Final Drive damaging transmission
 

Does changing a final drive on the automatic transmission put more parasitic load onto the engine / transmission if you're boosted? I'm running on the edelbrock S/C w/ e85 having my final drive swapped to 4.88 from 4.1. I called the people who installed my final drive and they said that most automatic transmissions that have their final drive swapped will damage the transmission without having my shiftpoints retuned. Now, I'm not sure if theres damage or not but according to D.T there is definitely more load on my engine / transmission than normal.

If anyone with knowledge on rear ends can tune in, that'd be great.

I would say there is less load on your trans. I mean your engine will be having an easier time spinning the wheels .

The damage won't come from additional load on the tranny, but it may come from the TCU not being able to upshift or downshift at the correct engine speed due to the fact that the computer has built in limits on when a gear can be selected based on vehicle speed, rather than engine speed, and you've essentially changed the engine speed relative to vehicle speed.

I'm assuming it can't be retuned right? And yeah that's what I'm talking about the TCU not being able to upshift and downshift at the correct engine speed.

Anything I can do about this?

Think about it in the sense of being in lower gears. Shift points shouldn't matter either as the actual gear ratios haven't changed.

You can change the expected ratio in the tune for an auto.

even if the tcu tables are locked?

TCU changes gears based on load and rpm. It doesn't care about speed (or probably even have the concept of it). Even if it did, that would only be in auto mode and only at partial throttle - and revving higher at partial throttle won't damage anything. Any damage done will be as a result of the increased combined total torque put through it. And lack of cooling of course.

The people you spoke with don't know much about our cars then. I'm planning on getting 4.88s end of this summer or next summer, it doesn't create a higher load. The only damage would be from either the fluids not having an ATF cooler or damage from the extra power the supercharger yields.


You should note, the car will accelerate like a bat out of hell now with a supercharger and 4.88s and cruising on the highway will involve a higher rpm @60-75 but you probably already know that.

@azynneo Titlegore. Phrase it as a question next time yo.

Found out my problem...

Took my car to a toyota dealership to have them flush my tranny. To my surprise, there was engine oil inside the transmission pan! WTF?! I never had my transmission fluid serviced and purchased it directly from Toyota! The viscosity of the oil was that of 0w-20, brown in color. I flushed about 6/8 qts with toyota brand transmission fluid and holy shit! My car is now a monster! No more vibrations in reverse, reduced jerkyness while shifting, while gaining about 20-30 or so WHP and the pulls are now more amazing than before.

I was going to bring my car back to the toyota that I purchased my car from, but from the looks of it, my car is heavily modified and my chances of winning this case would be slim to zip.

Thanks to everyone that replied to this thread, helped me out quite a bit and saved me from having to return back to stock diff finding out that, that wasn't the problem.

If the fluid is brown as you said it really is time to invest in an ATF cooler.

What the hell? 4.88 fd with a Edelbrock SC and e85? That shit sounds like torque city in a twin.

Seems fine to me. Not an auto by the way...

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