Another 'losing reverse' thread -- but with details!!!

[mickymac]

Hi, I know this problem has been asked before, but it seems like everyone else’s problem is slightly different enough to make me ask the question again.

The car: 1995 Impala SS, 145,000 miles; original everything, no rebuilds on anything. Tranny fluid was last replaced around 100,000.

The problem: losing reverse - still backs up on a level road, but with a intermittent chatter. If I’m going slightly uphill and have to push on the gas — nothing. If I REALLY step on the gas, it ‘catches’, takes off really quick.

All the other gears work fine (I think: I hear it shifting around 15, 25, and 35); the engine ‘brakes’ in manual 1st; the fluid looks old, but I don’t think it smells burnt

The “4L60E common failures” page tells me...

“…“lo-reverse” clutches are worn out, fluid leak in the reverse apply circuit, or broken sunshell. It is possible to help a fluid problem by removing the checkball from its cage in the case in the rear of the trans may help (must remove valvebody), or adding a high-viscosity additive such as Lucas Transmission additive or other seal restorer product. May also have worn boost valve (can replace this by removing the pan).”

A Trans shop told me that it’s the “trans pump” is out, as is the converter, and that I’ll need a full rebuild; he said that line pressure dropped when the car was warm, and no codes showed up (unfortunately, I don’t think I trust him)

Here’s my overly-optimistic thinking: since I’ve still got all the forward gears, my “reverse” problem is a pressure one. Since I don’t have trans pressure gauge or scanner, I’m going to 1) drain the transmission, 2) drop the pan, 3) look for it for clutch material/clean, 4) remove the checkball behind the valvebody, 5) look at the boost valve/replace if necessary, 6) put it back together, 7) add some seal restorer, and 8) drive it and hope it made some difference.

Where do I find this checkball? What does a valvebody and boost valve look like and where can I find them? Does a “worn boost valve” look “worn”? Since they’re only $17, should I just replace it while I’m there?

Can anyone offer advice on this plan of attack? Can anyone recommend a good trans guy in LA?

Thanks in advance.

[cahall]

Chances are either your reverse input clutches or low/reverse clutches are worn or burnt. When this happens, they gain clearance which will usually cause a chatter like you've explained. Low reverse failure is more common in early 4L60E's, because of the slow exhaust of reverse fluid. A broken sun shell will cause you to lose 2nd and 4th also. I think you're looking in the wrong area, if looking for the boost valve to be the problem. Taking that checkball out now is like "closing the barn door, after the horse has got out". The damage is already done...

Frank

[mickymac]

...so full rebuild then? I mean, I'm assuming that this isn't something that can be spot repaired, right?
Follow-up questions: 1) what would differentiate a boost valve problem? 2) Should the trans give me any codes? 3) In rebuilding the trans, does everything have to be replaced, like the torque converter? Is there anything I can do to save money? I mean, there's no way I could rebuild a trans, but I can sure as hell tear one out and put it back in.

[mickymac]

Oh, like I asked before, if anyone has a transmission guy in LA they'd recommend, I'm all ears.

[mickymac]

bump^

[1slow96]

If you're prepared to R&R yourself consider getting one from GM. 36mo./36,000mi. warranty,all new internals.

[The Bolt-On Terror]

Originally Posted by mickymac

Oh, like I asked before, if anyone has a transmission guy in LA they'd recommend, I'm all ears.

Of course, one of the best right there in Calimesa: www.700r4l60e.com