Did GM originally use the color coded gears in the 700r4s? When I go to pick a part, I want to know if I can just go by the colors of the gears.

 

Yes, original GM gears are colored.

 

SWEET, now all I gotta do is find

40 tooth driven
and

15 tooth drive.

Thanks!

 

15-tooth drive gear part #8642620
40-tooth driven gear part #25513047

Any parts store should be able to cross-reference them. But they might be hard to come by and you might need to talk to the dealer.

Hope this helps.
Lou

 

im getiing 3.42 gears and i have right now 2.73,wat gear drive do i need to have to get an accurate speed reading?

 

Hold on, you have 2.73's with an auto?

Anyway, for an auto tranny and 3.42's, a good combination would be:
15-tooth grey drive gear (#8642620)
41-tooth yellow driven gear (#25513048)

But what tires do you have? Assuming your RS has stock tires (215/65R15), the combination is different:
- 17-tooth red drive gear (#8640517)
- 45-tooth light blue driven gear (#25513052)

So what size tires are you using?

Lou

 

No. They can vary. There are some that stay consistently correct, but then you'll see another one that's wrong.

 

Uh, why dont you just go to the dealer. For both gears, they are under $10 list. They can look them up by rear end ratio and tire size. Beats playing around at a junkyard, with the possibility of not findind what you need.

 

well i do have at the moment the stock 15' wheels but i will be getting 17' zo6 wheels later on

 

i dont mean to hijack the thread but with all you guys that know what your talkin about i wont start another one . I have a 700r4 and i have 4.10 gears and stock size tires , what gears do i need and part numbers and colors do i have to get to get it close .

 

But when you switch to the new wheels, you might need to change the gears again to compensate for the change in overall tire diameter.

Lou

 

Well, with 4.10 gears on an auto, you're pretty much SOL.
There is no precise gearing for the speedometer but you can install the highest gears possible (15:45) and you would be off by 6% (showing 53 mph at 50 mph).

Increasing the tire size (by 6%) would solve your problem.

Hope this helps.
Lou

In Edit: Forgot to mention the part #'s.
- 15-tooth grey drive gear (#8642620)
- 45-tooth lt blue driven gear (#25513052)

 

heres a tough one for you guys. even the GM techs here cant find me a combo for speedo gears. 1988 2.77 rear end , 1986 NWC T-5 and a 350 TPI he says that the T-5 never came 2.77 rear end but the original 700-r4 did. so he said the are no such speedo gears is this true any help will be helpful

 

1988? Camaros still had the cable driven speedometer at that time, right? I don't have part numbers for that, only for the electronic VSS gears. Sorry.

 

yeah its all mechanical unfortunatly. af anyone can figure this one out i comend you! thanks for the help

 

big baby lou you rule ,i got he gears , the were like 12 bucks for the both of them , i ordered them in the afternoon and they were there the next day at lunch so i was happy about that . Now , how do i change the gears , i think one of them is easy right , and then the tailshaft has to come off to do the other . What kind of job is it to take the tailshaft off , and do i have to drain the fluid or will just jacking the rear of the car up suffice.

 

You're right, the driven gear is easy. But the drive gear is in the tailhousing. And I have never taken one off so I won't be much help to you, sorry. Do a search and you should find a lot of info.

I would drain the fluid, jacking up the rear won't be enough, the tailhousing is much lower than the fill plug and you'll get fluid all over you.

 

o crap , i just found out i think from reading old posts that you gave me the wrong part number , this lt blue/green gear is for an electril speedo , i have a mechanical one , so i need one with a shaft attached to the gear?I still need a 45 tooth one , so does anyone have the part number for that .

 

Dangit, I am sorry man. Why did I think you had '89 Trans Am? Those had the electric VSS pickup.
If you fill out your bio (shows up to the left of your post), this kind of mistake will not be repeated. I'm sorry once again.
Hopefully you can take the gears back and they'll return your money, these are not special order items, there should be no problem.

Unfortunatelly, I don't know much about the mechanical speedo gears but I'm searching, hoping to learn and then answer your questions.

Lou

 

Ok, finally found something. The info is not exactly plentiful on the web, I'm surprised.

The part number for the 45-tooth (lt blue) driven gear for a mechanical speedometer is 25522497.

Hope this helps.
Lou

 

hey thanks man , i didnt realize i wasnt specific on what i asked. I have the gear i dont think i can return it but its only 6 bucks so i dont even care, no biggie, i just hope i dont need a different sleve . o well ill find out . thanks again.

 

To answer the question from your PM, I found the mechanical speedo gear part #'s at http://www.442.com/oldsfaq/oftrn.htm but there might be more out there.

As for the 45-tooth VSS gear, I am sure someone will need one soon. I know a lot of people put 4.10's in their cars (why? I have 4.10's in my truck for towing and I'm rowing gears like crazy, with top speed about 70mph). So if I see someone ask about a speedo grear for 4.10's, I'll let them know you have one available!

 

ok thanks, it only cost liek 5 .83 so it wont be much for the gear .

 

Hello there,

I'm wondering if you can help me... (I need lots some would say)
I have a 1989 Camaro 2.8 stick with 3.42 gears. I have installed a 1990 350 and tossed a 84 tranny behind it with a limited slip rear end with the same ratio as my 89. I'm wondering if you'll know the GM number for the gear for the speed sensor (electrical). I see that in 1990 and later, G92 Camaros had a stick tranny and 3.42 gears.......
Thanks for your help,
Charles Kent

 

Sure, bud! That's what we're here for!

BTW, that's an easy one.
VSS with 3.42's with a manual requires the 7:19 combo. I.e.:
- 7-tooth purple drive gear (#14071731)
- 19-tooth white driven gear (#14090592)

Provided that you have one of these stock tire sizes:
215/65R15
245//50R16
235/55R16

If not, we'd have to recalculate to compensate for different tire.

Also, make sure you have the 7-tooth PURPLE gear in the tailhousing. Becaue they also put a 9-tooth RED gear in there. The best method is to mark one tooth, rotate the tailshaft and count the teeth.

Hope this helps.
Lou

 

hey lou , i iwsh you were right about the speedo gear, i went and ordered the right one for the cable driven speedo , and the gear , just the stupid gear is 40 bucks , i guess their discontinued but a place in michigan has 290 of them . but what a rip its basically the same thing with a pecker that sticks out and has a hole in it for the cable . 40 bucks , what a rip .

 

Yeah, been there, my friend. Had to order the gears for a MANUAL tranny VSS and guess what, they cost me $40+, AFTER an employee discount. Heck. And the T-5 VSS itself cost of course twice as much as the stupid auto VSS. Exactly same thing, smaller size, more bucks.

I was told that the pricing is based on availability and that if they discontinued the item and have only a few left, they'll jack up the price. There's always a duma** that will pay that much because he can't drive without the part. Duh!

They're milking us!

You know what? If you haven't ordered yet, try looking at this page. Or give 'em a call, they'll talk you through the gear selection. They are reasonably priced and might have what ya need.

http://www.transmissioncenter.net/sp...n_______va.htm

Hope this helps.
Lou

 

hey guys, i just pulled the speedo gear the driven one and it was broken , the piece sticking out snapped , since it was plastic, well it had a purple drive and yellow driven

so it wasa 10/41 , what would those gears be correct for , and what will happen if i put a 45 in there now , so id have a 10/45. I have the driven gear and drive gears in hand im just wondering if i should take the tailsahft off .

 

Hey Lou - I need some help in this area as well. I'm temporarily using a WC T-5 that came with a mechanical speedo hook-up. My 91, which has 3.42 gears, used the VSS so I bolted it up to the temp replacement tranny (mine is getting "upgraded"). Anyway, what do I need to do to get the right VSS signal using a WC T-5 with 3.42 gears? I've played with the VSS value in the prom and got the ECM showing the correct speed and it looks like the tranny was used on a 2.7x geared car. Does the internal gear have to be changed, or is this a VSS swap to get the speedo corrected?

Also - to make matters worse/harder, I'm supposed to be installing a Ford 9" on Wednesday. It will either have a 4.11 or a 3.70 geared rear, depending on which one we put in it at the time....

I'm still running the '91 factory sized 245x55R16 sized tires.

Sure hope this is a simple VSS swap.....

 

Ive got a 89 camaro that had stock 2.73 gears in the 700r4 i upgraded the rear to a 9bolt 3.27. to my understanding they changed from mechanical to electric midway through the year. how can i tell if i have a mechanical or electric? it looks like i got the connector for an electric thats hanging by where the gears meaning this is mechanical? or is that just some kind of diagnostic wire?

 

Some good info in this thread. Hope it makes it to a sticky or at least something off it.

 

Ok, I'm back.

Sorry for the delay, I've been out.
Another strange thing is that I got about 15-20 email notifications of a new response in this thread last week. But there was no response. And I finally received a notification today when there already are three here. The system has oficially gone haywire.

I'll reply to all your questions, one by one.
Lou

 

You say 10 teeth on the drive gear? That is unknown to me. And you say it's purple. I know only of two drive gears that are close to 10 teeth and they have 7 or 9 teeth and are meant for a T-5 tranny. I can't find a 10-tooth drive gear in any sheets.

I demand a recount! Ok, ok, this one is getting old. Can you please try to count the teeth again carefully, maybe it's not 10. It wouldn't really make sense, especially in an automatic transmission (the gears have 15, 17 or 19 teeth).

Lemme know how the recount goes.
Lou

 

What you need for your current 3.42's is the 7/19 combination:
- 7-tooth purple drive gear (#14071731)
- 19-tooth white driven gear (#14090592)

If you put in a 4.11 Ford rear end, that won't be a problem because this is close to GM's 4.10 rear that uses the 7:22 gear combo:
- 7-tooth purple drive gear (#14071731)
- 22-tooth grey driven gear (#14090595)

With the 3.7x gears, it'll be a little harder but hopefully you'll be able to obtain a 20-tooth blue driven gear (not so common). Part # 14090593.

Hope this helps.
Lou

 

How can you tell you have a mechanical or electric speedo? Hmm. I'd look under the car and see what's coming out of the tailshaft. If it's a thick cable, it's mechanical. If it's two wires, it's electrical.

Hope this helps.
Lou

 

Lou - that's the info for the electrical VSS set up on a manula tranny? Just verifying......

 

can i have a recount , ahahaa, what are you florida. well i got two pics for you , I was correct a 41 and a 10 , thats what he had in there , and i remember it was slow for the 410 gears , well now i have a 15 and a 45 and when im doing 30 it says 35 and then im doing 55 it says 62 on the speedo .

Also when installing the drive gear, get water and put it in the microwave for 40 sec and then put the gear in there and it expands it and makes it really easy to get the gear on since the fit is so tight . So there a good tip we learned when doing this .

 

also when i ordered the 45 tooth driven gear and it was 40 bucks i thought it was high but it also came with the sleeve .So that was good.

 

You said you had VSS so I looked up the values for the VSS gears.
Lou

 

Ok, you were right, that's what I was afraid of. But I found an explanation. You had one of the mechanical speedometer drive gears in there. It's a purple 10-tooth gear (#8628838). I forgot about the mechanical gears completely.

As for the speedometer deviation, I am surprised. The formulas specifically indicated the 15:45 gears as the best possible combination. I'm stumped.

I'll research a bit more but meanwhile, I can say that if you want it to show 55 at 55, you might need the white 13-tooth drive gear (#8634934). Why this does not correspond to the gear calculation formulas, I don't know. But I'll find out! Gimme a minute.

 

Can you indicate your exact tire size here? Maybe that's another factor influencing the outcome of the formula.

Thx
Lou

 

well i hope your wrong about the 13, im not changing the damn drive gear again , that was a pita, and i dont wanna do it again , but my tire sizes are 275/35-18 in the rear and the specs say that they are 25.6 inches tall.

 

Ok, that's one place I was off. I used your stock tire size to calculate the gears. And 255/55-R15 is a 26" tire, not 25.5". So there's a half inch difference. But that still does not explain why your speedometer is off so much.

If you look at the following formula:


and punch in numbers for your car, you will get this dependency:
# DRIVEN TEETH = 3.11 * # DRIVE TEETH

If you have a 15-tooth drive gear, that tells you you need 46.7 driven teeth. But the highest gear is 45. That's why I recommended it.

With this little deviation, your speedometer should be showing 57 at 55 mph, not a very big difference. I said before that it would not be precise but the actual result now is way off.

Stupid question (don't hate me for it, please ) but is your speedo accurate or could it be off?

In your situation, dropping the drive gear from 15 teeth to 13 teeth would give you a -13% change, which is exactly what you want your speedo correction to be (-12.7%). My suggested gear combo should have been 2% off. Why it's actually 12%, I have no clue. It's a mystery (for now).

 

well theirs now way to know if the speedo is correct or not , since its not correct , the only way to know is if someone else had 4.10s and stock size tires and the same setup then we could compare the speedos, but i used a gps on the car i know its correct , and to bakc up the gps , our avalanche was dead on and so was my grandfathers saturn so im pretty sure gps is correct , but its better than nothing , but the whole reason i did this is because i was told that i would have drivability issues and that the tcc might not lock up , well it drives the same and i cant tell if the tc is locking up . But at least i have a speedo , too bad it cranks up the miles too much . But o well, thanks for all the help with the speedo .

btw , what would the speedo be if i got a 10/41 again , my gradfather seemed to think that would have been slow , but i dont remember since it was last year i drove it when it worked.

 

i just the calculations and with my tire size i would need a 48.4 tooth gear , so a 48 or 49 .

 

How was the speedometer before the rear end swap? Did it read reasonably? Mechanical speedometers are prone to failures with age so I wouldn't be surprised if it was off a bit.


That would make the speedo way to slow, precisely 28% slower! Meaning, it would show 43 at 60mph. A "bit" off, eh?

As I recommended before, if the speedometer is 13% faster right now, you can drop the gearing 13% by swapping in a 13-tooth drive gear instead of the 15-tooth. I'll buy your 15-tooth gear.

Lou

 

Yeah but the highest they make is 45 (no 48 or 49). That's why I recommended it. It would have been off only 2%.

 

Can anyone tell me what gears are nedded for my stock 89 formula TBI. I'm running 245 50 r16's. The speedometer is icncremently off , not in my favor. My speedo reads 38 when I'm actually goin 30mph. It reads 70 at 55mph. If there is a remedy using a different gear , can someone help me. If it sounds like something else either.

 

Not enough info to help you.
What's your rear gear ratio? (RPO codes will tell you if you don't know)
I take it you still have the auto (from your member info).

 

Here's are some awesome calculators on TCIs page.

Automatics of course.

http://www.tciauto.com/tech_info/speedo_gears.htm