speedometer not working

[Ken]

Is the speedometer gear that goes into the transmission the same between the R154 and W58?


I converted my Cressida to a 5-speed (W58) and used an R154 speedometer gear in the transmission. Now the speedometer doesn't work. I don't think it's the cable, because the needle spins when turned manually from the other side. I tested the gear too and that's fine.

Any input is appreciated.

 

[CRE]

The R154 uses a smaller diameter drive gear. It won't work in a W58.

 

[Ken]

thanks man, i had a feeling they were different.

 

[CRE]

Yeah, the diameter's a few mm too small... ask me how I found out.

I've been meaning to contact the people at Marlin Crawler to ask if there a speedo drive gear for another W58 with the right tooth count for my 3.91 diff. For the time being I recalibrated my speedo, but that leaves the odometer and trip reporting shy by about 10%.

What diff ratio do you have?

 

[Ken]

how did you find out? lol, I have no clue what diff ratio I have, maybe you can tell me. It's a '90 model. Did MX83 Cressidas come with different rear ends?

 

[CRE]

I'm not sure what diff Cressidas came with. Check the chassis ID plate for the differential code. It'll be something along the lines of G284.

Here's the breakdown of the diff codes (these pertain to the MKIII and may not match yours):

G = 8.0" Rear End

28 = 4.30:1
30 = 3.73:1
31 = 3.91:1

4 = 4-pinion, Non-LSD
5 = 4-pinion, w/LSD

Here's a full listing with a picture showing the plate and where the code is.

 

[Ken]

wow, excellent info. I'll take a look and see what it is. thanks again.

 

[Ken]

ok, so i double checked the speedometer cable and gear and verified that they're working, but the speedo still doesn't work.


I removed my gauge cluster, and the needle doesn't even spin while driving. what could be causing this? I am using the correct W58 speedo gear btw.

 

[CRE]

It's slipping somewhere. How'd you verify it's all working? There's a big difference to spinning the speedo cable by hand (not enough pressure to cause fracture in the line to loose it's grip completely) or testing it with a drill and having someone check from inside.

I presume the speedo is known to be good?

hmm... Is the cable the stocker? Or did you replace it? Check for and hard angles which could be causing the cable to bind up. Did you have to move the cable to a different location from where the stock drive gear was?


EDIT: One more thing. If you look at the bottom of the speedometer's face there will be a legend. The MKIII's speedo is set for "1026REV=1MILE", so for every 1026 revolutions of the cable the odometer reports 1 mile... you need to spin the cable alot before you'll see the speedo move, you might want to keep an eye on the tripmeter while troubleshooting this way.

EDIT2: One more thing to check is that there are no signs on excessive wear on the spline and shaft of either the sending gear or the mating end of the speedo cable. I believe both should be nice and square shaped (about 3mm) check for stripping or rounding off of either.

 

[Ken]

well, I jacked up the rear of the car, removed the cable from the transmission, and put the transmission in gear with the engine running to get the wheels moving. The speedo gear doesn't even turn when the wheels are moving.

Before the swap, the speedometer was working fine, and the cable worked fine in my Supra before I removed it. I'll try to test with a drill and see. Thanks for your help, I really appreciate it. :icon_bigg

 

[Ken]

ok, I tested the cable with a drill, and it's definitely good. also, the teeth on the speedo gear all look to be intact; no stripping.


So I guess that leaves the part inside the transmission. What would be the best way to check it?

 

[CRE]

Did you compare the size of the nylon drive gear you thing is a W58 gear to the R154 gear? It's possible it's another R154 or perhaps just worn down. Measure the diameter of the gear and check it against the known R154 gear. There should also be a number on top of the nylon gear, on the R154 gear I have sitting in front of me it's "10 32". What's the number on the one you have currently installed?

ok, I tested the cable with a drill, and it's definitely good. also, the teeth on the speedo gear all look to be intact; no stripping.


So I guess that leaves the part inside the transmission. What would be the best way to check it?

Well, that's a tough one... IIRC, the speedo drive gear connects to a worm gear inside the tranny. I can't really think of a very safe way to test it apart from taking the transmission apart.

I suppose you could put the rear up on jackstands (with blocks on both sides of both front tires), drain the gear oil, start the car, put it in gear and look into the sender's housing hole (preferably from the side of the car with a flashlight and mirror and NOT from under the car) to see if it's moving. I DON'T recommend testing anything on a car while it's running and in gear.

(Disclaimer) If you do this you do it at YOUR OWN RISK, neither I, SM or anyone on SM will accept any responsibility should something go wrong. (/Disclaimer)

 

[Ken]

yeah, I compared the W58 gear with the R154 gear and they are different in size.

The worm gear inside the trans spins along with the output shaft, and the teeth don't feel worn down or stripped. But, the worm gear is able to slide back and forth (towards the front and rear of the car). I don't think that's normal, as the worm gear on my R154 stays put when I try to move it back and forth.


What I am thinking is that the worm gear is being slid to where it doesn't mesh with the speedo gear upon installation. So as of right now I'm in the process of removing the extension housing to see what is going on in there. Too much work! :nono:


I'll take some pics when the housing is out.

 

[CRE]

That really sucks. I hope it's nothing too bad.

 

[SupraDerk]

On the long cable, the part that connects to the drive gear... there's a little gold "key" on the end. Check to make sure that that's good and tight on the end of the cable.

One day I was driving my car and all the sudden the speedo stopped working. I checked and quadruple checked everything and nothing was wrong. I even drove the car around the neighborhood without the gauge cluster in and the cable wasn't moving. Then I realized that that "key" wasn't tight on the cable...so I got some epoxy welder... put it between the "key" and the cable, let it sit... then BINGO. Working speedo again.

 

[Ken]

yeah, i did that. on top of that, i jacked the car up and put the car in gear with the engine running. I removed the speedo cable that screws into the trans so I could have a look at the little cylinder in the speedo gear housing, and it doesn't spin when the wheels are moving.


It's strange, I even removed the extension housing and the speedo gear on the output shaft looks intact and secure. I'm just going to swap in a good known working W58 in. The clutch was starting to slip anyway, so I'll go ahead and take care of all that.

 

[Ken]

so I swapped the transmission out and the speedometer now works. go figure. at least I know how fast I'm going.