Hey all, I don't think that my overdrive is working correctly. It seems that the transmission has to warm up before it works or you need to go about 50-55 mph for it to shift into its final gear. Would the transmission fluid need to be changed?

 

thats the first thing I would do..a full flush of the transmission. if that doesnt fix it, next step woudl be to pull the OD solenoid and see if its gummed up or there's any flug in the whole that it goes into (yes, this requires draining the tranny fluid again). if THAT doesn't fix it, time to drop the pan and clean and inspect all the control valves, this is a job for a transmission shop unless you really know what you're doing (and if you had this level of skill, you wouldn't have asked the above question .

 

Are you certain of the upshift speed? I think the lowest I have had an AW71 shift into OD was 43 mph and that's with almost no pressure on the gas. Accelerating with any degree of briskness would, IMO, have a normal shift of 50-55. But, that's not to say the fluid and filter don't need to be changed.

 

my 92 740 turbo wagon will shift into OD at like 35 if I'm just cruising along... even gentle acceleration at 40-ish will stay in OD, until I give it a bit more gas, THEN it shifts out.

is my shift cable too slack? I dunno, it seems to work fine to me.

 

Think I would just check the solenoid as I was changing the fluid.

 

yeah, probably (re checking solenoid while flushing). I've heard people report they found flug in the bottom of the hole that the solenoid threads into.... not sure how I'd extract that, maybe flush it out with a bit of spray cleaner and/or suck it out with a mity-vac ?

note that flushing the tranny requires more than just draining it. pulling the plug will only drain about 2/3rds of whats in there, the torque converter holds another quart and a half or so.

warm up the transmission by taking a drive, let it cool some so its just warm and not HOT, then pull the drain plug, and drain whatever comes out into a clean measuring container, then replace the plug and refill the tranny with the same amount as came out... then to complete the draining, you disconnect the top hose to the transmission cooler at the radiator, and stick that into a waste container, run the engine til you get a quart out, add a fresh quart in via a funnel on the tranny dipstick pipe, repeat til the fluid runs clear. it could take as much as 12 quarts of fluid to fully flush it.

 

Now, before i change the fluid, it would be nice to know where the solenoid is located on the transmission so I can check it. I hope there is at least a diagram for it because I don't see anything realating to it in Chiltons repair book and I learn better visually.

 

i believe its on the left side, on top of the 'flange' thats on the bottom of the transmission, held on by two bolts from above. I'm pretty sure its the only thing *on* the transmission with a wire coming off it.

here. part #46.


click for bigger

 

Thanks pierce. Now, if I read correctly I am able to get a Automatic Over-Drive Solenoid Bypass Kit from IPD for $40, plus shipping. Would that also be an improvement for the transmission?

 

that bypass kit replaces the solenoid with a plate. if your OD is slow to shift, that probably won't fix it. the kit is meant to bypass the solenoid when the electrical control system is hosed (its really hard to fix the pushbutton on the shifter, or the wiring in the shifter stalk, which is one common failure mode).

I still think flushing the transmission and giving it fresh ATF will very likely fix this.

 

OK, thanks. Now if only my printer worked.

 

Tis a sad day for me. While draining the fluid for the transmission, I have found that water has gotten in the transmission and transmission fluid into the coolant. Now I need to find a replacement transmission and radiator, unless you guys know something that I don't.

 

well, if you cruise pik-n-pulls, be aware that 92+ used a different larger radiator, and electric fans rather than belt driven. bunch of other changes, including turbo air plumbing, so I'd stick with loooking for a 1991 or earlier.

the tranny should be compatible between any AW71 turbo 740/760/940 (there WAS a different ZF tranny used on some cars, these had a shifter that said 1,2,3,D instead of 1,2,D plus the OD button. the ZF tranny is weaker than the AW).

 

Yeah, I know this place in Atlanta where i can get parts from. If I take the transmission and the radiator to the parts place then I can match them accurately and exactly.

 

Next question, would I be able to do a complete transmission flush and save me not buying another transmission. Mine still shifts gears very well. Would that help? I know that I need to replace the radiator hands down.

 

a tranny flush isn't hard to do (once you fix the radiator).

I'm wondering if it wouldn't be a bad idea to flush it in something water mixable like an alcohol to remove the moisture... but you'd need to get ALL traces of that out before using it again, which is problematic, so thats probably NOT a good idea.

Basic procedure for a standard thorough ATF flush... buy a WHOLE lot of ATF, dex/merc type. 12 or 16 quarts even. get a clean tranny funnel (something that fits into the tranny dipstick tube) get some transparent gallon+ containers that have marks for volume.

warm the transmission up thoroughly via driving. pull the plug from the bottom, and drain into a graduated container, you'll get 3 or 4 quarts out, I believe. let it dribble for quite a long time. replace the plug, and add as much fresh ATF via the funnel as came out. disconnect the upper transmission cooler hose at the radiator, and run it into a graduated jug. start the engine, let it idle until 1 quart comes out of that hose. stop the engine, replace that quart with fresh ATF via the funnel.. repeat until it comes out clean. replace the hose, drive the car a few miles to warm up the tranmission, and with it idling, check the ATF level at the dipstick, top it off if necessary.

since you had water in there, I'd consider doing this a couple times, a week or two apart, figuring the heat of operation will help boil out the water. if you want to use a premium/expensive ATF like a Castrol synthetic, wait til the LAST change, as that stuff is like $8/quart.

 

Ok, I just got myself a new radiator. Now, the way that my father was thinking was that we take a new pump bug sprayer and fil it with cheap ATF fluid and just pump till clean fluid comes out while the ignition is on, but the engine off while shifting through the gears. Do this 2-3 times over a couple of weeks and also add some sea foam that is made for the transmission to take out the left over water.

 

i think you'll want the transmission warmed up and spinning to do that, as there's a quart or two thats trapped in the torque converter, and if the engine is spinning (in neutral), that will pump itself out the upper cooler hose.

yeah, doing the initial phase of the flush with seafoam is probably a good idea,

 

OK, i gave up on the idea fo me doing the purging by myself, soI am getting a professional to do it for me, just need to drop the pan for him and he'll do the rest. My only problem is that the dip stick tube is not coming off the pan no matter what I do, even after a overnight soak in kroil. Should I put a torch to it to heat it up so that it may get lose and is it reverse threaded?

 

Ok, disregard the last one. Got the pan off and am going to get it purged.