ESPECIALLY with Automatics. On a transmission dependant on certain hydraulic pressures in certain passageways at certain times cleanliness is the only way to go, the same rules go into overhauling, you have to be meticulously spotless as dirt/sludge will lead to improper operation no matter what. If seals need changed then change them. Flush it, use good quality, clean ATF (sythetic or semi syn even better) and add a full bottle of Lucas Transmission Additive. Leaving old broken down fluid in there will only compound the wear of anything that may be worn, all it's lubricating additives are worn out, it's suspension additives full of dirt accumulating over time and can no longer suspend new particles, the list goes on. The red in the fluid is dye, which does break down with time and does not mean the fluid is beyond its useful service life, but if it smells burnt by all means change it. Same for the filter it could be half plugged, lowering hydraulic pressures leading to excess clutch slippage and soon after completely burnt out clutches. I highly recommend following a service schedule of fluid/filter and band adjustment every 50,000 miles

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    after thinking about it some more, and you say it shifts fine and everything, do it. Most of the above replies are worst case scenario. If it was looked after like you think it was, you will probably be fine.

    If it does break, better to find out now, then when your friend has it loaded with furniture goin down the freeway.
    Last edited by DoMeStIc_FaN; 02-07-2008 at 09:15 PM.
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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    I agree. If the only thing holding your transmission together is crud, you are living on borrowed time. It's only a matter of time before, even with "doing nothing", the trans will fail.

    When I worked for NAPA, one of our customers was a used car lot. Their mechanic would buy K&W Trans-X by the case. He put it in almost every automatic transmission on the lot. He didn't even drain the fluid, or change the filters (on most). He used a suction gun down the fill tube & added either a pint or quart (depending on the severity of slippage, leakage, or rough shifting).

    He told me that "if Trans-X doesn't fix it, then they would slap a used trans from the junkyard in it"...even then, the Trans-X went into the junkyard transmission.

    I started using it in some of my old junk & discovered that it worked great (although I would change the fluid & filter at the same time). It seals minor leaks & improves shifts. So far, it's never made a transmission fail on me.
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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    Leave it alone escpecially if you don't know the service history. Just throw a bottle of Lucas Trans in it. If you do decide to change the oil and filter then put TWO bottles of Lucas trans in it.
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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    I think we're up to something like (6) for change it, (2) for leave it, and one jumped the fence from leave it to change it


    And I agree with the last few posts, if it is sludge that's holding my tranny together then to hell with it it's better I know about it close to home opposed to when I'm out traveling some back road in the middle of winter at -40C

    So next time I'm in the city I'll pick up a filter and seal and a bunch of ATF and make the change hopefully sooner then later. Which way would likely be the best for me since we know the ATF in there is crap if I drain the pan there still is quite alot of the burt junk in the torque converter, besides pulling the tranny out is the only other option the stock oil cooling line?

    Basically what's the best method going to get the most of the old junk out, and the new stuff in?
    Last edited by Big Tom; 02-08-2008 at 07:11 AM.

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    I vote for the change, but of course, it's your money! If it dies, it probably would have soon anyway, and unlike the used car dealer, you are concerned for the long haul.

    Personally, I would just drop the pan and change the filter, then do it again next time I changed the oil.

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    What others are saying are true. In my experience i've done tranny flushes with the oil looking like that or worse...even with particles in it and the vehicle ran better than ever with smoother/quicker shifts. I was afraid to change my tranny oil n filter at 67,000 MI. My fluid was slightly darkened so i was nervous. But it shifts smoother and quicker now. so it's all up to you. I'd go for it. :aniteef:
    Last edited by Triagewar; 02-08-2008 at 10:35 AM.

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    Re: Transmission fluid change? Should I? '93 GMC Sierra

    Quote Originally Posted by MrBSS
    I vote for the change, but of course, it's your money! If it dies, it probably would have soon anyway, and unlike the used car dealer, you are concerned for the long haul.

    Personally, I would just drop the pan and change the filter, then do it again next time I changed the oil.

    I only paid $1000 for the truck anyway so even if the tranny goes and I have to replace it I think I'm still money ahead Person I bought it from the oil pressure needle was bouncing around and so they thought the engine was shot, turns out it was the $8 seal on the oil filter adaptor and the engine was puking out oil and couldn't build up the pressure!

    So yeah, I guess I'll let my friend borrow the truck but when he's in the city I'll get him to pick up all the parts/fluid I need to get the job done. And I'll likely do what's been suggested and drop the pan now, then again the next oil change and then the fluid should be pretty good hopefully





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