Question about 1995 GMC Sierra

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Front seal on tranny blows

I just rebuilt my tranny and everything works great for about the first mile, afterwards, the thing builds up pressure and the front seal blows. This has happened before and the cooler lines were reversed, fixed that but it is still doing it. Any thoughts?

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Was the convertor lip scored? If so it will blow the seal easily

Posted on May 25, 2009


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1996 F350 4x4 7.5l Shifts fine when cold. After 30-40 miles tranny sticks in 1st gear while accelarating from stop and will rev to 4500 RPM before slamming into third gear. If you let it rev to approx....

Changing the fluild ( all of it) might fix it if your lucky. Something overheating sounds possible. Any cooling system problem can cause this and cleaning the cooling system and flushing out the transmission cooler in the raditor may go a long way towards fixing your problem. dity raditor and or coolant will cause this problem. I you clean everything real good and then go and drive it and it goes longer but still does it your in for another rebuild. this time put in a new raditor to make sure the transmission lasted as long as it's supposed to. It's possible the throttle pressure was'nt set right and the trans upshifts too early and therefore the transmission gets too hot cause the engine is going too slow to make good transmission pressure and the slipping transmission overheats. again even after corrected it'll still do it as the transmission internal seals are adamaged by heat and it'll need to be rebuilt again.

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My E4od has blown the front seal out twice. was working normal and actually very good last time was at 35 mps on a dirt road, no towing or any thing just puff and you are walking.Was rebuilt 20k ago and...

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My 700r4 front pump seal was pushed out what causes this

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Nov 15, 2009 | 1985 Chevrolet K1500

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I think transmission went out of my 97 gmc safari just had transmission rebuilt a year ago the only thing is i still have reverse would there be anything else which would cause this?

As weird as it sounds, the oil level in an automatic transmission can cause a few weird things like this so maybe a seal wasn't put in correcly when they rebuilt and oil leaked out, causing bugs and whatnot since the tranny doesn't have enough oil to build the right pressure to operate completely. And if they rebuilt it though, they should've changed the clutch packs in the tranny, but it could happen that they forgot some, or installed wrong and they broke after a while or a host of other things, cause in some models there are 2 or 3 different clutch packs, one for reverse (but not on all models) one for the normal drive gears (gears 1 through 3) and another for the overdrive (4th). So if the clutchpack for the normal drive gears broke or is too worn out cause they forgot to change it, then it would shift in reverse since the reverse clutch pack is good, and not go into drive cause the driver packs are shot. Although I never did dismantle a safari transmission so i cannot garanty you have a seperate clutch pack for reverse or not, so ask a local mechanic that is used to working with those models if it is possible in this model or not before payin to get the tranny opened again. If it's impossible for the clutch packs to cause this and the fluid level is OK, then the problem is probably in the valve body solenoid pack, and in that case it's bad news for the tranny... valve bodies are muchos muchos money and so is the ammount the garage will charge to change it.

Jul 17, 2009 | 1997 GMC Safari

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Tranny slipping real bad

This is common on this model. I hate to say this but, its time for a complete tranny rebuild. you have a seal issue and, this can cause the fragile nature of the gear set up to be disrupted. this is normal ware considering the mileage on this mini van.. if your budget is tight, just by some tranny sealer for the time being or, shop around for a used tranny at your local junk yard.

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Tranny slips

Tranny slippage can be caused by several things (each contributes to a varying degree, if at all)

1. cold parts are smaller > > > don't seal properly
2. cold fluid is more viscous > > > don't flow properly
3. bad fluid can cause build-up > > > slow actuators & clog fluid passages
4. worn parts > > > don't seal properly

Result: low fluid pressure pressing on bands/clutches = slippage

The good news: as everything warms up, tolerances normalize, system leaks seal & fluid flows more readily creating enough pressure to keep bands/clutches from slipping excessively (normal operation)

As for the 4WD not engaging, I would be willing to bet the front differential actuator is frozen/stuck (assuming it has worked recently)

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Oil consumption

Bad valve seals
Worn valve guides
Pressurized crankcase (oil pan) due to a clogged PCV valve or breather system
Blow-by from worn piston rings

Bad valve seals: The valves are located in thecylinder head above the combustion chamber. Oil is pumped at 50 to 80 psi of pressure into the top of the head, lubricating the valve-train; the valveshave seals on them to stop the flow of oil down into the engine when the valve is open. If the seals fail, oil is allowed to flow down into the combustion chamber and is burned.
Worn valve guides: The valves are guided by a small cylindrical chamber called a valve guide. These guides wear over time causing eccentricity (or slop); the excess gap allows the flow of oil down the valve stem into the combustion chamber to be burned. What about the valve seal you say? Well, the gap is too great for the seal to stop the oil flow, so down it goes to be burned.
Pressurized crankcase due to clogged PCV or breather system:The car's engine is a giant pump, consequently it must breathe. The PCV (Positive Crankcase Ventilation) system does just this, allows the engine to exhaust the excess pressure build-up (which is a natural phenomenon of the internal combustion engine). Carbon build-up is a by-product of an engine and can build up in the PCV system, clogging the breathing passages. This in turn pressurizes the oil pan and pushes oil up into the fuel delivery system, where it is fed into the engine and burned.
Blow-by from worn piston rings: The pistons in your car's engine have seals around them in the form of rings. These rings do two things:
  1. Seal the combustion chamber so the precious power developed from the firing of the cylinder is not lost.
  2. Provide vital lubrication to the cylinder walls.
When the rings wear out, the pressure from combustion reverses down into the oil pan, pressurizing it and forcing oil into the valve covers, through the breather system, back into the fuel delivery system, and into the engine to be burned.
You may ask yourself, "What can I do to stop this from happening?" Keep your oil and filter changed every 3,000 miles and keep the air filters changed every 12,000 miles!! This will keep sludge and carbon buildup down to a minimum. Understand that you can't stop mechanical wear, but you can slow it down!

Jan 15, 2009 | 2000 Saturn SL

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