89 bonneville trans pan replacement advice please - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat
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1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 12-28-2002, 02:07 PM   #1
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Default 89 bonneville trans pan replacement advice please

I'm the proud owner of a 1989 Bonneville. Or I guess I was....but not too proud I suppose.... because I allowed it to become my 16 year old daughter'* primary vehicle. The deal was, the car is still mine, but to drive it, she is responsible for all maintenance, plates, etc. I'll insure it and she cares for it from there.

4000 miles past an oil change date she ran it so far out of coolant that it stopped moving. and she was MAD AT THE CAR because the "brakes stopped working"! (Where DID I go wrong?? I wasn't this dense about cars at her age! Ah, but I had a wrenchead big brother....)

Anyway, amazingly, thanks to Bonneville, the head survived. Turned out when the grill "disappeared", something came through it and damaged the radiator. New radiator, hoses, caps, etc, later...and its driving again.

about 8 weeks later it overheats again. she pulls over untli the light goes off, and drives it the rest of the way home....ok the story gets better...

she puts coolant in it and goes to drive it again!!! luckily it refuses to move (but confusingly so....)

Turns out water pump is shot from the first damage. Should've known that, oh well, trusted the mechanic who was trying to keep her bill low.....and the tranny fluid everywhere? hopefully just blew the pressure line when the guy replaced the hard lines with rubber hosing....

anyway, new water pump and more later, take it out of the garage, clean it up. chck for a puddle. Yep, its dripping trans fluid, and NOT from putting it in. Check every line. Can't see anything where it hsould be coming from.

Crawl under it. and there it is. A pretty little hole in the trans pan where she apparently was "hurrying it home so it wouldnt overheat again" and bahah'd it down our snowy country roads.

So....that brings me here... HELP!!!

What does it take to change the pan on this? Is it a simple change? or is this a valves and other goodies situation? and is it even worth changing? or has she cooked the tranny? (She spent 10 minutes trying to force it back into the driveway in first gear!!!! ARGH!!!)

THANK YOU bonneville for being such a tough car. You're an And I'm sorry for what i've put you through.

thanks to anyone who can help get this poor little car out of this mess....
AnnMarie Cross
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Old 01-02-2003, 07:19 PM   #2
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the trans pan is a pretty straight forward replacement. since you already have a hole in it, it wont be that messy. the filter does stick sometimes, just make sure that the flat spring steel plate doesnt get knocked out when you take the filter out. it just rides on the bolts there, the tension of it holds it in place. one thing you might want to do is add a bottle of lucus transmission additive to the fluid when you refill it. this stuff works great and we recommend it with every trans service we do.
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Old 01-02-2003, 09:55 PM   #3
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Grrr stupid AOL screwed up and I lost my post.

I will sumarize.

Agree with everyone else on replacing the pan and saying it is fairly easy.

Start off by putting 4-4.5 quarts in the tranny then run through all the gears a couple of times and let it reach operating temp. Keep adding till the level is into the crosshatches. My 89 has taken between 5 and 6.25 quarts when I have dropped the pan so it just depends.

If everything seems to still be working ok the go find a shop that does transmission flushes and get the tranny flushed out. Typicaly dropping the pan only removes 25-40% of the fluid in the transmission and a flush will remove a 100% of the fluid. The flush will also remove all the tiny metal particles that are too small to be caught by the filter(really a screen that is damn near worthless.)

I don't like the Lucas stuff at all. The stuff feels like just ordinary 80w90 gear oil and it just can't be good to put anything that thick in anything that requires normal motor oil or ATF. Just use a high quality conventional or synthetic fluid. I have seen some good results with the BG Automatic transmisson conditioner addative so that might be an option to look into.
1989 LE Bonne 122,000 miles
Custom Open Element filter system, Strut Tower Brace from 2nd gen bonne
Future Mods:
Light Up Pontiac symbol in grill, 16 wheels from newer Bonne/G, performance tires, performance ignition system, Upgraded brakes.
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Old 01-03-2003, 01:15 AM   #4
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aside: lucas oil additive apparently is just bright stock with no additive benefit, except giving the oil the ability to climb. well that'* great, but what do we have oil pumps for then?
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Old 01-04-2003, 12:45 PM   #5
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lucus makes a variety of different additives for truck and auto uses. the trans additve is made just for auto transmissions. it conditions the clutches to get rid of any glazing on them, it also cleans up the inside of the trans from any varnish that has built up over the years. it also makes it shift smoother. they make a power steering additive too. it gets rid of the so called morning sickness that plagued GM for years. BG is also a great product too. i religously use BG MOA in my oil with every change. a rep from BG came to our shop a few years ago with a sbc on a trailer. they only added mechanical lifters to the engine as its only mod. warmed it up and then took the oil pan off. started it and left it run for 10 mins with no pan on it. then we reved it to almost 6000 rpms. the only thing you could see was the blow-by from the bottom of the pistons. then we put the pan back on and started it again. it held 40 psi of oil pressure as it did before the no oil run and havd absolutely no knock or rattle at all. BG products can be picked up at just about any GM dealership parts dept. MOA runs about $8 a can
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