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Old 06-05-2011, 09:03 AM
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700R4. Sudden loss of 2nd and OD.

Hi all. Been gone for a while working on guitar amps, grandkids, etc...

It appears that the tranny in my truck is going out. (1984 GMC K1500 w/ a 305.) My son has been driving it and called me one day saying that it wouldn't shift out of first. He got it home and I drove it up the highway and was able to get it to shift into 3rd if I got it up to about 40mph, lifted off the throttle and got back on it. No OD though. Standard 2-4 band/servo/drum problem.

I had driven it two days earlier and it was shifting just fine. The transmission fluid was down a little, but couldn't really be called low and didn't smell burnt at all.

(sidebar. Am I the only one who worries about my transmission when driving past fresh hot asphalt? It smells very similar to burning ATF.)

When I dropped the pan, I was expecting to find at least some debris, friction material, metal, etc. There wasn't any to speak of. I took the old filter apart to see what it had caught and there wasn't much in there either. The last 700R4 I tore apart (many years ago) had toasted the 2-4 band and the pan was full of shredded and burnt friction material and metal. This one looked like it had just been a little too long between filter changes. One of my neighbors rebuilds automatics for a living, exclusively Fords, but he agreed that it didn't look like one of the bands had been toasted.

I'm going to try to take the servo out this week to see if a seal has gone out, but I don't look forward to that with the tranny in the truck. I'm hoping that's all it is, but that's not how my luck usually works.

I'm going to be building a newer tranny later this summer for the truck, but can't do it right now and would like to get this working again for the time-being even if it means really toasting the tranny. I've already purchased a corvette servo for whatever tranny I build.

So here's the question... If the servo seals aren't leaking, would it do any good to use the corvette servo and shim the pin slightly to get the band working? I just don't see the indications of a burnt band and this tranny isn't going to be used after the end of the summer anyway, but I need to get this one working.

The replacement will either be out of a 1991 3/4 ton suburban or a 1988 GMC S/15 Jimmy w/ a 4.3L. I know that the 88 will need more internal upgrades, but it's free and the other one will actually cost money.

Any suggestions would be appreciated.

Thanks,
Matt

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Old 06-05-2011, 09:20 AM
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with the servo properly installed... use a pry bar on the servo cover to push it in... if the cover goes in deeply 3/8 of an inch.. the band is worn out , or the drum is cupped from heat - wear.

You can try a longer servo pin. Shimming up the servo may not help if the band is worn and the pin can not reach the band strut to apply
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Old 06-05-2011, 10:01 AM
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Thanks Crosley.

So, a little JB Weld on the tip of the servo pin and I should be good to go, right?

I hate timing like this. I plan on replacing it anyway, but couldn't it have waited a couple of months?

Actually, I may weld-and-grind the one from the corvette servo, depending on the existing travel. It should be the stock length. (Watch mine already have the longest pin available in it. That would be about par for the course.)

Matt
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Old 06-08-2011, 03:57 PM
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I found a running tranny out of a 1993 S15 that's getting parted out next week. I'll just have to run a converter lockup circuit. It's not perfect and the shift points might be a little weird, but it's almost free.

Especially if I can leave with it before they notice.

Matt
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Old 06-08-2011, 04:28 PM
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Quote:
Originally Posted by morcey2
Especially if I can leave with it before they notice.

Matt
I was with you 100%... up until this point. You sure your karma can stand the hit?
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Old 06-09-2011, 09:12 AM
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Quote:
Originally Posted by cobalt327
I was with you 100%... up until this point. You sure your karma can stand the hit?
My karma's waiting for a transmission also. Unfortunately it needs a cast-iron powerglide with unobtainium steels, a frozen-jello bellhousing, and a 13.2-spline output shaft.

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Old 06-15-2011, 03:25 PM
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Next question.

The truck is a 1984 GMC K1500 and the donor is a 1992 or 1993 S10 blazer. No computer on the 1984 other than the electronic spark control piece. The TCC lockup can't possibly be controlled by that and it already has the vacuum switch and, I assume, the Normally Open pressure switches in the 3 & 4 spots in the valve body.

If that's the case, the only thing I'd need to change over to the new tranny for the lockup to work correctly would be the pressure switches? And maybe the solenoid? (new solenoid, since they're easy to find. Pressure switches, not so much.) Every wiring diagram I can find is lacking any mention of the transmission electrical connections.

Matt
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Old 06-16-2011, 01:55 AM
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What wiring Info do you need, Trans or Truck Harness to Trans wiring?
http://www.rowand.net/Shop/Tech/LockupTCCWiring.htm
http://www.hughesperformance.com/pdfs/HP700-R4.pdf
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Old 06-16-2011, 07:20 AM
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Quote:
Originally Posted by SSedan64
What wiring Info do you need, Trans or Truck Harness to Trans wiring?
http://www.rowand.net/Shop/Tech/LockupTCCWiring.htm
http://www.hughesperformance.com/pdfs/HP700-R4.pdf
I'm trying to find the wiring for the truck harness on the 1984, but those links are very helpful.

But now I have a larger problem. I drained the tranny through the dipstick/fill port and it had quite a bit of water in it. It was never run w/ water in it as the fluid in the torque converter was nice and clean, but the owner turned the transmission upside down to get the transfer case off so all that water flowed up into the internals.

So I guess I'll rebuild this one first.

Which means I need the garage cleaned out.

Which means I need a truck.

Which means I need a transmission.

Which means I need the garage cleaned out.

Lather
Rinse
Repeat



Matt
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Old 06-16-2011, 03:11 PM
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Where did the water come from? Rain?

AutoZone's site has Wiring & Vacuum diagrams, now have to register to use them.
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Old 06-17-2011, 09:31 AM
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Quote:
Originally Posted by SSedan64
Where did the water come from? Rain?

AutoZone's site has Wiring & Vacuum diagrams, now have to register to use them.
Rain and snow. The dipstick tube was out and it looks like water would have been directed to the open hole by the shape of the bellhousing. The tranny was pretty well covered, but we've had the wettest spring on record here with lots of heavy snow, so it somehow found it's way in.

I went through the wiring diagrams at Autozone.com and they don't show any transmission wiring for 700r4 or 4L60 equipped vehicles. They do show them for the 4L60E ones though.

My neighbor who, up until a year or so ago, made his living rebuilding transmissions said that he's seen trannies that were left out and filled up the pan with water run fine after just cleaning out the valve body really well. But he's also seen them get just out of the driveway before smoking stuff. The only thing he said I might need to replace is the 2-4 band since it would have been directly in contact w/ the water when it got turned over. The clutches are much harder for the water to get to according to him. As long as the friction material didn't get exposed to it, they should be fine. I guess the adhesive used is water-soluble?

I'm going to pull the valve body and pump tonight and see what the rest of it looks like on the inside. Maybe I'll be pleasantly surprised.

Matt
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Old 06-17-2011, 08:58 PM
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Guess it needs a rebuild....

Against my better judgement, I tore it apart, at least down to the output shaft lock ring. My lock ring pliers are hiding downstairs somewhere.

There is just a tiny bit of rust on the manual valve and the valve just inboard of that. There's some surface rust on the sun shell and reverse input drum. It wipes off with my hand and isn't on any of the bearing/friction surfaces. The bushings that I've seen so far look brand new. 2-4 band looks pretty good, but it's pretty obvious that it's absorbed lots o' water. There was also quite a bit of water on the reverse input friction plates, but the plates themselves look brand new. But they always look brand new.

I haven't torn the input drum apart yet. That'll wait until tomorrow.

So, stuff I know I need to upgrade:

Intermediate servo. (this one has the lightest-duty servo in it).
3-4 clutches.
lo-reverse steels and reverse input steels to turbolator ones.
Mild shift improver kit. (TransGo? truck/minor towing)
Beast Sun Shell (maybe).

4500 RPM 9.5" Torque converter.

And finally.....

If a TransGo kit is installed improperly and destroys the transmission, is it then known as a TransWent kit? (not a good joke. Yes, it's friday and I'm tired.)

Matt
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Old 06-18-2011, 12:21 AM
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Quote:
Originally Posted by morcey2
If a TransGo kit is installed improperly and destroys the transmission, is it then known as a TransWent kit? (not a good joke. Yes, it's friday and I'm tired.)

Matt
Either that, or a Trans No-Go kit *groan*. And yes, it is late...
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Old 06-19-2011, 10:51 PM
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Got it all the way apart, with the exception of the low-reverse springs and piston. The bushings all look brand new. The clutches all look brand new. The low-reverse friction plates are losing chunks of material. The sun shell is the only internal piece that has significant rust, but it's getting replaced anyway.

I'm not sure what rebuild kit to get since I'm on a budget. But, being on a budget, I don't want to have to do it over again. I've got to get a new separator plate due to some after-teardown damage. (I stepped on it and bent it.)

So here's what I need now:

Sun shell (beast).
Servo (Corvette).
Upgraded 3-4 clutch pack.
Rebuild kit. (frictions, seals, band, etc..)
turbolator steels for Low-reverse and Reverse input clutches.
Boost valve assembly.
Shift improver kit.
More sleep.
A clean garage (most of which happened on saturday. We took 4 flatbed loads to the dump.)
Valium.

The Reverse input drum band surface is not dished or scored at all.

The only thing I haven't pulled apart yet is the pump.

Matt
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