uhh... is my 904 "chirping" under hard upshifts???

-

MRGTX

Well-Known Member
Joined
Sep 24, 2007
Messages
2,198
Reaction score
728
Location
CT, USA
A few years back, I had my 904 rebuilt to handle more power from a built small block as I prepared for the new motor. My swap from the 318 to 5.9L Magnum was a big jump but I foresee more power coming down the road and wanted to build it accordingly.

So Best Transmission in Springfield, MA has been around since the 60s and the owner has a good reputation for muscle car and drag racing transmissions...I don't have the complete list of upgrades that were installed but upgraded bands and clutches along with a ~5800 RPM governor weight and a TF2 shift kit were part of the build. I am also running a TCI 2600 RPM converter and a deeper pan. Best Transmission admitted that they had built very few Chrysler units but they were confident that they could rebuild it the way I wanted it. I opted to not go for a manual shift valve body, mostly because of the column shift...

So I have only put a few hundred miles on the car since getting it back on the road last year and aside from not having the kickdown linkage tuned yet, the transmission seems to perform fine under normal driving.

Because I still have the fragile 7.25" rear (with the 2.76 ratio) I haven't hammered on it at all....but on the few occasions where I would wind it up a bit (usually shifting manually around 5k) resulted in a chirp specifically not coming from the tires, that I THOUGHT was a belt slippage on upshifts...but after checking the tension on the (brand new) belts...this theory started to fall apart. Honestly, it doesn't make sense that this scenario would cause the belts to chrip anyway since an upshift would slow down the alternator and fan...not speed them up.

So I'm starting to worry that the noise is coming from the 904 slushbox itself.

I'm MUCH more familiar with manual transmissions and nearly every other car I've ever owned has had three pedals...so please excuse my ignorance.

Is this plausible? What would it mean for the transmission?
Yes...the fluid level is good... What else should I check?

Thanks a million for any thoughts!
 
Just a thought.
I have a dirt bike that I put a high performance clutch in and it barks (chirps) when hot on a low speed hi torque engagement depending on the oil I run.
What fluid are you running?

Your chirp may simply be clutches or the band taking hold.
 
Because I still have the fragile 7.25" rear (with the 2.76 ratio) I haven't hammered on it at all....but on the few occasions where I would wind it up a bit (usually shifting manually around 5k) resulted in a chirp specifically not coming from the tires, that I THOUGHT was a belt slippage on upshifts...but after checking the tension on the (brand new) belts...this theory started to fall apart. Honestly, it doesn't make sense that this scenario would cause the belts to chrip anyway since an upshift would slow down the alternator and fan...not speed them up.

So I'm starting to worry that the noise is coming from the 904 slushbox itself.
Have had this as well.
Not liking it.
 
Thanks to all for the suggestions.

..
Your chirp may simply be clutches or the band taking hold.

Ok...but this would be a sign of a problem, right? I gather that they're not supposed to make an audible sound...

Have had this as well.
Not liking it.

Is your transmission built as well?

Check your U joints.

The u-joints have always had a little bit of slop in them (at least since I got this car in the mid 1990s) but that has ever only manifested as a clunk when I put it in reverse and never got worse over the years...It's a very different sound.
 
Yes built by a reputable local guru. I was told it was nothing to worry about but I don't like it. Might recheck adjustment on bands. Swapped from a built 318 to a mild 5.9 magnum.

It sounds like we're in exactly the same boat here. former 318, now with a Magnum 5.9L.
Yours is also a 904, not a 727, correct?
 
The u-joints have always had a little bit of slop in them (at least since I got this car in the mid 1990s) but that has ever only manifested as a clunk when I put it in reverse and never got worse over the years...It's a very different sound.

Well, I guess you can just ignore them, lol. When they get dry, they can an do chirp occasionally. The "clunk" that you are having is probably the notorious Chrysler clunk, that is commonly found in a 7 1/4 rear.
 
That clunk in the rear is the spider to side gear clearance, and when they make that clunk, they are way past their best-before-date. I take them apart,grind off the unused steps,reset the clearances, and end of clunking!

But sometimes there is more to it than that. Sometimes the cross-pin hole is wallered out (thanks RRR for that great word), and the pin is about to get launched. And when that happens everything back there stops turning.This usually has a bad ending.
 
said your kick down linkage ant tuned,..get that right, idk if it has any thing to do with your issue, but if ya dont could burn up your trans!
 
-
Back
Top