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General Discussions about the 300M

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 #377687  by adu1982
 February 8th, 2019, 9:49 pm
So today I think I finally started to feel the transmission going. About 700-900 miles after the code for torque converter first popped up. I know some got away with replacing the converter but for how cheep trannies are around there is no point as the rest of it (internal transmission parts) has 200k.

I saw on car-part there are 2 id numbers (one being for the 2.7 engine cars correct?) ...4799940 and 4799941.

The 2.7 (4799941 looks like, am I correct?) around me they show have a lot lot less miles, and there are quite a few. Two with 58k and 59k of 01, 00 intrepid, and also nearby. The 3.5 ones , just one at just under 100k but its 2 hrs away.

Is there something that needs changed to put a 2.7 tranny in my 01 LHS . Im not looking to change anything for improvement or what not just don't want it to break down, she has given plenty of notice now (unlike the pos Buick rdvz who just crapped its tranny with no warning this week).
User avatar
 #377698  by In-trepid
 February 9th, 2019, 10:24 am
I would just make sure to stay in the same year range so that cables, sensors, etc are the same. As for the transmission themselves, the final gearing ratio on the 2.7 and the 300m Special is different than all of the others for the 3.5. You can easily change the sprockets and chain with the original to get it back to the right final gear ratio. As far as internals and bolt up they are identical.
User avatar
 #377720  by adu1982
 February 9th, 2019, 5:42 pm
Neweb question here but? Sprockets and chain in the transmission? I'm guessing I would use mine as a donor ?

Also if I did note it here yet, my tranny has thrown a torque converter code.

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 #377726  by In-trepid
 February 9th, 2019, 8:26 pm
Since it is in the LHS with a 3.5, it will have different final gearing than a 2.7 transmission. You will need to take the sprockets out of the original and put into the new transmission. The chain will be the same in both, so it doesn't matter which one that you use. You will also need some 90 weight gear oil as technically the sprockets and chain are the differential of the transmission. Otherwise it should be a pretty straight forward swap.
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 #377727  by adu1982
 February 10th, 2019, 1:03 am
Is replacing the sprockets pretty involved or fairly easy.....any chance of messing up something in the tranny itself...... ?

58k sure beats 145k , and cheaper I think (all thanks to all the 2.7 blown engines)....

I did replace the sprockets in the special , as the donor engine was a 99 , when I did my engine swap (my biggest repair to date still).

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User avatar
 #377733  by Mottman
 February 10th, 2019, 9:20 am
Adu1982,
Do it wrong and of course you can screw up anything.
But swapping the sprockets & chain is not hard.
Each of the sprockets are held on by a big snap ring.
I removed the snap-rings, wave washers & shims
laying them in order
( as if they were like engine piston rings, so they go on
in the exact same way as they came off )
Then, with a little wiggling, slid the chain & sprockets
off the shafts as one unit.
Dont forget the snubber.
Use the one that will provide the best lash.
I think there were 3 different ones,
identified by color.
Each color provided different lash adjustments
( Best check the FSM for more info on this. )

You will need some good gasket sealer. I used
PERMATEX, ULTRA BLACK to reinstall the rear cover.
( there is no gasket between the transmission-housing
and rear cover. )

It can be done in the car.
But it is alot easier with the trans. out.

Some more advice on transmission swaps.

Yes, you will also need some differential-gear oil as well.
Most salvage yards drain all fluids on transmissions
/ drop the pan to inspect for debris /damage.
( at least they should ! )
And they DON'T install a new gasket or reseal the pan.
( Part of any automatic transmission warranty entails
you or you'r mechanic installing a new filter & fluids )

The chain & sprockets actually ride in transmission fluid
( not differential oil )
What I have personally noticed is that most shops are
UN-aware of the differential being completely separate from
the trans. fluid on these transmissions.
In other words, don't be surprised if they didn't drain the
differential. Most likely the fluid is due to be changed anyway.

Extremely important !
Dont forget to reverse flush the trans. cooling system BEFORE
you connect the cooling lines to the trans.
And make absolutely sure the cooling system is not clogged.
Chrysler recommends using mineral-spirits.
I used low pressure 30 psi compressed air, followed by mineral-spirits,
followed by / pushed with more air, finished with ATF+4 pushed through with
more compressed air.
If the cooling system is still clogged, its usually the secondary
plates & vanes cooler that will not UN-clog ( it has tiny passages
like an A/C condenser )
If you cant UN-clog it than you must replace it.
I used a large HAYDEN pipe style, truck cooler.
User avatar
 #377765  by adu1982
 February 11th, 2019, 11:06 pm
Thanks for all advices guys, you are the best.

My dad just bought a 2018 Pacifica, 20k miles. So now I am tackling the Buick tranny swap. Got my base back so the lhs will just sit. If nothing went bad she might be clean, but I did drive it a bit , even though I could have and should have not . I will drop the pan just out of curiosity before I'll pull it out and check for shavings or coffee grinds....



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User avatar
 #378006  by adu1982
 March 1st, 2019, 10:39 pm
Thanks for the info Brian.

What did you use to blow compressed air at 30 psi (I don't have a compressor , but it might be high time for one) ?

I do have a tire inflator , but don't know if that is strong enough......from what I've seen on YouTube they just use compressors.

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User avatar
 #378013  by Mottman
 March 2nd, 2019, 3:33 pm
Adu1982,
I just used a small pancake compressor.
User avatar
 #378737  by adu1982
 April 22nd, 2019, 9:57 am
Does anybody know what the speed difference (mph at the cluster) is if I don't change the final gears?

I ask because my last 2 speeding tickets were really not "wanted" or "needed" and my crazy thought is thatbmaybe it will help if my real speed is a few mph lower than what I keep my foot on it at.


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User avatar
 #378803  by adu1982
 April 25th, 2019, 6:49 pm
Well I opened up my transmission, and taking the chain off is not too hard. Only problem is that in taking the bolts of the chain housing (at 205 k transmission, even with care and pb blaster ) I broke 2 bolts that hold it. Since the only impact is that the speed is a bit off from what I understand , I'm thinking to just install it as is. At least I'll be able to see what the speed difference is and repost it here for posterity and worse case I can just swap it later as I will keep my chain. Waiting on subframe bushings to come and swap them and then hopefully I can install it. Then all she needs is taupe dash & paint ( and some more parts that I have in stock). Never ends I guess

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User avatar
 #378804  by adu1982
 April 25th, 2019, 7:31 pm
Scratch that ,just investigated, añd found out it should actually be quicker cause of the 3.89 gears (which some here have added to 3.5). .....I had forgotten.....


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User avatar
 #378920  by adu1982
 May 3rd, 2019, 9:28 pm
After a few days of hustle , the transmission is in. A bunch of things replaced too. Going for an alignment tomorrow after an early quick shift at work.


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