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did i make my car even slower??

Grimsin

Grimsin

New member
so bit of a back story.
2005 impala ls, 3.8l gear ratio 3:05.
I bought a 2011 buick lucerne transmission, 2:86 gear ratio. only 6000 kilometres on it.

The plan was to take my 3:05 gears and install them into the new buick trans. and install a transgo shift kit.
so we took these parts out of my trans and put it into the buick trans.


with the old trans first gear would go from 0-50mph then shift to 2nd.
now with the new trans i go to 55-56 mph before it shifts....
I have no check engine light, would the check engine light come on if the gear ratio is 2:86?
everything else works 100% it shifts like it was brand new, love it, just wondering if i actually did change my gear ratio and if so why does it shift at 55 mph not 50 mph like it used to.
 


no, because we put the 3:05 gears from the impala trans into the buick trans. at least we thought we did.... that's why im asking if the picture above is the parts i needed to swap into the buick trans to make it a 3:05 gear ratio
 
for some reason I thought the 2.84 fdr was due to the 2.93 chain and the 3.05 diff where the "3.05 fdr" trans is the 3.29 chain and 3.05 diff

the 3.05 fdr diff has planet gears that are quite small, small enough I don't think they make the 2.84 FDR trans as its own differential.
 
you confused me lol, so did i change the gear ratio to 3:05? or is it still 2:86? OR is it something really wierd now?

i did reset the pcm, if the gear ratio is different what happens when the pcm relearns the trans shift adaptives? will i get a check engine light?
 


did you compare the two diffs?

if the teeth number of the sun or planets matched then you just replaced a 3.05 diff with your old 3.05 diff (assuming im correct in the 2.84 FDR trans having the 3.05 diff with 2.93 ratio chainset.

basically you might have a 2.84 fdr.

put the shifter into 3rd/non overdrive and scan for calculated gear ratio. if its not .98-1.02 then your likely a 2.84 fdr (it would probably read close to .90ish)

then again it could just be the trans shift adaptives haven't learned.
 
lols.
if i do have 2:86 gear ratio wouldnt first gear at wot shift way later, not just a 5mph higher?
i hope its just trans shift adaptives and i actually have 3:05 gears.
 


billboost whats your opinion?

im gonna go drive around try to to if relearn the trans shift adaptives see if it helps.
 
so ya its a different gear ratio.. in first gear at 40mph with 3:05 gears i was @5000rpms, now with this trans at 40mph im at 4000rpms.
this really blows...
why is it that am i not throwing a check engine light or anything if the gear raito is different?
 
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According to the book info that I've read all NA ratios were derived with a 35/35 drive driven ratio and only the diff change.

Easiest way to be sure.. fire up any GPS speed checker on your phone and see if your speedo is off.
 


As long as he kept the same diff, he shouldn't have changed the reluctor on the diff. Which is how it reads the pulses per mile.
 
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