lshlsh2 Hey Larry, I'm running 26" tires.

 

Qwik71442 So I used the calculator and I am really higher than what the chart says I should be at 60 mph. Since it could be the tach, after I make sure it's gong into all 3 gears (I'm 99.9% sure it does) I'll look at that first by hooking up a temporary tach to see what the reading is. Then it's just enjoy it until the new trans goes in. Thanks.

 

One more 200R4 tech tip: other than the governor, servo, and valve body, there is very little difference in the 200R4 in grandmas Cadillac, and what you will find in a grand national. The sun shell was heat treated differently starting around 1985, there were a couple other updates (the others slipped my mind at the moment) made around the same time but were done across the entire production line. I also recently learned the 86-91 turbo transmissions also got different carriers (the thrust washers in the carriers have different design) but otherwise interchange.

So, to sum this up: take the 200R4 from grandmas caddy, use a grand national servo or aftermarket equivalent, and some valve body/hydraulic upgrades, your good to go with a mild engine.

 

matt69olds That is what I've also learned. There's an '87 2004R about an hour from my house that I'm going to try to pick up, and Jimmy's Transmissions in WI (old timer) said he'll build me one. He's very popular on the Grand National Forums.

 

Ok, so here's an update. It most definitely shifts into 3rd. I got the oil changed today and on the way over to the mechanic I did both manual and auto shifts and I felt both the second and third gear shifts. While on the lift, we did the spin the wheel and count the driveshaft rotation thing and got 3.5 ish revolutions confirming the rear is in fact a 3.42. Until I do the trans sway, anyone have any other ideas why the rpms are at 3500 at 60mph?

 

You have a bad tach.

 

Joe P recently posted a BPO bell housing that is available for the 4L80 trans. Probably the best solution as the 2004r trans are wimpy in my opinion.

 

As said, pick up an aftermarket tach. The 2004R is fine with minor upgrades for mild Olds 350 an​​​​d a nearly direct swap. The 4L80E isn't easy or cheap for multiple reasons to install in these cars. I have done both these swaps. If he does have 3.42 gears, that is ideal for a 2004R.

 

Thanks everyone for all the help and suggestions. I'll definitely pick up a new tach to be put in when I do the trans swap.

 

If your car is running fine, why do a trans swap? Get a good tach and confirm the rpms are what you say they are and what all of us are saying they are not.

Horse, your water is a new tach. Drink.

 

I don't think you can make him do that ...

 

Koda because I plan on doing a lot of highway miles. Woodward Dream Cruise, Cruisin' the Coast, Rte 66 and more.

 

BangScreech4-4-2 You got that right, lol!

 

Bit of a joke there; I actually agree that you should confirm your numbers with a known accurate tach before making any decisions.

 

When a car with 26" tires is doing 60 mph in drive, with a 3.42 rear, it is doing 2650 rpm. This is geometry. If it isn't, either the rear isn't a 3.42, the tire isn't 26", you're not doing 60, or you're not in top gear. 3.42 rears don't require overdrive for highway speeds. If you absolutely want an overdrive transmission, that's fine; you do you. I am disappointed you see the need to talk back to people who have tried to help you despite your best efforts to stop them. Good luck.

 

Koda I'm not sure what you consider talking back. I think I've tried to answer everyone's posts politely and with as much information that I have. I'm very grateful for everyone's input even when they want to challenge the facts of what I'm observing, doing, etc. Perhaps a smiley emoji would help, but I did lol to BangScreech4-4-2 because I knew it was tongue in cheek. I'm also accurate in what I've been telling you and straightforward with why I'd like to put in an overdrive. I think maybe you just read something into my post that wasn't there or intended. Again, thank for the help and have a good one.

 

BangScreech4-4-2 Yeah, I know. That's why I did "lol". I know the car is going into all 3 gears by the feel of it shifting, BUT I didn't look at the tach to see if there was a drop from shift to shift and I'm just assuming it did. I know it's a 3.42 rear because I have the paperwork on it and by spinning the wheel and counting the rotations of the driveshaft with a mechanic that roughly 3.5 turns was counted. Since I want to get an overdrive regardless of what's going on, I'm not going to worry about it too much, but I do like the suggestion of getting another tach or temporary tach to see if that's the problem. Thanks and have a good one.

 

olds 307 and 403 It looks like that is what I'm going to have to do. Either way, I'm getting the 2004R, but I'd like to know what's up with the rpms before I do that. Thanks.

 

You can get a new tach or you can calibrate the one you have. Either way, you need to get your hands on a different tach. I think someone on here posted the complete Delco manual on here, and I thought I downloaded it. BUT, I can't find it now.

 

OLDSter Ralph Thanks, I'll look into recalibrating as well.

 

As I recall from memory.........This was for 1967 and previous years. I am ASSUMING they are pretty much similar later tachs. There is some silver tape on the back of the tach that covers an adjustment slotted screw head. Turning one way raises the tach reading, the other way lowers it. AND the screw is very sensitive.......a little tweak makes a large difference, so be patient.

 

OLDSter Ralph Thank you! I'll still need another tach though, right? I mean, I still need to verify it's the tach that's off and determin the true rpm's. Then I can adjust the screw on the original tach until it matches the temporary one, right?

 

Correct. You could borrow one ? Do you own a dwell tach ?

 

OLDSter Ralph I don't own one, but I have a neighbor who is a retire mechanic. He used to work on my 71 Cutlass and 78 Vette and own around 8 classic/muscle cars himself. He still has his shop, just doesn't work anymore. I'll ask him. Thanks again.

 

Im late to the party but just in case.............

https://purperformance.com/p-29669-rpm-calculator.html

 

Nice calculator, like the recently defunct Olds Gmail calculator, the rpm is accurate with the torque converter locked up. Add 200 to 300 rpm for a non lock up converter.

 

So just giving an update... I had my mechanic confirm that it is in fact a 3.42 rear, th350 trans, 27.5" tires, and he said my tach has to be bad. No other explanation. Using all the calculators that are out there, the tach is off 600-700 rpm's. I'm getting new mufflers put on and the rear glass reset (maybe a little body work with that too), replacing the radiator and water pump myself, then I'm going to search for a 2004R core. Hopefully everything will be done by the middle of June.
Thanks again for all your opinions and assistance! Have a great weekend.

 

Nice !

Finally absolutes to work with. Is she stock and how is the pickup ? Depending on rim tire combo you may be +20 lbs each on back. (15 x 8 Cragar and 275 60 15 T/As combo weigh 63 lbs per wheel).


As far as rpms go.

60 mph, G78-14, and, 3.42 = 2700 rpm with TH350
______27.5 inch tall , 3.42 = 2600 rpm with TH350
_________________, 3.42 = 1800 rpm with TH200-4R
(rpms are rounded to nearest 100)

 

69CSHC yeah the tires really fill out the wheel wells. They're staggered 15" Cragars. She's stock with a strong engine and quick off the iine. Also a great kick-down when passing. 2.5" dual exhaust and right now, a little loud when I get on it. Super clean car too. New frame, coil overs, solid panels, newer tires, brakes, and a new interior. Just needs the 2004R to be 99% complete. Next year will be Vintage Air and it will be done! Have a great weekend.

 

“next year will be vintage air and it will be done!”

HA! Who in readerland believes that?! Project cars are NEVER done. There is always something to try, or improve.

 

That is the whole reason to have a project car. Each year I do something that improves the drive or the car. This year I went with a new steering wheel and a Tick shifter ($$$$). Last year it was a HUD. The year before that was a cam. You get the picture.

 

👍

My apologies I don't know why but I thought you had a 71.

F78-14s are for 71, G78 -14s are for 70. G78s are much larger, I will revise my previous post.

 

Last update... Flowmaster super 40's is what it had. Today I had Flowmaster FlowFX mufflers put on, and that "screaming" the car had at 60mph is gone. Yeah, you can tell it's still wanting another gear, but what a difference the sound makes. I'm still going to get the 2004R and I'm still going to fix/replace the tach, but the urgency of doing those things has dissipated.
Thanks again to everyone for your input.

 

Glad it worked out somewhat.

Sorry it took so long, 4 months and 70+ posts but you never complained about exhaust noise. What was bothering you is Flowmaster 40s notorious droning at speed. It's almost as famous as their signature sound. And it happens at the speed you were concerned with. But the speeds real RPM not the incorrect tachometer reading. It happens around 2500 rpm. The faulty tach readings made it seem like it was high revving because of the drone happening at the same time.

 

Yeah, I went from one blown, one Ok, Aero Chamber muffler, terrible drone. I went to Dynomax Superturbo's, too quiet. The Flowmaster FX being straight through, no doubt flow better than the restrictive Super 40's but are quite quiet till you floor the gas. I am cruising 2000 rpm at 60 mph. If I could actually get the lock up converter to lock, 1700 rpm. It is a $50 Amazon controller for the 4L80E, real controllers are $$$ and my Holley Terminator X Max is toast. Just make sure to get a few upgrades when the 2004R is built. I have killed probably 5 with my weak junk. Everything else I own is overdrive, a person gets used to 1500 rpm to 2000 rpm going down the highway, it's great.

 

Overdrive transmissions are an idea that, once it gets into someone's head, it never leaves. They're simply not necessary for most rear ends and encourage driving faster at cruise than the rest of the car was designed. Most people don't upgrade suspension, steering, brakes, seatbelts, but have no issue with doing 85 in overdrive at cruise with very little ability to slow or steer at that speed. Good luck.

 

Those darned kids going fast! I can tell you when I was a young lad I cared not if my brakes worked properly or if I could go around a curve. So, great points here. First car a 69 Chevelle w/ a small block, powerglide, and a 3.08 open rear diff. It was perfect for a hooligan. Not very fast but w/ a decent cam it sounded like you were.

Nowadays, I had a CTS-V that ran bottom 11s. That's too fast for a kid but they all have them including the Hellcats.

 

I do not understand why people crusade so hard against an upgrade that has zero downsides, beyond the initial cost. Better fuel economy, better acceleration, less wear and tear on everything associated with the engine (bearings, valvetrain, accessories, cooling system, etc), less noise, less vibration, and, in the case of a 200-4R, it bolts in with almost no modification. Hell, the character of the car even stays the same. You get a car with the standard 3.08s AND the optional 3.90's, all in one!

Not all of us are stock purists. Some of us have no problem upgrading our suspension, steering, and brakes to match our overdrive transmissions. As for seatbelts, these things are deathtraps at 30 mph. Hell, they're deathtraps sitting at a stop light if you get rear-ended by someone doing 30 mph. And if we're really concerned about safety, maintaining the speed limit of 80 mph in some areas of the country is far safer than puttering around at 20-25 mph below the speed limit. Been there, done that in Utah and I'll never do it again.

If you like pure stock cars, have at it. But don't expect me to buy, build, and keep it for your pleasure.

 

As said the 2004R has no downside besides cost. It will basically make his 3.42 act like 2.56 on the highway. Actually more horsepower that what I have in my 70S is something I have decided against. The brakes and the handling are barely enough with what I have. Actually having traction with this posi makes it very squirrely, it grips too well.

 

Why would I care about what you do with your car?

This thread has been about the OP having to have ten guys tell him his tach is off and he doesn't need an OD trans to not blow up his engine. We finally got him to figure out what his engine is doing, and he still thinks he needs one. He doesn't. He may want one, he may like how it drives with one, but, does he need it? No.