My car now has 268K miles and the engine is still running but my second transmission just died. I have located another trans from a 95 bonne with 76k miles and I also located a engine from a 96 bonne with 48K miles.
My questions are :
What would you replace on the trans before installing? (seals, gaskets, filters)?
What gaskets / parts would you replace on the engine before replacement? (upper intake/ lower intake), main seals)??
I have replace the front hub bearings, My rear hub bearings now have 268K .. would you replace them?
I also have the stock Cataletic converter ... Does it clog over time and need replaced?

Also, I believe they can be removed as one unit from above. Is that correct?

Yes the engine and trans can be removed together. Here is the procedure for a '95: http://www.bonnevilleclub.com/forum/...e=article&k=84

Here is a post describing how to prepare the tranny: http://www.bonnevilleclub.com/forum/...ic.php?t=29367

I would also strongly advise you to change the crankshaft rear seal on the engine before installing it or bolting it to the trans.

Here are my recommendations for UIM/LIM repairs for the 95-05 L36.

Please note that if you cannot wait for parts in the mail, you will not get the best fix.

The best fix for the LIM - GM aluminum frame gaskets......$59
The best fix for the coolant elbow(*) Dorman Help.........$6
The best fix for the UIM - APN upper intake manifold kit......$115 including shipping

In addition, I recommend the following steps to keep engine operating temperatures down, to ensure that coolant flows around the hot stovepipe area in the plastic UIM, and to eliminate any possible harm from the use of Dex-cool - all factors that protect and extend the life of the UIM and LIM gaskets.

Flush coolant and re-fill with "mixes with any color"
Drill a 1/16" hole in a 180F thermostat flange and refill according to: http://www.bonnevilleclub.com/forum/...=article&k=100
Install an after-market transmission cooler.

I use only a scraper and degreaser to clean gasket surfaces on the cylinder heads to avoid introducing abrasives into the engine.

Regarding the UIM, the longest-lasting fix will come from an upper intake manifold protected by a heat shield and the use of a reduced diameter stovepipe to provide an insulating gap between the hot stovepipe and the metal heat shield. The only commercially available kit that provides those features is from APN. Dorman UIMs have NO heat shield protection for the plastic EGR bore, but rely solely on the insulating gap provided by a reduced diameter stovepipe.

UIMs can be sleeved, plugged, and otherwise repaired for re-use, and these repairs can be made at low cost. But, unless the UIM is fairly new, most will typically exhibit warpage at the throttle body sealing surface and at the coolant passage sealing surfaces around the EGR bore. When considering repair of a UIM, don't forget to add the costs of a new UIM-LIM gasket and throttle body gasket, typically about $45.

From Sears, a smaller 3/8" drive deflecting beam type torque wrench does just fine for UIM/LIM work. It costs $25. http://www.sears.com/sr/javasr/produ...id=00944690000

Unlike the UIM/LIM that you want to do BEFORE you need to, I would wait to replace the cat and the rear bearings until they go bad.

Thanks for the reply, Does my car use the Dex-cool or the Yellow prestone stuff??

I seem to remember doing a flush / fill with the yellow stuff before?

Your car should have been shipped new with green coolant. GM started shipping most of its cars in 1996 with Dex-cool. But, since most members have not bought their cars new, it is not obvious whether a previous owner flushed and re-filled with the "newer- better" Dex-cool that turned out to be only newer, and by many assessments, much worse.

If you got the engine out, might as well replace ALL the gaskets now. I think I spent close to $100 for all new gaskets top to bottom. A wise investment if you would like a worry free, leak free engine. Same goes for the trans. Pull both pans off, flush it real good with cheap trans fluid(along with the TQ) then retop off with good trans oil. Don't forget to flush the trans cooler lines going to the radiator. Try to remove as much of the old fluid as possible.

Knowing you did it right the first time can save alot of headaches in the future.