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transmission ??

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knucksk5

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i have a 1989 k5 with original 700r4. Now that its toast i have a another 700r4 from a 1990 4x4 pickup to swap out. Is there any thing i need to change or modify to do this?
 
It is a direct swap, nothing to be changed,(other than filter and fluid maybe) resist the urge to change the front seal, it is way to easy to screw that up and make things worse.
 
See, I'm the opposite, if I have access to a seal that is normally difficult to get to, I'm gonna change it for cheap insurance and peace of mind, knowing it's a new seal and shouldn't leak anytime in the near future.

That goes for BOTH seals, front pump seal on a trans AND the rear main on the engine. Most of my engines have high mileage anyways, so it was another good reason to get it changed before it started leaking.
 
4xcrazy said:
See, I'm the opposite, if I have access to a seal that is normally difficult to get to, I'm gonna change it for cheap insurance and peace of mind, knowing it's a new seal and shouldn't leak anytime in the near future.

That goes for BOTH seals, front pump seal on a trans AND the rear main on the engine. Most of my engines have high mileage anyways, so it was another good reason to get it changed before it started leaking.
Click to expand...

Normally I would agree with you on this and what you say makes for a strong argument but hear me out on this unique transmission.
The 700R4 uses an aluminum pump and a steel seal housing. These contract and expand at different rates and the flange on the pump face is not especially robust. It is hard to find a tool that can get into that bellhousing and reach that seal without banging around on the seal edge or using one of those hook end seal extractors that can gouge the seal to pump interface surface.

Once you have the seal out of the pump, you may notice a ring of paint left where the seal used to be, this is the original bond holding these two together and you will need to remove this paint before the new seal is installed. Ideally, when installing a seal into an aluminum pump you will want to knurl both the seal area and the seal itself
and apply a light coating of red Loctite. This will reproduce that original bond and help keep that seal in place when the trans heats up and that aluminum starts to expand.

The original seal in its original bore had an advantage there. The original seal in an 89-91 trans also had a Viton double lip sealing surface which is an exceptional seal in terms of longevity, heat resistance and sealing ability. What is your parts store seal? The original seal when installed , or those installed by a professional, use a flanged tool to install the seal so it is uniformly inserted into the bore. The tool also holds the spring in place behind the seal apron so it doesn't pop off during installation. The DIY guy or shade tree will usually use a hammer, going side to side around that clumsy stator shaft, or maybe even a piece of pipe, distorting the seal flange and compromising the sealing surface. So what you end up with is a questionable repair in a pump known to be prone to spitting seals out.

And that little tin shield Hydramatic clipped on to "prevent seal blowout"? You can usually pop that off with your fingers, that will never hold 300psi of fluid rushing past a worn pump bushing and trying to find it's way back to the pan, it cannot be re-used so throw that away so it doesn't fall off after your install and gall the converter.

Sorry for the long explanation but in this instance on this trans if the seal isn't leaking, leave it alone.:D
 
I've seen more than one used 700R4 that had the bushing the torque converter snout rides on come out,stuck to the converter snout,when someone went to change the seal--and all attempts to retain a new one in the pump housing failed when locktite or J-B weld was tried...
So I agree with Greg,if its not leaking,I'd take the gamble the oem seal is OK and just install the transmission..normally I'd be mr.perfectionist too,and want to replace the seal and rear main while it was apart,but sometimes being too fussy leads to more problems..not prevent them..
 
Greg Ducato said:
Normally I would agree with you on this... <snip>

...Sorry for the long explanation but in this instance on this trans if the seal isn't leaking, leave it alone.:D
Click to expand...

When it comes to transmissions, if the honorable Mr. Ducato speaks up...I listen. Just sayin'. :waytogo:
 
The way to change the seal is to buy a remanufactured pump, from a reputable shop.
 
I agree with greg. Don't mess with it if it's not leaking. Me and a buddy made that mistake. We never got it right.

Edit. Greg is that what you do for a living?
 
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