A442F (hydraulic model) torque converter lock up questions (1 Viewer)

[torqueluvr]

Tried search, to no avail.

Get ready for a doozy of a post.

1992 HDJ81 245k, vin plate says A442F, and from my research it is the hydraulic model because it has the 7 digit gear indicator (PRDN321). Also has Mark's part time 4wd conversion, and the following symptoms all happen when the hubs are locked and unlocked, and when the centre diff lock is engaged, which in my case would be 4HI with the hubs locked.

Issue #1
I've been told 3rd gear locks up the TC in this transmission. However while in 3rd gear, the rpms will still dance around if i play with the skinny pedal, similar to as in 1st and 2nd. This is all while in D. Once I hit overdrive speeds, about 62km/h on my speedo with my 33s, I can clearly feel it lock the TC. And other than it locking a little earlier than I would like (thanks to the 33s), the lock up is absolutely glorious. What worries me, is when in D, but in 3rd gear, the rpm's still dance up and down with the skinny. I thought it was supposed to lock. Thoughts?


Issue #2
When in D and in 3rd gear like I said it still dances around. But if I shift the shifter to "3", I can feel the rpms jumping up a bit like the TC WAS locked in 3rd, but not fully. While in "3" the rpms still dance with the skinny, but at a higher RPM than in "D" in 3rd gear. I hope this makes sense. At first, it seems like in D it will not lock in 3rd. But once I manually move it to "3", the rpms jump up and I feel a clear change in gripping power. I hope I'm explaining this properly.

Issue #3
When rolling to a stop and stopped at a light, when the light turns green and I take my foot off the brake on to the skinny, immediately as I take my foot off the brake I feel a slight yet very noticeable clunk, and the shifter jolts a little bit, which makes me think it is trans related. It's like it was stuck in gear or something while slowing down, and then when I take the brake off it fully disengages, and then re-engages. This is all when I take my foot off the brake, it has nothing to do with the gas pedal.

Does this make any sense? Or is this how they are supposed to be.

I bought the truck in November and I am not aware of any tranny maintenance by the PO's. I have a lead on a used A442F that I'm thinking of bench rebuilding overtime so I can still drive my 81 as a daily until I'm ready to install.

 

[IanB]

Fully hydraulic A442F only has 4th gear lockup, you'd need a wholesale transmissions valve body upgrade to get lockup in lower gears.

It's possible that you are mistaking "3rd in D" for 4th with TC unlocked. Try driving in 3 and then shifting to D to see what the RPM's do, this way you'll KNOW what they are for each situation instead of trying to work backwards. When the TC locks up it's very noticeable, but could be confused for a gear change. OD = 4th on these transmissions.

This clunk is likely driveshaft bind, grease the shafts and see if it improves at all. Also give your u-joints an inspection to make sure they are still good.

 

[Greg_B]

The clunk may be an accumulation of all the driveline lash, but as IanB mentions, check your driveshaft splines (make sure you index before taking apart - if you're going to - to clean, inspect and regrease the splines), ujoints and driveplates on the front axle. If yours has the early driveplates they do not engage as much of the outer axle spine so are known to wear quicker.

You can update the driveplates if that is it, but you would have to do the birfields as well.

If you do a search in the 80's section about driveline clinks you will have reading for hours. Many narrowed it down to the driveshafts after eliminating driveplates and here is a small sample with lots of discussion: The OFFICIAL clunk/thunk driveshaft thread

On a sidenote, does your 81 have viscous coupler(VC)? My understanding is the VC can reduce driveline lash clunk/feel but not excessive wear or driveshaft clunk.

hth's
gb

 

[torqueluvr]

Thanks for the replies, gents. I have some homework to do.