Is an auto tranny shift kit supposed to "clunk" into the next gear? THUD!


#1

Friend has one of these. When it shifts, there is a loud jarring THUD.
Is that what its supposed to do?


#2

Read the box it came in to see what it’s supposed to do…If it promises “Firm, solid shifts” then that’s what it’s doing…But they forgot to tell you, at low throttle settings, the hard shifts can be very annoying…


#3

so floor it man!


#4

Yeah! Get some satisfying second gear scratch!


#5

Friend bought it like that. No box.


#6

I suggest that you not take automotive advice from your friend.

No, that is probably not supposed to happen, but if one puts unknown secondhand stuff on one’s car, one gets what one gets. So, now, does your friend know why he probably got this thing secondhand for such a great price?


#7

Describe car. Year, model.


#8

This is the downside of setting up a street car with racing stuff.


#9

And used racing stuff of unknown history at that…


#10

I think what the OP is saying is that the shift kit was in the trans at the time of the purchase of the car.

You might go back to the seller and see if the original parts were kept. Shift kits usually involve stiffer accumulator springs, blocked accumulator passages, altered valve body plates, removal of select passage balls, etc. So for the price of a few gaskets the original kit can be reinstalled.


#11

Here’s the answer to smooth shifts. put a 27’ trailer on it !

My79 shifts…uhm…’‘decisevely’’ unless you load it up. Then it shifts as smooth as glass.
27’ trailer,
pallet of pellets,
bed full of sod.


#12

Ok, let me ask the question again, b/c I don’t think I was clear.

When a car like a 1990s Firebird has an AUTO TRANNY SHIFT KIT installed, is it supposed to THUD into the next gear? Yes or no? Thanks!


#13

A shift kit does provide firm shifts, enough to chirp the tires sometimes. The hard shifts do take their toll on the drivetrain, especially U joints. You could have a bad U joint or driveshaft bearing causing the loud thud. It could also be a loose gearset in the differential.


#14

There are different types of shift kits. Some are mild and meant for the ho-hum daily drivers.
The high performance kits are for those who race (street or strip) and want those gears banging with driver comfort not a factor.

So yes, a shift kit can cause a firm/harsh/thud shift but so can an internal transmission fault or a broken transmission mount.

What year Firebird? I seem to remember a transmission hard shifting bulletin about Camaros/Firebirds of the 90s era. Thinking it was 96 up; just not sure.