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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Jon87V20 on February 01, 2017, 02:06:53 pm
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So I finally pulled my transmission over the weekend. To my surprise the bell-housing had a giant crack going through it (see attached photo), and my torque converter seemed to be broken as well (tons of play in it). I was able to find another Turbo 400 and I bought a new torque converter as well. When I was removing the transfer case, I found that the large stabilizer bar that runs from the transfer case to the bell-housing, was only connected on the transfer case side. Someone had removed and/or lost the bolts on the engine side. Could this have been a contributing factor in the transmission case cracking?
Does anyone have any tips for re-installing these, or things to watch out for? It took me months to save up to start putting the truck back together and I want to take all the precautions not to mess anything up as I can't afford to replace these again. It's been suggested to me that I should be sure to flush the transmission cooler before re-connecting it. Is there a way to do this at home in the garage on the cheap? I'm going to replace the engine's rear main seal while I'm in there as it appears to be the cause of a messy leak down there.
Is there any special procedure to installing the torque converter? Do I need to fill it first? How much? Does it need to be seated a certain way to prevent damaging it? Just really nervous about doing something wrong. Also, to make matters worse, I had to cut the exhaust out to get the tranny out, as it was a solid chunk of rust so it's going to be extremely loud when I test it. I won't be able to hear any noises. I'll probably have to wait to fire it up until I have the new exhaust in place I suppose.
When I pulled the rear slip-yoke out of the transfer case, I noticed a bit of fluid on the shaft. Is this normal, or does this indicate that I may need to replace a seal there?
A bombardment of questions here, but I thank you in advance for any advice!
'87 Chevy Suburban V20 350ci TH400 NP208
-Jonathan
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Are you talking about installing the braces? If so the go on last.
On the converter I put a couple quarts (enough that it can tilt and not bathe me) slide it in and with slight pressure turn it until it seats.
Chris Lucas
73-87chevytrucks.com
squarebody.biz
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Captain, I was talking about this stabilizer/brace that goes on the side of the t-case (see attached photo). Could not having this attached on both sides cause some kind of stress that could contribute to the transmission case cracking like that?
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Loose bellhousing bolts, bad mounts, excessive stress and the like can cause it. The support hooked up will certainly help prevent it from reoccurring but check your mounts too. You should have 3 engagements of the torque converter, the pump gear, the stator and the turbine. Install it when you are ready to install the transmission as so that it is not hanging on the seal. Lube it with ATF and fill it as Captkaos suggested. When installed you should be able to easily rotate the TC before fastening it to the flexplate. Do no fully tighten all of the bolts until all 3 are in. Use a little thread locker and tighten them fully only after you've tightened all bellhousing bolts. As far as your exhaust goes, just slip on a connector and some exhaust clamps to get you up and running.
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Ok thanks. Also, what do you call the gasket between the transmission and t-case where they bolt together?
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The transfer case to bellhousing brace is a good preventative measure. The intended function of that brace was to keep the bell from cracking. I wouldn't run her for long without one.
The brace bolt-up is shown in the below illustration as well as the gaskets. You can also see where they ran the transfer case vent to the rear of the engine... I ran all my axle, trans, and xfer-case vents up there.
All you need is a longer bellhousing bolt or stud for the bar. www.gmpartswiki.com/getpage?pageid=56919 (http://www.gmpartswiki.com/getpage?pageid=56919)
The TH400 is RPO M40.
(http://www.gmpartswiki.com/getbigpage?pageid=56919)(http://www.gmpartswiki.com/getbigpage?pageid=56927)
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Ok thanks. Also, what do you call the gasket between the transmission and t-case where they bolt together?
It's just called a gasket, no special name for it.
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You can use this to clean the cooler & lines.
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You can use this to clean the cooler & lines.
Oh nice! I've never seen that before. That definitely makes things easier.
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Ok thanks. Also, what do you call the gasket between the transmission and t-case where they bolt together?
It's just called a gasket, no special name for it.
If I have trouble tracking the gasket down at the store, is this something that I can RTV, or is that a bad idea?
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go oon ebay and search np208 gasket
http://www.ebay.com/sch/i.html?_odkw=th400+np208+gasket&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xnp208+gasket.TRS0&_nkw=np208+gasket&_sacat=0
me i would use rtv "right stuff"
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Anaerobic Sealer
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Anaerobic Sealer
Yup. I tell them that at work all the time. Nobody listens though.
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Loctite 518 (https://www.summitracing.com/parts/lct-2096059)
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This looks right, correct?
If so do I want to use sealant in conjunction with this, or leave it dry?
http://www.oreillyauto.com/site/c/detail/PIO0/749090/03236.oap?year=1987&make=Chevrolet&model=V20%2BSuburban%2B4WD&vi=5013090&ck=Search_transmission+gasket_C0071_5013090_3825&keyword=transmission+gasket&pt=C0071&ppt=C0338#itemDetailTab_
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this is what they norm look like
(http://i.ebayimg.com/images/g/Z40AAOSwrklVVtW~/s-l500.jpg)
that one you posted is different but it just might be cause its from a different maker. but if you look it covers the th400 and thats it. i think the 4l80e should be covered also or other trans like the 700r4
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Any thoughts on whether I should use sealant with this gasket, or leave it dry?
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i use sealant to hold it in place but only a few dabs
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Any thoughts on whether I should use sealant with this gasket, or leave it dry?
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Use one or the other. if you use a sealant then you don't need a gasket.
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If it were mine I would just use the anaerobic sealant.
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I use a little grease to hold fiber gaskets in place.
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Hey guys, ran in to another issue. I got the new TC and transmission up in the truck and bolted up to the engine. I noticed before bolting the TC up to the flexplate, it has a bit of play in it. It's able to move away from the flexplate just a little bit. I'm not sure if this is normal. Do I need to get some washers?
I found another thread on here:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=31235.msg262304#msg262304 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=31235.msg262304#msg262304)
where HAULIN' IT says it's normal for the TC to move a little bit, but if it's more than an 1/8", you should add hardened washers. I haven't measured it because I haven't been down there since I read that, but I have a picture of the gap. Just wondering what you guys think about the clearance here.
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No, the nose of the converter needs to be in the back of the crankshaft. The converter spins freely? If so just carefully draw it into the flexplate.
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Ok. So when the converter pads come in contact with the flexplate, the nose of the converter should be in the cutout on the flexplate and everything is good to go? Also, yes it does spin around freely. I just wanted to be sure so it didn't start breaking things when I fire it up.
Thanks, Vile!
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Just for future reference, the gasket I bought at the link was not the right one. Don't buy that one.
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Happy to report, I finished throwing her together today and drove it around the block. Seems like everything is operating properly, no leaks etc. The only issue I ran in to is it won't go in to park. When it's in park and it's rolling slightly, I can feel a slight "clicking" through the shift handle. I'm thinking this is probably a shift linkage issue (I hope!). Thanks to everyone for all the help! I wouldn't have been able to get this done with out the forum for sure.
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...The only issue I ran in to is it won't go in to park. When it's in park and it's rolling slightly, I can feel a slight "clicking" through the shift handle. I'm thinking this is probably a shift linkage issue (I hope!)....
Adjusting the linkage should remedy that, but don't put it off. If Park doesn't detent correctly, neither will the other gears, which could result in slippage and overheating or other problems.
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So I went out and made sure that the linkage was correct and even took the linkage off and moved the shift mechanism with my hand and it is snapping in to the park position. However, the truck is still moving. I've noticed that if I push the truck backwards, it makes no attempt to hold it still. I hear the light clicking but there's no resistance. If I pull the truck forward though, there's a little bit of resistance and I can see the engine move a bit. It will stop the truck from moving if it's BARELY moving, but I can pull a bit more with my arms and it will move a few inches until the next catch point.
I'm not familiar with how the park mechanism works inside the transmission. Is it some kind of pin that drops in to place somewhere in there, or does it engage two gears at once or something? This is a big disappointment as I don't have anymore money for this now. Everything else seems to be working okay though. I'm thinking since the parking brake works quite well on this truck, I'll avoid parking on any significant grades and keep a wheel chalk with me for now.
I may just eventually bring it to AAMCO or another transmission repair place and tell them it won't hold still in park.
Anything else I should try before I give up on getting it to hold still?
Thanks!
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After doing some more reading I'm feeling a lot more optimistic about this now. It seems as though you can access the parking pawl mechanism from the bottom after removing the pan. As soon as I have money to buy more fluid ::), I'll drain it and see what I find.
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It's beginning to sound like a fractured or dislodged parking pawl. See Figure 31, page 400-15 of the 1987 Unit Repair Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Unit_Repair/ST_333_87_1987_Chevrolet_Light_Duty_Truck_Unit_Repair_Manual.pdf#page=677). As you've already discovered, the pawl is easily serviceable after removing the pan. IMSM, the pawl engages the outer teeth of the output carrier assembly (item #675 in Figure 22, page 400-10 of the same repair manual). If the pawl is damaged, you maybe able to swap in the old one from the original THM 400 with the cracked bell housing.
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and get a clean receptacle to catch your fluid in. Use a filter screen or paper towel in the funnel when refilling it if money is tight.
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Thanks for that info from the manual, BD. Unfortunately, I already scrapped that old Tranny. I really wish I would've thought about taking that pawl out of there before. Oh well. I'm assuming I can probably order parts for that somewhere online.
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Local transmission shop or tranny parts retailer.