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Small Crack is not a BIG problem: Transmission fixed!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blue85b, Mar 17, 2001.

  1. Blue85b

    Blue85b Registered Member

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    Yesterday the ride wouldn't shift into 2nd gear, soon after, it was slipping out of first. I thought that it was low on fluid, so I figured that since the day before I had the servo cover off, I didn't get the snap ring on right and I blew the servo cover off and dumped the fluid. So I got it to a place I could leave it for a while and looked underneath. Sure enough, snap ring half off and cover crooked with fluid everywhere. But I thought it was no big deal, that I could just put it back together after work and be done.
    However, when I went back and looked at it later, I think my face literally went pale. The transmission case itself has a crack in it right outside where the snap ring groove is for the servo. So I have to either get a new case (i.e. tear out and rebuild), get a new transmission, or see if somebody can weld it for me. I am going for the third option since it is the least work and allows me to save all of the high performance parts that I just put into this slushbox. Can this be done? What kind of shop should I look for? Do you think they can do it with the tranny in the truck, just with the whole servo removed?

    But why did this happen? Did the increased force due to my Corvette Servo upgrades cause the cracking in the case there? I have been having some trouble since that upgrade gettting the thing to drop into OD. It's been intermittent. The change I did two days ago was to replace the seal on the 4th apply piston, because I feared it was letting oil leak past, causing my OD problem. Is this my fault or a freak occurance?

    Thanks for any help
     
  2. ftn96

    ftn96 1/2 ton status

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    Re: Small Crack, Big Problem, tranny guys Please Help

    Well, I had the same thing happen to a 700 I built a while back. The cases are aluminum. Im no welder but I think aluminum can be welded but I seem to remember some negatives involved. Seems like the best thing would be to find a replacement tranny and just swap them out.

    Will work for beer, parts and tools.
    90 Jimmy 350TBI-700R4-241-33" BFGs-10 bolts w/4.10's
    <A target="_blank" HREF=http://www.nashvillek5.freeservers.com>http://www.nashvillek5.freeservers.com</A>
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Small Crack, Big Problem, tranny guys Please Help

    Well I'm no tranny guru, but I've welded a lot of aluminum...
    First of all cast aluminum is a bitch to weld, secondly it has to be deadly clean. Even if the entire tranny was dis-assembled and cleaned it would be a tricky fix depending on where and how its cracked. The heat of the welding causes a lot of distortion in the material, but cast aluminum is very rigid, this can lead to even more cracking...

    I would suggest a new case.

    Rene

    [​IMG]<A target="_blank" HREF=http://jules.coloradok5.com>http://jules.coloradok5.com</A>
     
  4. Blue85b

    Blue85b Registered Member

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    Re: Small Crack, BIGGER problems. I need help!

    OK, things have gotten much worse.

    I patched the tranny back together and drove it home. It was leaking fluid out of the servo cover because the seal got cut, but it was driving and using 3 gears, at least (I never went fast enough to even try OD). It turns out that the cover/snap ring had just been on wrong. So today I took it out to see if 4th gear would work now that it is put together "right".

    Well, there was no OD, but there was some smoke, so I turned around to go back home. When I stopped, fluid started dumping out of the dipstick tube and igniting on the manifold, so I had a nice engine fire and lost about 3 wires and a few vacuum lines. It would have been a lot worse, but I happened to have a 2-liter of pop, which I never knew could be such a lifesaver.

    Now I am really bummed. What is wrong with my tranny? Why doesn't OD work? Why does it shoot fluid out? Is the fluid unhappy with its home? I have an auxillary cooler and after the fire was doused, I could still put my hand on the tranny oil pan.

    I'm getting it towed to a tranny shop tomorrow. I don't have time to deal with this. Please share any experience that you have because I need help.
     
  5. Wheels

    Wheels 1/2 ton status

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    Re: Small Crack, BIGGER problems. I need help!

    There are two different types of 700R4 cases (besides the obvious 82 - 87 and 88 to 93 models). One has the 4 bolt dust shield (flywheel cover) and the other has a 6 bolt dust shield. The latter is supposed to be the stronger of the two cases. I was warned of this earlier and in doing my 700R4 swap, I found a 6 bolt dust shield. If yours is cracked, Rene has a good point in trying to get it welded. Welding may cause the case to become brittle in the weld area and about the first time you romp on it, it may just let loose again. My .05.
     
  6. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: Small Crack, BIGGER problems. I need help!

    It sounds like you overheated the heck outta the tranny... so basically I think you're kinda SOL on this one.... sorry. Probably would be easier just to get another tranny and throw it in. A live and learn experience... I learned when I was 16 and a buddy tried doing a shift kit... he screwed it up and blew out his tranny. I still won't do anymore then a shift kit LOL... Funny thing is now that buddy is a tranny shop tech. It pisted him off so he wanted to learn. haha Good luck with the tranny... I think we have all been there before.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  7. Blue85b

    Blue85b Registered Member

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    Re: Small Crack, BIGGER problems. I need help!

    If it's overheating so bad, why isn't the case more than just warm? Is it just some kind of localized heating, like in one of the clutches or something that heats enough air in the case to shoot fluid out, but doesn't have enough time to heat the whole tranny?

    I'm sorry, but I'm not doing anything that a good 700 shouldn't last 80,000 miles at. If I have to replace the transmission once a year, I'm just not gonna deal with it.
     
  8. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: Small Crack, BIGGER problems. I need help!

    I can't say exactly on why the pan was only warm or what not... I've never stopped and felt the pan when fluid is gushing out the vent or dipstick tube. About 95% of the time I have found that means either there is too much fluid in it, it is overheating, or has a big clog in the tranny. A properly built 700R4 should hold up to your needs. My buddy built one for one of my street/strip cars pushing 425 horses and he is experimenting w/ one behind his 500 hp big block as we speak. But really sounds like the problem is something got messed up when you had the servo cover off and what not. Unfortunetly I think the tranny shop is gonna say time for a new one... or a rebuilt and eat the core charge. Just to let you know bad 700 rebuilds happen... my truck had a rebuilt 700R4 in it approx. 40 k before I bought it and it blew up... literally... My bud dropped the pan said it look like the dang near everything was in the pan... valves, regulator, piece of bands even... yuck.

    [​IMG]
    1987 Chevy K5 Blazer- 350 TBI
     
  9. muddin4fun

    muddin4fun 3/4 ton status

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    Re: Small Crack, BIGGER problems. I need help!

    I don't know if you're running big tires or not, but my experiance with 700's is that unless you dump a lot of money into heavy duty parts for it, they're just not a good heavy duty tranny. They are very sensitivy to heat and high rpm from what I have experianced and heard. A good tranny cooler is a must for any auto tranny and a good investment. Just my .02.

    [​IMG]


    <A target="_blank" HREF=http://muddin4fun.coloradok5.com>http://muddin4fun.coloradok5.com</A>
     
  10. Blue85

    Blue85 Troll Premium Member

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    Re: Small Crack, BIGGER problems. I need help!

    I have a big cooler. It's the kind made for a motor home. It's possible that I just overfilled it. I picked up a new B&M temp gauge today and I plan to get a new dipstick and clean out my vent before trying to move the vehicle again. It turns out that there was a recall on these tranny dipsticks and at one point dealers were replacing them all with the sealing kind that has the locking top. I won't drive it again until I can ensure that I won't have anther fire. I got it to run again this morning, but no tranny shop seemed to have a clue as to what to look for, other than "well, we'll road test it..." so I didn't have it towed anywhere. I'll probably run some tubing from the vent down around so that if she decides to burb fluid, it'll hit the asphalt and not a hot exhaust. I'm also gonna drop the pan to look for stuff and change the filter and check out the old one. All of the fluid coming out of her is bright red and smells like it just came out of the bottle.

    Maybe I should just buy a 3/4 ton 4x4, with a TH350, NP205, 14B and dana 44 w/4.11's and just swap everything at once and give up on OD. What do you think? Anybody got one for sale?

    I'm kind of afraid to go for a rebuild because everybody seems to have a ton of trouble with them. At least I got half a year out of the one I did myself. And I probably would have gotten more if I hadn't been messing with the servo so much...

    <font color=green>Stupid tourist at Mammoth Cave, Kentucky: "How many miles of unexplored passages are there?"</font color=green>
     
  11. Blue85

    Blue85 Troll Premium Member

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    Re: Small Crack, BIGGER problems. I need help!

    BTW, I DID dump money into it just this last summer. I did a B&M Super TransKit (seals, high-perf frictions, upgraded 3-4 clutch pack, 2-1 downshift valve, high pressure pump upgrade, shift recalibrations, accumulator modifications, etc.) ($250), a new torque converter ($110), an 88 oil pump (10-vane instead of 7-vane, plus better rings) ($50?), upgraded sprags ($40?), etc. It was because of all of the shift recalibrations that I needed the Corvette Servo and I got into all of this trouble to begin with.

    <font color=red>Stupid tourist at Mammoth Cave, Kentucky: "Will it hurt anything if I take a picture of complete darkness?"</font color=red>
     
  12. Blue85

    Blue85 Troll Premium Member

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    Re: Small Crack, BIGGER problems. I need help!

    Well, I am still not convinced that I am screwed.

    I've now driven the truck a few miles without any incidents. I dropped the pan, found a little "sand", tiny amounts of metal "sparkles" and almost no build up on the bottom of the pan. I fixed the leaking servo cover, removed a small piece of something from my vent tube and installed a locking dipstick (these are only $6 from the dealer - well worth it for piece of mind.) I put in a new filter, filled it back up and away I went. It worked fine, but I didn't have the guts to try the overdrive.

    I've had lengthy conversations with the guys at B&M over the last two days and based on what I've seen, they don't think that there is too much wrong with the transmission and that there is not much risk in driving it. My next step will be to take out the Corvette parts and put the stock 2nd apply piston back in the servo. If that fixes it, I'll just have to live with the 2-3 flare up (i.e. always get off the gas for that shift) or make some changes to the valve body to make it work with a stock servo. If that doesn't fix it, then I'll try a new Servo cover and 4th apply piston. After that, the valve body will be cleaned and the governor checked out. If there is still no overdrive I will have to pull the tranny (could be the sprag that rotates for the shift in and out of OD, they're infamous on 700's) or keep it in 3rd from now on and pretend that it is a TH350.

    <font color=green>Stupid tourist at Mammoth Cave, Kentucky: "How many miles of unexplored passages are there?"</font color=green>
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Small Crack, BIGGER problems. I need help!

    Ok, I'm picturing the case in my mind..if the crack has extended into the servo area, (the actual servo bore)you are likely going to have pressure leaks from the inside out. However, the worst that can happen driving it is that it finally fails. The best is that it works fine, and you never worry about it again.

    Friend put a Corvette servo in his dads truck, and somehow he didn't get the snap ring on right either. Blew it out about 300 ft down the road on the test drive. he was lucky, no crack or anything, but its amazing that the snap ring can appear to be seated correctly yet blow out.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  14. Blue85

    Blue85 Troll Premium Member

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    Re: Small Crack, BIGGER problems. I need help!

    The crack is actually a missing piece now. If you look at the servo bore in the case, there are two slots, 90 degrees apart, so that you can poke the snap ring out. I lost about 1/3-1/2 of the area between those slots. So there is no problem with the case further in than the snap ring groove. I actually think that it is going to be OK that way. The snap ring probably covers about 330 degrees when it is expanded and there is no procedure saying that it should be aligned a certain way with respect to the slots , so with the two slots, you probably have about 300 degrees of coverage, worst-case, with a good transmission case. I still have a little more than that right now, because I have the gap of the snap ring in the broken area of the case. The only difference is that in the original configuration spreads out the breaks into three locations instead of two, the way I have it now.

    I have driven it to work two days in a row now with no problems, but I still don't have any OD, even with the stock servo put back in and the TV cable readjusted. I am convinced that it is either the governor or a valve body problem, so I am confident now that I can get it back on track without pulling it out of the truck.

    There is slight damage to the Corvette servo parts. There is evidence that the 2nd apply piston housing cocked sideways on the 2nd apply piston at some point. It must have been when the servo cover came partway off. Scary stuff. Praise God that something a lot worse didn't happen.

    <font color=green>Stupid tourist at Mammoth Cave, Kentucky: "How many miles of unexplored passages are there?"</font color=green>
     
  15. Blue85b

    Blue85b Registered Member

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    Well, now I the old girl is working properly again. It turns out that the biggest problem with the overdrive was really that I had lost lockup. For a given cruising speed, there is more torque through the torque converter in 4th gear than in 3rd, so there is more slip. Because of this, the engine rpm was only about 100 rpm lower in 4th gear, so it gave the illusion that it was not shifting into overdrive. I traced the problem back to the lockp-up brake pedal switch under the dash. The contacts were kind of dirty and burned, so I just rebuilt the switch. Everything in the tranny is clean and working now. The 'Vette servo is in and all of my shifts are clean and firm. A while back I thought that I was looking at a new tranny or another rebuild, but God is just good.
     

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