I have a turbo 350 that was freshly built when I did the roadster.Originally I had a low mounted Lokar dipstick that was a PIA to check fluid levels and I am sure it was run for several hundred kms with low fluids.I changed to a firewall mounted dipstick and can now easily check the fluid and assume the Lokar unit is accurate. When I put it into drive or reverse there is a definite "clunk" as it engages. The trans does everything else right,changes up and down(set up a proper vacuum for the modulator of the manifold) and if I use it manually shifts great. Does not drop any fluids so it is all staying in there. I checked the torque convertor bolts and they seem tight. Any suggestions???
Check the yoke that slides into the back of the transmission for slack. Also, the u-joints, differential, axle splines, etc. Dave.
If you're sure it was run low on fluid for a considerable distance there is probably a good chance you have ruined the planetary gears in it. On just about all hydramatic transmissions, the fluid level (when hot) will be just about to the dipstick hole level (on level ground) with the pump running (engine running). Knowing that, you can easily make your own dipstick or check the accuracy of any aftermarket dipstick that you may have.
Check your mount and Ujoints too but TH350's do that. They don't have an auxiliary a forward clutch accumulator like the 700R4. If the forward clutch pack was built tight or with out the wave plate it will have harsh engagement forward and reverse engagement. Removal of the wave plate or building the forward clutch stack tight is a common performance upgrade many rebuilders do automatically. This is a modification that makes the transmission shift crisply and certainly is necessary for a TH350 to live behind a high HP motor. By contrast a 700R4 can be setup to bang every gear hard but still offer smooth engagement because of an extra accumulator in the Aux valve body added for this reason. The TH350 doesn't have this. I have a 7004R that will chirp the tires in 2nd and 3rd behind a high HP motor but engages smoothly forward and reverse and shift very smoothly at part throttle. A properly setup 700R4 is amazing and almost no electronics.
Look in the rebuild instructions for the anti clunk spring and try to remember if you installed it, This isn't a wisecrack, there really is one in the TH 350s and what you described is what happens when it is broken or left out.
That sounds interesting.Everything in the car is new,tail shaft,yokes, universals(no slack in them) and diff rebuilt. I will take it down to a performance auto shop and have him look at it too. I didn't build the box.It was done by a specialist guy who builds drag cars etc and he does a good job.But not local to me unfortunately.
. . The 350 in my daily 80 malibu wagon does the same thing and everything is new. Trans has had some modifications and I've learned to live with it.
Is the noise a clunk or more like a loud click? If its more like a loud click, it could be from where the center support is splined to the case. Th350s were very common to wear the lugs in the case and then the center support moves back and forth in the case when shifting into drive or reverse. Many trans rebuilders will use a case that has just too much wear in the case lugs and then use what is called a Case Saver instead of the factory cushion spring to limit the movement. The downside to the Case Saver is it the trans can make noise when put into gear. Bill
I assume you're speaking of the very stout spring that normally resides under the accumulator piston that's part of the valve body? Many shift kits instruct you to remove and discard this spring. It does make them engage very harshly.
Ah...I guess I never knew what that was called. I never leave them out - I have pondered many times before just wtf that was - but I do know that if you leave it out of that fitting, the installed hardware is left kinda loose and sloppy.
Thanks to all for the responses.Mike Miller responded to my PM and advised that the box has to come out to rectify the problem.It shifts from 1st to 2nd to 3rd smoothly.Just the clunk when you engage drive/reverse. It isn't causing any other issues so I think I will leave it for the time being and live with the clunk.
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