Beretta.net

So i havent made much mention of this, but when at idle, i was getting a random knocking from under the car. Only happens at idle in park, or did. Well, ive traced the problem to the transmission.

My question is, what would make a transmission knock at idle? I found out this morning it does it in neutral now too, but when in neutral, ebrake set foot off the brake, when it knocks, the car tries to rock forward just the slightest bit.

Now one day i was goofing off and rocking the car, while off, in park and i heard nearly the same noise coming from the trans when it would bounce off the parking pawl. Im wondering if it is possible for the parking pawl to be bent or broken? The knock does not have that low tone knocking sound that comes with rods or mains. Its more of a higher pitch knock like when you knock your knuckles on the bottom of a transmission pan.

Car holds when Park is engaged, doesnt move. It does not make this noise when in gear foot on the brake. Only in park or neutral at idle. Sound does not go gradually go away when engine is revved, it goes away as soon as the RPMs increase above idle and its quiet as can be. Should I start preparing for a trans rebuild or swap, or whats going on?

Forgot to say, this is on my 95 3100 4T60-E.

Check if you have any converter bolts coming loose. Or a possible cracked flex plate.

If it's not that you could have a bad roller sprag internal to the trans... When the springs go bad the rollers start to lock the sprag when it shouldn't be and cause a knocking sound. Mine did it on my 95 once and when it finally died I lost 3rd and 4th completely. Only L worked on the selector and I could get it up to 2nd gear.

There are two different designs to the sprag... Borg Warner came out with a new version that prevented the springs from touching the internal race which is what causes the failure.



Forward band drum on the bottom right side of the image is the housing, then Parts 652 and 664 are the components... 652 being the bearing and 664 is the internal race.

Essentially it's the first part that goes in the transmission when you build it, after the final drive assy. I built a trans for my 95 and used one of these bad bearings and drove to PA and back for Bfest 06 IIRC and upon returning when I took it apart I found it had started to fail again so I changed to the new version of the springs when I replaced it.

So how do know if its the sprag? Also, is there anything i can do to slow down its breakage if thats whats happening?

Can't he just swap in a 4T60E-HD?

90GTZHO wrote:So how do know if its the sprag? Also, is there anything i can do to slow down its breakage if thats whats happening?

No way other than taking it apart and no way to stop it since its a rubbing part... It will just eventually jam. Mine broke the race into 3 pieces.

and yeah he could swap in a 4t60e-HD if he wanted to or could find one but that requires some changes with axle ends and does not change the sprag type, and it's only the diff that's supposedly stronger... The best thing is to just drop in a 96 4t60e trans. They modified the style and the failure is no longer an issue.

Will i have to do anything wiring wise for a 96 trans? Mines a 95 and still OBD 1.5, wasnt sure the wiring would let me...?

There is no wiring difference... It's a drop in swap. OBDI.5 is much more accepting of a final drive change too so if you were to pick up a trans that wasn't from a Beretta and had perhaps a 3.29 final drive it wouldn't mind. It's when you put a 3.33 or 3.29 in a OBDII car that it throws a code. Stock is 2.96 IIRC...

The only thing that you would have to pay attention to is the differential speed sensor ring... some were 29 teeth and others were 30... so the speedo might be off unless you can find a 29 tooth ring to put on the 96 diff. That is actually an easy swap if you have the two in hand since the diff cover comes off very easily and you can just use a gear puller and hammer and swap it, not even having to remove the diff off the output shaft.

The 3.29 trans are the ones from the w-bodies yes? That being the case, wouldnt i have to swap out the drivers side trans pan too? I thought i remember someone saying they are different from the w-body to the L-body, or maybe that was just for the manual trans'? If thats the case, theres a million of those w-body 4t60e's up here, lots with low miles and wrecked.

So that being the case, i would just need to swap out the diff speed sensor ring and im good to go? Assuming the side pans are the same?

Correct, some don't have the structural side case necessary for the L-body mount, but once again... simple just swap covers as you noted.

And just so im not loosing my mind on the grasping of the concept, i use my diff ring and speed sensor? And the line pressure are gonna be montiored okay by the computer and such...wait a mint, you did this swap on your car didnt you...? lol

You use just the diff ring... the speed sensors are all the same the difference between the two is tooth count... 29 vs 30... Speedo will be off with the 30 teeth. And the PCM doesn't monitor line pressure... its a 60e, not a 65e... All that plug on the front does is the shift solenoids and temp sensor.

I've done at least 3 1999 Transmission swaps into 95's and 96's... The 96 you need to re-tune to accept the gear ratio change but the 95 and older don't monitor RPM vs MPH because the trans component slip code doesn't exist. My pink car is currently it's original 96 trans case and most of the internals... the 95 I had was a 94 trans swapped into that with 3.33 final drive, once I went OBDII I had to fix the gear ratio setting... Long story behind how that got completed with DHP and such.

Sweet! I guess i will be hunting for a 96 4T60-E. Now, can i use the 96-98 4T60Es or does it have to be a 96? Also, how bad do you think my gas mileage will drop with a 3.29 final in it?

96-99 is usable...

Not sure on MPG drop, never did a test. it's not a HUGE gear difference. It's not like my 3.68 and I still get decent mileage since I fixed my going rich at cruise issue.