94 Ranger XL -Instructions on how to replace a vacuum modulator.

Hi. I've owned a 1994 Ford Ranger XL :rangergreen: for about a year now and put on over 10k miles since then, but have a transmission FLUID problem.

The engine is a v-4 with 8 spark plugs, and an automatic transmission. There are 195,000 miles on it.

PROBLEM: After the engine warms and I accelerate after coasting or idle, the exhaust blows large clowds of transmission fluid SMOKE. It will also burn transmission fluid (through the engine) when acceleration AFTER a heavy incline or stress on the transmission. There is also a "RATTLE" from the motor during these periods.

Mostly the problem occurs when driving at higher speeds (55 to 70 MPH) and then dropping down to 30 MPH with a slight acceleration. Then there will be the "rattle" followed by large puffs of transmission fluid smoke through the exhaust.

How much transmission fluid burns through the exhaust? A 150 mile trip through steep hills will burn 1 quart of fluid.

QUESTIONS:
Is the problem the transmission, the engine, or both?
Is it worth fixing, or should I just get another engine and transmission?

Any suggestions will be helpful and appreciated. Thank you!

Welcome to this forum! It sounds like you need a new vacuum modulator. Check the vacuum line for signs of leaking transmission fluid.

Vacuum Modulator

BrooklynBay said:

Welcome to this forum! It sounds like you need a new vacuum modulator. Check the vacuum line for signs of leaking transmission fluid.

Click to expand...

Thank you BrooklynBay.

I'll try and find the Modulator. However, this is not an external leakage problem. The transmission fluid is somehow getting into the engine's combustion chamber and burning off.

Are you suggesting that the Vacuum Modulator could cause this specific type of problem?

Is the Vacuum Modulator the round component located on the drivers side of the engine with 3 or 4 vacuum lines coming/going to it?

How would I test to see it that is bad? Transmission fluid on the inside of it?

Thank you so much.

Tom C.

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-- Edit --

Well, I believe you are exactly correct. I just searched "1994 Ford Ranger Vacuum Modulator" and the first search result pointed me to another forum describing the SECOND problem I was about to post about -- how transmission fluid gets into the oil, and how is it that the oil fluid levels keep rising (having to drain some off every month or so).

The poster also said that you may need to lower the transmission, remove the cross member bar, and the modulator will be on the top of the transmission.

Can you confirm this? Any tips?

Thyank you again.

The modulator is on the passenger's side of the transmission to the rear of the 2 servos. It has only one vacuum line connected to the engine. Transmission fluid will get drawn into the engine if this part has an internal leak. There are 2 ways to get to this part. One way is to get to it from the bottom. You have to remove the catalytic converter. The next way is to get to it from the top from the hump area. You have to remove the front seats, and pull back the carpet. There is an access panel that was originally designed to enable access to a manual transmission. Let me know if you have trouble finding this part. I could suggest a few places to get it or I have several on hand as spare parts.

Vacuum Modulator Brands

Follow Up:
Thank you. I crawled under the truck and located the vacuum line that extends from the transmission Vacuum Modulator up to the engine's intake manifold. The vacuum modulator was located on the transmission exactly where you said it would be (behind the 2 servos on the passenger side). With the vehicle not running, at the manifold intake, I removed the vacuum tube and swabbed the interrior of it with a q-tip. I did see some transmission fluid on the swab but not much. However, I'm going to presume this is the problem and within the next few days try and see which way will be the best access to changing it.

Question:
I located a transmission vacuum modulator online. The brand is by "FRAM". Would you recommend this brand?

Thank you.

Yes, it's good. That's the same brand that I keep for spare parts.

Vacuum Modulator access

Thanks BrooklynBay. I must admit you're very experienced and knowledgeable on this type of issue.

I've looked at both options to access the transmission vacuum modulator-- from inside the cab, or underneath. I believe my easiest option is from inside the cab.

Underneath, I'd have to cut out the exhaust pipes, in addition to buying the tools to do that. However, withinin the cab, I have 60/40 bucket seats. Each seat is fastened to the cab floor with only 4 bolts, 1/2" head, and are easily accessable. Simple task of removing the seats and pulling back the carpet, opening the access panel on the hump, and then gaining access to the part from the top of the transmission.

I'll order the part on Monday. When I get it installed (or run into problems!) and take it for a test drive, I'll post another follow up with results.

Thank you again.

Tom C.

There is a pin behind the modulator that could easily fall out, so be very careful when you remove the modulator. Hold a magnet underneath the modulator while you are pulling it out. Always remove the modulator with a twisting motion instead of just pulling it out. The O ring holds it in place along with a bolt, so the new modulator should have a little transmission fluid applied to the new O ring to make it slide in easier. Apply Vaseline (petroleum jelly) onto the pin, then insert it into the new modulator. It will help prevent it from getting lost. Use a small wire tube brush to clean the bore of old debris before installing the new modulator. There are numerous complaints from people explaining that they are having shifting issues with the new part because dirt was stuck to the bore, and is causing the pin to bind. Are you getting a preadjusted modulator or an adjustable one? Which place are you ordering it from? How is your heat shield? Some people replace the servos at the same time since they are accessible.

Thank you. Job Complete!

Hi BrooklynBay. Job complete!

Before describing my installation and testing steps, I need to say that without your advice and guidance I could have never done this. The truck now runs AWESOME! Better than it ever has.

This morning I called several local auto parts dealers (Advance Auto, NAPA, and Federated) and not one had the part (transmission vacuum modulator). I ended up calling a transmission shop located 20 miles away, and BINGO, they had it (cost = about $20). I wanted a preadjusted modulator, but all they has was an adjustable one, which was not a problem! I then began the task of attempting access to the upper-transmission via the cab interior.

I removed the two seats from the cab interior. Each seat is fastened to the floor with four bolts. --> caution, the bolts need to be backed out slowly, as the head snapped off one of them. I then pealed back the carpet (front to back) allowing me plenty of working space with the access panel on the hump. Removing the panel is easy, having only four screws with 3/16" heads. The clips on these were rusted from the bottom.

Opening the hump access panel revealed the top of the transmission. The heat shield was not an issue and didn't have to be moved or removed. I had just enough access to the vacuum modulator, allowing me to get both hands down beside the transmission. I removed the vacuum line first (and transmission fluid was evident and plenty present), then removed the retention clip and bolt (bolt was a 10 mm head). I did as you suggested and slowly twisted the modulator side to side, and gently out. The pin was just laying inside of the modulator. I lifted the modulator out with the pin facing up to prevent losing it.

Installing the new vacuum modulator was a piece of cake. I just followed your recommendations, and it went in without a problem.

Prior to connecting the vacuum line to the vacuum modulator, I started the engine to pull through any remaining transmission fluid that was still in the vacuum line. I left the engine run for about 60 seconds.

I then connected the vacuum line and took it for a test drive. I couldn't believe the difference. My little truck hasn't run this well ever. Now, there is no smoke blowing out of the exhaust, no rattle in the engine, and lots more power. Also, I didn't have to make any adjustments to the adjustable vacuum modulator -- I just left it as the manufacturer had it. It was PERFECT.

I ran a bead of silicone around the hump access cover to prevent water from coming in (the bolt clips on three of them were rusted and were not usable), placed the carpet back down, and installed the seats. The one bolt that snapped off I left, drilled a new hole, and fastened the seat frame to the floor using a large sheet metal screw.

Then, I celebrated with an ice cold beer, and pat on the back.

THANK YOU BrooklynBay! Fantastic advice.

Thanks for the update! Did you take any pictures as you were doing this? It would make a great step by step how to for people not familar with this type of repair.

Photos

Unfortunately, I didn't take any photographs. Now I wish I had, as it would have been very easy to do so and would have enhanced the removal and installation process descriptions.

If there is anything that I could do to help others with this type of repair, I would be glad to help. I'm not a mechanic, and this was a wonderful experience for someone like me (inexperienced) who has never done any work on or near a transmission. This job has given me additional confidence to do other projects that I'm not experienced in. And with those, I will again seek advice before attempting the work.

The best advice I could offer to someone who has never done this type of repair would be to follow instructions and take your time. The steps and advice that BrooklynBay has given are precise, exact, and should be followed to the "T". Had I not followed the recommendations as given, this repair job would have NOT been possible as easily as it really is.

Thank you BrooklynBay and the hosts of this Forum. Please keep up the excellent work.

I've renamed this thread, and added it to # 56 in my list of useful threads.

Hello.

I to, believe I have a vacuum modulator problem. I have a 1992 Ford Explorer, Eddie Bauer edition. It's worked fine up until I left from work one morning. I can put it in every gear, and they all work except drive and over drive. Once it's in drive it acts like it's in first gear, and doesn't shift up gears, just keeps raising those RPM's. However, I can shift it in second, and it will go up to about 40-45 like it's suppost to, then shift up to drive, and it'll do nothing. Still in second it seems, even if I switch from OD to D. It feels like it did something, but doesn't shift up still. Reverse works also. Someone at work said it's most likely my vacuum modulator. And after reading this forum and other searches from google, I to believe that's the case.

I'm going to attempt to replace it myself, following all the instructions I've gathered here and elsewhere. I went outside to just try and see if I can locate it, but I couldn't see anything for the exhaust pipes, plus it is raining, so I'll have to wait. I called around to a few auto parts stores and one has the kit I need for $21.

I will keep posted on my progress, or how it goes. I will even try to take some pictures of the steps I take. Wish me luck!

Tein said:

Hello.

I to, believe I have a vacuum modulator problem. I have a 1992 Ford Explorer, Eddie Bauer edition. It's worked fine up until I left from work one morning. I can put it in every gear, and they all work except drive and over drive. Once it's in drive it acts like it's in first gear, and doesn't shift up gears, just keeps raising those RPM's. However, I can shift it in second, and it will go up to about 40-45 like it's suppost to, then shift up to drive, and it'll do nothing. Still in second it seems, even if I switch from OD to D. It feels like it did something, but doesn't shift up still. Reverse works also. Someone at work said it's most likely my vacuum modulator. And after reading this forum and other searches from google, I to believe that's the case.

I'm going to attempt to replace it myself, following all the instructions I've gathered here and elsewhere. I went outside to just try and see if I can locate it, but I couldn't see anything for the exhaust pipes, plus it is raining, so I'll have to wait. I called around to a few auto parts stores and one has the kit I need for $21.

I will keep posted on my progress, or how it goes. I will even try to take some pictures of the steps I take. Wish me luck!

Click to expand...

Hello again!

I do realize this is a very late posting as a follow up. But as we always say, better late then never.

The good news is. I didn't have to replace the vacuum modulator. In fact, I didn't have to do much at all. I took a look under the tranny that same day and to my surprise, the small pencil size hose connected to the modulator was off from one end. I just wiggled my hand back in the tight space and attached it back. Took it for a test drive to see if that was it, and viola! It was. So just to be sure, I went to Advance and got another hose and replaced it. I suppose the hose just slide off from wear or bumps over the years.

So in closing, if this helps anyone. It could just be due to an air leak or pin hole in a hose or maybe just a lose hose(in my case anyway).

Thanks for the update! Rubber hoses eventually dry out. How are the other hoses in your vehicle?

They look surprisingly good to be a 92. The guy my dad bought it off from didn't drive it very much. It only has close to 86,000 miles on it.

I recently did this and everything was fine for awhile, then first to second shift is delayed, First will go up and slightly over 3000 rpm before the shift. I had drop[ped the pan too and re-dropped it today. The tranny fluid is milky but the radiator shows no sign of tranny fluid. I think the pan drop/filter change at the time of the MV replacement may have caused trash to interfer with the mod valve. I'm thinking about using some trans-x to clean things up, but I'm fearful of losing the tranny completely. Can't afford to lose the truck for at least 3 weeks. Just started a new job and the commute is 37 miles one way. Money is very tight.

Thanks for being here.
Scott

i have had the same issue. i replaced the old modulator with a new adjustable one.. however i'm haveing late shift issues... and issus with it dropping into passing gear.. when i put my foot down it seems to shift into neutral instead of down a gear. when i let off the gas it drops into passing gear. ive tried adjusting it from out to in with no success. and body have any other thoughts? also with the old modulator it shifts fine but burns tranny fluid.

i recently had the same problem with my 94 mazda b4000. i am not a mechanic by any means. i googled my problem and found this thread. thanks to brooklynbay for his knowledge because i was able to change it myself. so to anyone having these issues this is the answer. i changed mine 3 days ago and it took about 100 miles to smooth all that fluid from my systems but it drives better than ever and it fixed numerous issues. thank you brooklynbay your the man!

im tackling this issue tomorrow...Im losing tranny fluid and it looks like its ending up in the engine.....Just bought this thing for cheap and find the engine oil to be overfilled and too dark for 1500 miles. Bought new vac. mod. to put on tomorrow. Engine runs rough and weak for a 4.0- prolly some fouling of spark plugs. Im also getting the occasional smoke cloud out of the tailpipe...now if only i can rig it to do that only on demand! Then i can hide my escape!