I have a theory that I'd like to run past you pros that know about transmissions.

A little history. My '95 N/A 850 with auto trans has the jerks once in a while. I'll have it in gear at a stop light, press the gas to go and it will hesitate for a second then as a press on the gas slightly more, it engages and the car moves. Usually with a jerk. It will also do a jerk when I'm at the last downshift before stopping.

Here's my theory, is it possible that this is a vacuum leak? I'm guessing that the vacuum is at it's lowest point both when first starting from a stop and when stopping. And if I'm correct, haven't looked on the 850 yet, doesn't the trans use vacuum for part of it's operation? If it is a vac leak, is there any place that I should look first?

Anyhoo, you guys with all the knowledge let me know. I'm going searching for vacuum leaks this weekend since I usually replace most of the vac lines on my older vehicles anyway. Thanks in advance for any help.

 

The trans issue is not due to vacuum because vacuum is not used to control the trans.

When was the fluid last flushed? (How many miles on the car?) If you don't know or it's been more than 50k miles, start with a flush.

 

@VTbricked, well said. make sure you have enough transmission fluid in it. l had the same car and with the same problem. l runed my car for almost 6 months with noo transmission fluid.not even a bit.l didnt know l had no fluid in it and had the same symptoms you are experiencing now. l went over to walmart for an oil change and they told me l had no fluid in my transmission. they added the wrong fluid into my transmission and the jerking and late engagement stopped. with the wrong fluid running in the transmission, it started slipping like crazy after a few months. too bad l knew nothing about cars. check fluid level and make sure its changed if it looks black.

 

161,690 miles. No maint history. Because of that I already changed the timing belt, water pump, tensioner and rollers. Also changed serp belt, fixed horn and odo.

It's got plenty of trans fluid. I had a trans flush already in the works for this weekend. Thanks for the info on the trans pertaining to it not using vacuum, that rules out that question.

 

Yea, change the fluid, especially if it's blackish. Then, you should do it every 10k if it's blackish, 25k at the most.

 

if you flushed the tranny fluid, what kind of fluid did you use.using the wrong type of fluid can be a problem

 

Flushed the trans today. Used what the Haynes manual suggested. It was a dark burgundy coming out and was bright red when I finished. Still has the jerk though. Here's the next question. On the low end there's changing the fluid. On the extreme end there's replacing the trans. What are some of the things in the middle that I can check? I haven't found anything on a couple forums that cover's anything else besides flushing or replacing. To be sure that's not the only 2 options. Thanks in advance for any info.

 

what kind of fluid did you replace the old one with? is the check engine light on or is the flashing arrow showing?

 

The manual likely said DEX III and they don't make it anymore so the question is: What exactly was the type of fluid you used ?? You should have used a "Dex/Merc" but there are better fluids that would work also. I'd be a little concerned if you used a +4 since it's a Chrysler fluid and I have no idea how it would react in our AW50-42 transmission.

One of the things you can try is an additive. I'd recommend trying Lucas. If it doesn't work to cure your jerk it's likely something someone would have to go in and fix and or replace.

 

I appreciate the concern on which fluid I used but I assure you I used the correct fluid. No check engine lights or arrow. The original question wasn't about whether I can pick out the correct fluid, it was, besides fluid and replacing the trans, what other things can be checked.
And by the way you can still get Dex III at Advance Auto.

 

Unless you managed to find a store that still had Dexron-III from back in 2006 you didn't see Dex 3 since they discontinued it back then. I could be wrong, but I haven't seen it on any auto parts store shelves in many years.
I do know transmissions and I was only trying to help. At least one other member who also cared enough to answer your thread also questioned what you used since it does matter.

Dexron-III

In 1993, GM released new Dexron-III fluid. It is generally backward-compatible with transmissions originally filled with earlier Dexron fluids or with Type-A/Suffix-A fluid.

Dexron-VI

The fluid specification for Dexron-VI was introduced in 2005,and was first used as the GM factory-fill automatic transmission fluid for model year 2006. All Dexron-III licenses expired permanently at the end of 2006, and GM now supports only Dexron-VI fluids for use in their automatic transmissions.[3] Fluids asserted by their manufacturers to meet Dexron-III standards continue to be sold under abbreviated names such as Dex/Merc, but the licensing system no longer exists. These fluids are not regulated by GM.[citation needed] Dexron VI is of a slightly lighter viscosity than the prior Dexron fluids. The intent of this lighter viscosity is to gain an incremental improvement in fuel economy by lessening parasitic drag in the transmission.


If the new fluid doesn't work to smooth out the jerking I would try a conditioner. The new fluid with it's detergents or the additive might be able to break down and clean up any varnish or sludge that might be making a solenoid stick. Lucas makes a very good product and if the jerking you are having in both taking off and on the downshift is caused by a sticking solenoid it just may cure it. If not than you might have to go in or have someone replace the shift solenoid for you. That shift solenoid is my best guess at what could be causing your problem. In your case it would be solenoid A or 1. You could also take it to a transmission shop and see if they will do a free diagnosis on it, some do.


To replace you need to remove the battery and battery mount plate. Remove the upper tranny to radiator hose at both ends, ; remove the dipstick housing and loosen the bracket on the left side of the solenoid cover and allow it to rotate down ( I think it is there to **** off anyone attempting to do this job ). The solenoids are under the black cover forward of and below the PNP Switch. It is secured with 9 #40 Torx Bolts and they are Loctited in. For the one just up from the bottom, you will need a 1/4 in. drive Torx bit and to reinstall it you will need to glue the bolt to the bit to get it started (possibly removing the gold covered cover to the left of the solenoid cover could negate this need).

You will need to elevate the tranny a couple of inches to access the right lower bolt (use a floor jack and a piece of 2x4 under the trans housing - no need to unbolt any mounts).

You will need a relatively short 1/4 extension to get at the difficult bolt mentioned above.

Once the cover is off, replacing the solenoids/s is very easy - the recepticales are color coded on the solenoids and the solenoids are pictured by location in the manual available for download on this site.

The cover uses RTV sealant and you will lose approximately 2.5 quarts of trans fluid during the operation.

Reassembly is opposite dis assembly and relatively easy (the Loctite is the worst part as the Torx Bolts have relatively shallow depressions and are somewhat difficult to get a good hold on with the limited access afforded due to the sub frame.

 

Thanks for all the useful info. I appreciate the help believe me. I've used the Lucas stuff before, it seems to help. I bought the Dex III at Advance auto in Culpeper, VA just this past weekend. I'm sorry you're having trouble finding it but I've been getting it for the last couple years. New, not dated 2006. I'll check into the shift solenoid dealio and see what I can find.

 

I'm not having any trouble finding it because I use a newer, better fluid in my older GMs that spec DEXRON-IIIŽ. If you notice that registered trademark at the end of the name you will notice you will not find it anywhere for sale. They abbreviate the name because they can't legally call it DEXRON-IIIŽ because it's no longer licensed to be manufactured.

In my volvo I'm using a specific Ford fluid because it firms the shifts and doesn't allow the clutches to slip as much as DEXRON-IIIŽ or Dex/Mercon will.
You didn't buy DEXRON-IIIŽ, they don't make it anymore. That's as clear as I can be. You purchased what is know as "Dex/Merc" and it is backward compatable to DEXRON-IIIŽ but it isn't DEXRON-IIIŽ. If you still have a doubt, read the label Advance puts on it.

• Formulated for older model Ford and General Motors vehicles
• Suitable for transmissions requiring MERCONŽ, DEXRON-IŽ, DEXRON-IIŽ and DEXRON-IIIŽ automatic transmission fluid

They are saying it is "suitable" for transmissions that required DEXRON-IIIŽ and those others. They are not saying anywhere on the front or back of the label or on their website it is DEXRON-IIIŽ.
You wanted someone to answer your question who knew transmissions. I know, I'm trying to inform you and I'm using fact. Calling Dex/Merc DEXRON-IIIŽ is like calling a facial tissue a KleenexŽ. It's not exactly accurate but we know what you're saying and it's an accepted noun for an item that does the same function
I do see it's a bit misleading because they call their Dex/Merc "Dex III/M" but like the facial tissue, it still gets the job done and yes you did use the correct fluid and finding out if you did was the main goal in the first place.

The reason the fluid is important is if you used the wrong fluid you could have a second problem and either make the first one worse or have more going one. It's like replacing a bad part with a new bad part. It's new so you trust it and move on everywhere else because it's new so it couldn't be bad. Doesn't happen very often but it can eat you alive in time because you're chasing everything else.

How's it shifting now ??