HI! I'm new to the forum though I have read many post on here, I'm experiencing a odd issue, and any help is appreciated! My speedo works fine when I start driving, after 10-15min on the road, the speed gradually drops to 0 with the car moving normal speed. If I stop and let the car cool off, it will work again for another 10-15min. Also it knocks out the OD, and or cruise control when it drops off! (Gage cluster was rebuild not long ago, no change in issue) Car is a 1988 with the DNE 4+3

 

Does check light come on when speedo quits?

 

No cel, only thing not working is the speedo! Everything else is normal. No other issues at all. It does seem to be heat related, making that assumption based on it doesn't happen until the car warms up good, and will start working normally after car cools off,

 

no ses or codes means ecm getting speed signal from transmission. I think problem is in cluster.

 

I had the cluster rebuild! That didn't change anything. Also tried a cluster out of another car, exactly the same! Can't imagine 2 clusters having the exact same issue, plus both clusters work fine in the other car! To me that rules out the cluster!
Thats why I posted the question! I'm scratching my head on this one! 1st time I ever saw this issue! And if it was the speed sensor, they are almost impossible to find a replacement, short of buying a used 4+3 for parts.

 

How long have you had this car? Did the speedo/odo ever function correctly for an extended period of time - months or thousands of miles? My experience with the earlier VSS is it either works or it doesn't.

Have "YOU" ever serviced any aspect of the 4+ OD in this car?

Is the car stock in most aspects? Tires wheels etc?

The "cluster" is the 1st stop!!! OP's problem is NOT cluster related.

 

Got the car last fall, and it came when this problem and a bunch more (most have been fixed), it looks and runs great too! Previous owner just couldn't get all the bugs out! 1st thing I did was replace the cluster due to bad power supply! Only service to trany I know of is clean & fluid when the motor was rebuild, and I just did a filter a week ago. Only thing stock on the whole car is the trans & rear end, engine is .30 pistons, cam, intake mods, headers, duals, most of the smog stuff removed, wheels C5 18r 17f, and not that it matters a complete aftermarket 91 body kit!

 

Seeing that it "came with" I'd maybe check a couple of things. I'd remove the VSS and inspect the gears (because it's the least expensive 1st move). I'd want to see a red drive gear and maybe a green driven on the VSS. The condition of the teeth is what you're looking to confirm, I'd also rotate the drive-shaft and make sure that the clip retaining the drive gear is in place. I would look on the VSS and confirm that it's correct for a 40+ tooth count. If the VSS is stock it will have a "center" electrical connection. The VSS in that vicinity will either have 40 - 45 or 35 - 39 molded into it. If the VSS isn't "center" electrical then it's not stock.

I'd maybe buy this VSS and a connector so that if everything looked OK in the transmission and the tooth count matched what I suggested. This would make it maybe a "once and done" operation.

Take this GM part # to the parts supplier of your choice and use it to cross-reference the brand stocked.

GM# 10456089 VSS and buy the appropriate connector to match. nearly all auto parts vendors should be able to help you.

If you find other than red/green plan on maybe a return of the VSS .. SO .... buy "LOCAL". LOCAL ALWAYS ........

*** All of this is assuming you've confirmed the condition of the VSS connector and the condition of the YELLOW/PURPLE all the way to the conduit where it's directed towards the cabin. You say also that it happens "always"! Yes to always or maybe just intermittently?

 

Thx WVZR1, I will check that! I'll admit since the problem happens almost like clockwork bet. 10-15min driving, never erratic, never intermittent, and when it drops out it is very even and consistent, (from like 70-64-57-42-36-0 no pattern) l had ruled out a gear issue! And since I was given p#25007339 by a Chevy stealer, which I was also told was no longer available, and the fact that I already trying swapping clusters, I was hoping it was something else I missed! From asking around at a few local Vette shops and a few good mechanics I know, it is a very unique problem! I am now hoping for someone who has seen and solved it!

 

10456089 comes up as the VSS for 91+, will this work on a 88 4+3? If so this is good to know!

 

You've tried multiple VSS? How many? What is a "Chevy stealer"? What lead you to rule out the gear? You've actually inspected everything that I mentioned? Why do you believe you can rule out the gear issue?

 

Re-reading you bought this car with issues. This concern came with car. Any mods do you have FSM? If you go to BATEE.com there is info on cluster including wiring diagram. Cluster controls cruise control. Basically VSS sends analog signal to cluster. Cluster sends buffered signal to ECM. ECM should sent DTC 24 if VSS is (0 mph) less than expected compared to other engine sensors for 3 sec so if tach is is reading 1500 and tps is 1.0v code should set. If you have access to scanner does ecm read 0 mph when condition happens. IDK if ecm could cause this but it is on the other end of the circuit. You could remove terminal for VSS temporarily from ecm connector and see what happens. you should get a ses light light but speedo may keep working.

 

WVZR1...You completely missed what I was saying! No! I have not changed the VSS, because I can't find one! Chevy stealer=Chevy Dealer! the place that likes to take your money for over priced parts! and I assumed it was Not a gear issue because of the consistent pattern that it works (and stops working) My previous experience with gears is the problem is usually erratic, or intermittent, or not working at all!
The only thing ruled out is the cluster! (car cam with issue, tried cluster out of another car, no change! had cluster rebuilt, no change, tried my cluster in another car, worked fine)
Kevova... Yes I have the FSM! and BATEE is who rebuilt my cluster! I have even spoken with him on the issue, He did not have a answer either!

 

Op - I didn't think you had but then you started to comment and it became vague. I offered you up a solution and if you want to do a VSS it can be done BUT I'd do a visual maybe first and check information on the VSS that's in the car. Is it white or black, 35 - 39 or 40 - 45 molded onto the VSS and is it a "center Weather-Pack" take-off for the electrical?

 

Update to my faithful helpers...I removed and inspected the VSS it is a black center connected stamped (40-45) red drive gear, Green driven gear on the VSS, and everything looks clean! also now I have code 24 from the computer, But NO CEL on! since the battery had been disconnected so many times for other work, likely I erased the code before I realized I had one!
Now to the VSS...I was given GM P# 25007339 by my local Chevy Dealer which is No longer available!!! I have tried without success to find one!
Does anyone have a alternate part number or know of a different VSS that will work with the 4+3 ???

 

With the gear combination that you've mentioned the VSS that I mentioned several posts ago will do what you need. The VSS and the connector. I'll try to post back as to how to pin it. The only one I have is in a transmission in a crate. I likely have 1 used correct center connector VSS but I can't put my hands on it.

Pay the extra for a GM/ACD connector 12085498/PT120 as I believe that the GM/ACD connector will be marked A - B or maybe just A. You want YELLOW to A and PURPLE to B I believe. If someone has a '91+ M6 or a '91 - '93 A4 maybe they could confirm my thoughts.

In this drawing I believe the terminal that's identified dimensionally is A:

http://www.wellsve.com/custom_search...ngs/SU1005.pdf

 

I checked vss part # came up with 2 different ones 25007224 and 25007308 depending on axle ratio. If you post axle ratio someone with be able to tell you with one.
If you search 25007224 ebay shows one. Kit comes with jumper to adapter connector. If you know tooth of driven gear count you should be able to find sensor you need. The connector style change to a unique type only used for VSS.

 

OP has a 3.07 with the 4+ transmission, he mentioned red/green (17/42) which I had acknowledged. He also confirmed the 40 - 45 on the VSS. The 25007308 was the last production number for what the OP mentioned looking (25007339) for. I sold the last couple NOS that I had in the past 18 months. If the OP actually has a VSS issue the solution I suggested would be my first move, certainly the least expensive attempt.

 

A 10456089 with the correct connector should work. 10456089 is still available form GM and aftermarket equivalents.

 

You wont necessarily get a check engine light because the computer doesn't know that the car hasn't actually stopped. A damaged gear issue doesn't make sense to me since damaged mechanical parts don't really cause intermittent conditions. I don't believe the cruise will malfunction if the cluster is messed up. The first place I would be looking is the vss itself.