99 V8 SHO - Intermittent Reverse won't engage

[qiksho]

Hey Guys,

My Dad's 99 SHO has decided to only engage reverse when it wants to. Sometimes it will go into reverse, other times it will act like it is in neutral. Putting it back in park and then back into reverse will sometimes get it to engage. This car has not been driven since the problem arose as to not cause damage to the transmission.

We have plenty of mechanical ability and a shop to work in, however are not real well versed with automatic transmissions. What do you think might be the problem?

I did some searching and found a TSB on V8 SHO, however it doesn't give a whole lot of information. Here is the TSB - 98-3-7 FEB 98 Intermittent Neutral Condition, No Forward/Reverse, AX4N.

Any input on this condition is appreciated.

Thanks,

Brandyn

 

[rick-ng]

Maybe its the electonic shift selecter...

 

[93rev2sev]

or it's low on fluid?

 

[SHO Dude]

If all the other gears are working OK, it's blown a gasket between the chain cover and the transmission case. There pressure passages between the chain cover and the case to get fluid down deep into the transmission housing. One of these passages is Reverse Oil. It's on the end of the group and doesn't have a lot of support around it. Reverse is a high pressure gear and hits with about 150psi of line pressure. This pressure and the fact that the structure there doesn't have a lot of support and cause the gasket to slip out of position and fail. This leaks line pressure and reverse won't apply.

See this picture. I have circled the pressure passage in the case that supplies revers oil. As you can see, the closest bolt is a ways away, so the structure isn't really strong right there. The new '99 gaskets are thicker right there and keep this problem from happening again.



When you take it apart, you'll proll'y find the chunk of gasket missing or hanging on by a thread.

 

[SHO#7]

I would also inspect the **** tubes in the bottom pan. The one applys reverse. They have a little issue with getting loose.

Mike