I have a 97 SSEi. I'm getting a whirring noise while accelerating until I hit 30mph. It comes and goes. It started after I replaced my mounts and did my lower intake manifold. My buddy says it'* the trans pump, but I'm looking for 2nd opinions. Also, I need to know what size pan bolts my trans has, 6 or 8mm. Any help is appreciated, thanks!

Does the whirring noise increase with road speed or engine RPM'*. In other words, if you are driving at 25 mph and downshift one gear (maintain road speed), does the whirring increase or stay the same. Also, if you are driving at 25 mph and you shift into neutral (let the engine idle) does the whirring go away. A few quick tests will tell you if the noise is transmission, engine, or drive train related.

The noise does increase with engine rpm. It goes away when it'* in park or neutral as far as I can tell. That'* the reason I believe it'* transmission related. I tried revving it up in neutral to see if it was the exhaust and I thought I heard it a little. It'* hard to tell though because I have a magnaflow muffler that makes more noise than my car sometimes. But for as I can tell, it'* only while the transmission is "engaged". Also, the noise isn't there when the components are cold. I checked the trans fluid around the time it all started and it was at the bare minimum. I filled it so when I checked again it was in between the hashmarks but the noise continued. Like I said the noise seems to go away around 30 mph. I will double check here shortly to make sure the noise goes away while driving and shifting into neutral at speed. I'll get back on in a few hours and update this post. I spoke with the place that replaced my transmission and the guy told me there was no such thing as a 4t65e-hd transmission, just the 4t65e. I don't know the exact difference but maybe when it was replaced, they used the wrong one? Also, it seems to hold a little between 30 and 40 when it'* trying to shift. I don't get much get up and go. I have to press the pedal down more than I feel I should and I was wondering if maybe that'* trans related as well. Thanks again for the input.

L36 engines have a 4T65e, but they have the light duty version, RPO code M15. L67 engines have the 4T65e HD, meaning heavy duty (RPO code MN7). The MN7 version has a larger differential, and due to the larger differential, the output shaft on a MN7 is about 1/4 inch longer. The MN7 also has a stronger input sun gear, and has roller bearings on the differential housing whereas the light duty 4T65e have a bushing instead. There may be some other minor differences inside, but these are the major ones.

OK. I checked to see if it only made the noise while in drive and it doesn't. It makes the noise while in neutral but it'* less noticeable and I can only assume it'* because there'* less load. Thanks for the explanation of the differences. I only knew that the HD was heavy duty..

If you hear the noise in neutral there is a good chance it is coming from wheel bearings or CV joints on the half shafts. One other thing you can check (if you haven't) is while maintaining steady speed of 25 MPH drop it down a gear or two to increase the RPM'*. If the whirring noise increases, it may be engine or transmission related. If it stays the same, I would look at bearings and CV joints.

Just wanna add incase someone reads this down the road. 1995'* have the 4T60-E and some 1996 L67'* have the 4T60E-HD.

How long ago did you have the tranny worked on? I had a tranny rebuilt on my 89 SE . The guy put a new input sprag in it when he rebuilt it. The part was for a different model year and it was like a 1/8" longer. The end of the sprag rubbed on the aluminum housing and tiny aluminum shavings went everywhere. Check your fluid and make sure it is not turning grey. I won't tell you the rest of the story unless you need to know.

I had the trans replaced about 12000 miles ago. The mechanic keeps telling me that there was no such thing as the 4t65e-hd transmission. Now I called the GM dealer in my area and he told me that according to their information systems, the 1997 l67 was the year the 4t65e-hd was introduced and it came standard on all 1997 SSEi Bonnevilles. But I'll keep at them. I did figure out what the noise was, I separated my exhaust at the end of the exhaust manifold where it meets the "downpipe" and my dumbass didn't replace the gasket...