High RPM's on hwy 5th gear?!
 

Hi guys. New to the forum but have used the club since 2008 for troubleshooting and advice. Okay, when I'm cruising on the highway at let's say 60mph my tachometer reads at least 3500+ rpm!! I know this isn't normal by any means. The FD doesn't have any aftermarket gears or ring and pinion. I'm not just taking previous owners word on that, I know because I took it on a 700+ mile trip from KY to FL and all was well and drove like my first FD. I first noticed this problem about 3 months ago when driving from work on a long stretch of road. I'even PM'd dale to see if he could help me and he seems equally perplexed. Any information would be a huge help. Thanks in advance guys

Does it also sound like its revving high or just reading high?
FYI you will notice this when the clutch is slipping on the highway, the load is higher in top gear and the engine will rev and the car won't really go faster. At least not like when the clutch is completely clamped to the flywheel.

If it's just reading high RPM then the gauge is fubar.

If you have a power FC with commander you can monitor RPM and compare to your gauge.

My guess is the clutch.

Maybe it has an a J-spec transmission? 5th gear is shorter in it and would read similar RPM at that speed.

If not, probably what ZoomZoom said.

three ideas pop to mind.

the first is a bad tach, i've seen them intermittently read high. although the rest of the time they were either dead or correct, so not quite the usual symptom.
second is a bad clutch. its possible that its slipping in 5th, although i think in an FD you'd notice in other gears.

third is if someone had a different sized tire front and rear, and you rotated them without noticing. i've done this myself.

It's most certainly revving high because that's what initially grabbed my attention. Second turbo still comes on at around 4500rpm. It's like someone snuck in my garage at night and installed an extremely short 5th gear in my FD.

Actually, now that i think about it I'm not even sure if its running the correct rpms in any gear. It's just that 5th gear is so extreme that it's what has my attention.

Unfortunately, I don't have a PFC yet but I was wanted to compare one with my tach just to see. And I also thought that it might have been my clutch so I took the liberty of having a Exedy stage 1 HD clutch kit installed. Eager to see if this solved my delima, I took staight to the hwy (gently I might add) and steadily brought my FD up to hwy speed and it still exhibited the same high rpms.

And after paying $450 for the clutch kit and $413 for the installation for my troubles I received a broken clutch fork:) I would have the only FD going through this.

Nah, not a jspec. It just started showing signs of high rpms about 3+ month ago.

Tach doesn't seem to be broken because the turbos respond at the correct rpms:/

Brand new clutch installed, still breaking it in.

And it couldn't be the tire thing because they are staggered pretty good and that would crazy noticeable! Lol. Thanks tho and keep the ideas coming guys cuz I've been thinking about just putting another tranny in and that would be costly.

If you wanna test with a working tach I think I got a spare one I could sell for cheap, like 25$ shipped.

If I remember right, the j-spec tranny you lose about 200ish RPM, not 1000 like in this scenario.

Worth a shot. What's ur paypal?

any doctor would tell you that you're crazy right now :)

um next step is to verify that the RPM on the tach is correct. the FC has a tach test connector, not sure if the FD does too, but if it does you can hook up any old tach to it and go for a spin.

Sorry 7not8 just checked and my spare one's needle is broken so forget it.

Sorry about the hopes...

It's cool man, no worries.

Maybe it's not 60 ur doing and more like 70 and mph is off

This could very well be the case, it's possible that my whole interment cluster is busted.

My odometer went from working about every other time I turned the ignition to completely not working at all. I used to think it was just not showing the milage on the odometer, once I noted what the milage was before I shut the car off one time. I then drove the car after that with the odometer off, parked it, then the next time I took it for a spin to my surprise the milage was the exact same as it was the last time my odometer was operating properly!:scratch: So, there's no telling exactly how many miles are on my chassis

I'm not gonna mention who I bought my FD from but I will say that I've heard nothing but great things about this seller and was very anxious to purchase my second FD especially from someone who has such a great track record. If I were to make a list of all the things that were not mentioned to me about this car before I bought it then that list would be pretty lengthy. Trust is something that is very important to me and I'm sure most everyone in the 7 community feels the same way, like when we go to the "parts wanted" section and trust that the one we sent a pay pal payment to will send that part to us. I was deployed and handled the transaction by email and my wife went and scooped the car up for me and she parked it in the garage for about 6 months until I returned home, only starting it once a week to keep the car battery from dying. I know that these are old cars and some problems are to be expected like when I bought my first one but I feel like some people will do anything for a dollar.

This post just went a completely different direction than what I intended and I apologize for that but I'm just mad as @$!#!!!! and needed to vent. So, if anyone is reading this and has a decently priced cluster feel free to drop me a pm.

Cluster problems are common on the FD. The tach on my car jumps around and dies sometimes but the speed always read spot on. But now the speedo is reading 10mph faster than what I an actually going. You can either switch to a jdm cluster or have someone repair/replace the capacitors on the cluster. I'll be having mine repaired and will be adjusting the speedo.

Just used a speedo app and tested your theory. My speedometerwas only off 1 mph from what the app said and my RPM's on my tach were around 3700-3800 @ 80mph, which I believe is still about 700 to 800 rpm off of what it should be. Who would be a recommended person to repair my cluster? I can turn a wrench all day but when it comes to electronics I usually steer clear of that due to the fact that I'm color blind unless it's something plug and play like an HID kit or PFC. Thanks

I've found this calculator to be exceptionally useful
Texas Trans Am Service and Restoration - Horsepower Calculators

Assuming stock 225/50/R16 tires (24.86" outer diameter), 65mph would put you around 2600rpm if you have the original 0.719:1 5th gear and a 4.10:1 differential. Probably the clutch slipping as everyone suggested. Just to cover all bases, when's the last time you replaced the fluid and bled the hydraulics?

Thanks for the input. I do have all stock 93 R1 gearing and a 4.10 ring and pinion. I doubt it's my clutch slipping because I just had my clutch upgraded last month and my fluids were drained and replaced with mutol.

A slipping clutch is generally very noticeable and easily tested if unsure. Going full throttle in a part of the RPM band where you make good power will lead to a sudden increase in RPM without any appreciable acceleration.

Given your speedo appears to be working and assuming the clutch doesn't have some oddity it sounds like your trans and/or rear gear isn't what you think it is or your gauge has something wrong with it. For instance, your rpm/mph corresponds well with a jspec 5th gear and/or some other differences. Also, I do not know about FDs but FCs have an adjustment pot on the cluster which can be used for getting a more accurate RPM reading. From your first post though it really sounds like your tach and/or associated wiring/sensor is in need of some TLC.

https://www.rx7club.com/3rd-generati...os-you-984896/

we should clarify, perhaps. there are only two things this could possibly be

1. the rpms are actually high, which would be a slipping clutch, or something.
2. the tach is reading wrong. common in the FD, they go nuts, the ones i have seen are intermittent, so sometimes its normal, and sometimes not. also possible that the speedo is wrong, although i think you'd be able to tell you were going 100mph when everyone else is going 65.... little trivia, the stock gearing with the engine at redline will have you going 190+ mph, which is actually attainable with bolt ons.
3. you're crazy.

You sure you don't have a jdm transmission. I'm pretty sure my rpm is about that range when I'm going 80-85 mph. As for fixing the cluster I was going to find some electronics shop and have them replace and resolder whatever needs fixing.

Hey guys. This whole ordeal has been a huge headache so, I decided to drop the transmission and do some looking around. I've never done this job before in any car but with the help of the search button all things are possible! Lol. So, I drained my transmission fluid to start the job off and I found chunks of metal in my fluid and the fluid itself had a super fine metallic flake to it. After the fluid drained i used my inspection camera to take a peek inside the drain hole and saw a gear that had chips on some of the teeth. More than likely im looking at a bad tranny. Does anyone know where i could get a good one that could be shipped? I hear rebuilding them aint cheap, so buying a used one may fit my budget better. I have the mid pipe, ppf, driveshaft, shifter, starter, and various other
https://cimg5.ibsrv.net/gimg/www.rx7...088d7a07ad.jpg
parts removed right now and will keep the thread updated. Feel free to chime in

Chunky.


https://cimg7.ibsrv.net/gimg/www.rx7...106b8fe77e.jpg


Tranny fluid

Update from taking off the bottom plate from tranny. I didn't have a 24mm socket to remove the bottom drain plug so this is what it looks like.
https://cimg7.ibsrv.net/gimg/www.rx7...b8c93656fa.jpg


https://cimg8.ibsrv.net/gimg/www.rx7...68caee1a81.jpg


A lot more metal chunks.

https://cimg6.ibsrv.net/gimg/www.rx7...5c863b2a50.jpg


My inspection camera in the transmission fill hole. Notce gear with chips on each tooth.