Question about lash, or play in drive line on an 85

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Langsmer
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Question about lash, or play in drive line on an 85

Post by Langsmer »

Hello all, forgive me if this has been covered. I wasn’t able to find anything on the subject.

I have a new to me 85 SR5 manual with an issue of slop in the drive line somewhere. When you let off the gas it takes a moment then there is a clunk. When you step on the gas there is a clunk again, as if there is play somewhere in the driveline. This makes cursing at a steady speed on a flat road difficult as any slight lifting of your foot of the gas, or any slight decline in the road causes the clunk.

Also worth noting, it’s not audible. You can just feel it. There is no rumbling or grumbling when cornering. There is a light whirring when accelerating or traveling at a steady speed when the window is down. Other than that it seems fine. The engine revs up and down without hesitation. The problem seems to be slack somewhere.

Any idea where to start on this? Thanks!
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Re: Question about lash, or play in drive line on an 85

Post by BaileySims »

If I were to make some what of an educated guess, I'd seem to think it would be the motor mounts/trans mount. Seen plenty of blown out mounts in action. When you were to hit the throttle, the engine turns to one side before any movement of the wheels occurred creating that feeling of what you describe.

This is just a guess, someone will chime in soon with a slew of other useful information.
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dlb
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Re: Question about lash, or play in drive line on an 85

Post by dlb »

This is a common problem, see #5 in this FAQ:

viewtopic.php?f=2&t=7442

I've personally found it in strut mounts and worn CV axles. You have to basically take the front wheel hub assembly off to accurately diagnose where your clunk is coming from. It's actually not a huge job if you're handy and have tools.
Langsmer
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Re: Question about lash, or play in drive line on an 85

Post by Langsmer »

Dang! Sorry I didn’t see that in the FAQ’s. That gives me a place to start. I’ll report back when I have more info. Thanks!
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Re: Question about lash, or play in drive line on an 85

Post by Petros »

sounds like engine/trans mounts to me as well. Possible you have bad CV or u-joints, but typically you get other symptoms if your cv joints are bad (clunking in a turn while accelerating). Also, check the center bearing mount on the drive shaft center bearing. It is rubber so it should have some flex or give, but it is blown out it will flop around in there and make a clunch on accel/decell, even if not in 4wd.

There is a remote possibility there is something wrong or out of adjustment on your carburetor or emission control system. there are devices that cut off the fuel flow when you are decelerating so it will allow unburnt fuel out the exhaust system, that can also cause it to act like it clunks. There are also several linkages that need to be adjusted correctly or it will act odd on accel/decell.
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Re: Question about lash, or play in drive line on an 85

Post by ARCHINSTL »

Ditto on both dlb's and Petros' advice!
In '06 I renewed the engine and trans mounts and much of the clunks went away.
In '07 I replaced ALL of the front bushings, strut inserts, and springs, but a clunk still manifested itself on occasion.
In '10 I replaced the rear driveshaft and support bearing and that was it!
Well - on occasion on leaving a driveway when the wheels are turned to the right, I still get a slight clunk which is apparently from the rack's right bushing, so ...
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Langsmer
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Re: Question about lash, or play in drive line on an 85

Post by Langsmer »

Well, I think the clunking issue is actually a fuel system issue.

The fuel system is this car is much more complicated than I’m used to (60’s VW’s) and is very intimidating. I tried to clean up the EGR and now the car is running really poorly. I’ll poke at it more tomorrow.
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Re: Question about lash, or play in drive line on an 85

Post by ARCHINSTL »

Check this out on my EGR cleaning:
viewtopic.php?t=1496&highlight=egr/
Note that this is before I gave up on the OE carb and emissions spaghetti and went with a Weber (MO now has no emissions inspections for pre-'96 cars).
The only "emission item" I've kept is the cat - since it is from 2005, I have NO idea if it still works!
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Langsmer
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Re: Question about lash, or play in drive line on an 85

Post by Langsmer »

Thanks Tom! I got it cleaned up. Haven’t noticed a real difference after cleaning it up, but I figured out that I had created a vac leak when putting it back on. I got that fixed as well as tracked down another leak around the base of the TVSV. It still seems to be leaving vacuum from somewhere else so I’ll keep poking around with a propane torch and carb cleaner. If I can’t get the stock carb to work well after tinkering with it I may move over to a Webber. My Datsun 620 has one and it’s really simple. It just doesn’t do very well when it super cold out, where the stock Toyota setup on this car seems pretty good on chilly days.

Thanks for all the help folks!
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Re: Question about lash, or play in drive line on an 85

Post by Langsmer »

Alright, I’ve been going over and driving the car a bit more over the last few days. It seems to be running pretty poorly after unclogging the EGR. Here is a list of symptoms from cold start.

1. Pump pedal a few times. Car fires right up.
2. Car revs up, then almost stalls, then revs up, and does this over and over until it starts to warm up.
3. Car idles somewhat erratically at any temp, but gets somewhat even after it warms up. The reving at cold is new, but the erratic idle has been the case since I got the car.
4. The car is gutless since the EGR cleaning. Take off is painfully slow. If driving at a steady speed you can feel the car is putting out power erratically, like at idle.

I have gone over the vac lines with carb cleaner and replaced any that seemed too crispy. I found two leaks. One at the base of the tvsv (which I fixed with high temp silicone), the other at the back of the carb. There is a puddle of old dried gas on the heat shield below the leak. (Update: if I shoot carb cleaner right at where the throttle spindle enters the carb in the back there is a very significant jump in rpms)

This I will work on figuring out, but I’m a bit perplexed. The car didn’t run great when I got it, now it runs like a total turd. Could just unclogging the EGR do that? It seems like a pretty minor player in the fuel system. I am going to run an experiment tonight by blocking it off to see if that helps at all bringing it back to as purchased condition (update: it didn’t make a difference). Also, if I unhook and plug the secondary accelerator pump and line the car runs really poorly. Unfortunately I have to drive the car a couple of times a week and hate doing it with it running this poorly.
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Re: Question about lash, or play in drive line on an 85

Post by Petros »

sound like it could be a vac leak, or something else. all you can do is check all vac operated componets, and check for leaky manifold gasket, etc.

Next is to double check all of the routing of all of the vac lines. If a vac line is plugged in the wrong place it will act badly, like a vac leak.

check your float leavel through the glass window on the front of the carb (you will likely have to clean it off), and check the AAP vac line for leaking fuel. if you find fuel in the vac line cap both ends. and see how it runs.

There are a number of carb adjustments for linkage, choke, etc. go over all of those to make sure the are set properly. See the FSM under fuel system.

It is important you verify there are no vac leaks, and all of the vac lines are routed properly. No other adjustments will work to fix it if you still have a vac leak.

Also consider the problem may not be carb or fuel system related, might be a weak spark or something else.
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Langsmer
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Re: Question about lash, or play in drive line on an 85

Post by Langsmer »

Petros, thanks. I picked up a copy of the FSM and will start running through all the systems more methodically. Thanks for the help!
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Re: Question about lash, or play in drive line on an 85

Post by dlb »

Cleaning out the EGR shouldn't have the effects that you are running into.

On previous tercels I've owned that ran poorly, I often found vacuum lines were hooked up incorrectly. The routing of them can be very confusing, especially with some hoses hooking up to metal lines that disappear from sight, so what I like to do is disconnect the hose in question at both ends and blow into one end and confirm that air is coming out the other end. I've found that's the best way to confirm that each hose is going where it needs to go.

A common failure that you might check is the AAP diaphragm on the carb. There is a hose that runs from the AAP on the front of the carb to a manifold vacuum port on the intake manifold. When the AAP ruptures, the vacuum then sucks gas through the hose, into the manifold, and eventually into the first cylinder, which causes all kinds of running problems. At this point you need to go over the entire vacuum system (which sounds bad but actually just involves sucking on a few hoses, really) but the AAP fails often enough that it's worth checking first.
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Re: Question about lash, or play in drive line on an 85

Post by mrdance123 »

I have very similar issue with drive-line slop, as described by thread originator "Langsmer". I also get a heavy clunk and jerk when the drive-line torque changes back and forth between positive accelerating to negative decelerating. It feels like towing with a chain when it snaps tight and jerks the car backward, or riding a roller coaster when it latches to it's drag hook and being jerked forward..... not this extreme... but you get the idea. The jerking feels exactly the same, either forward or back, giving more gas or letting up, making the drive torque reverse. I'm always been in FWD, have not tried it in 4WD yet, but plan to. (I'll bet this will reduce jerking, will report on it later). I have 3 T4s to compare, only this one problem car does it annoyingly. The others do it slightly but is virtually un-noticeable. I jack up one front wheel off ground, rotate it to check for rotational slop when it is in gear. Problem car: 2" slop in 1st gear, 4" slop in 5th, measuring on the tread. Same slop on both front wheels, done one at a time. In 5th is it very easy to turn the engine from the wheel, so watch the alternator pulley to make sure it not moving to make measurement. Always in FWD, not 4WD. The 2 other cars have much less slop play, about half the amount. I'm inclined to believe that the front differential is severely worn, out of adjustment internally, maybe near the point of failure. Hopefully someone who has done work rebuilding differentials can chime in with their thoughts... Thanks.
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