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1962 Coupe Deville - Won't downshift (SOLVED)

Started by JohnnyRockit, June 27, 2020, 04:45:42 PM

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JohnnyRockit

Well, I think I created an issue where one didn't previously exist.

I rebuilt the Carter AFB on my '62 CDV and was reading on the forum that I subsequently needed to readjust the rod for the throttle valve after rebuilding the carb. There were no problems with the way it shifted, but I thought I'd try to get the 2-3 shift a little smoother if possible.

I adjusted the rod per the Service Manual and it did seem to improve the 2-3 shift slightly, although I was almost out of adjustment threads that make the rod "shorter". I test drove it and decided to make it 1/2 turn "shorter" to see if it made any difference.

Well, it did. It felt like the throttle linkage was binding whenever I applied full throttle. After 2 or 3 full-throttle attempts, the binding went away, and so did any downshifting. What did I break?

All other areas of the transmission still seem fine, upshifts as well as always and downshifts correctly when coming to a stop...it just won't downshift to a lower gear at full throttle.

Any ideas where I should be looking?

Thank in advance!

Johnny
1962 Coupe Deville
2016 ELR

JohnnyRockit

And a quick followup...I just unhooked the throttle rod down at the transmission to check the movement of the lever going in to the side of the transmission.

It looks like the lever has about 1 to 2 inches of total movement back and forth, so at least it feels like it's still hooked up to the inner lever.
1962 Coupe Deville
2016 ELR

fishnjim

Any time you're out of adjustment thread, you either have the wrong part or somethings not right with the adjustment.   I think that rod adjusts on both ends.
Make sure you got it in the right hole on the carb linkage and going in the right direction.   Easy to misplace.   Some of these had different rods for different carbs, models.   eg; I had to get a different throttle rod, when I replaced the fast idle and pedal linkage and changed back to an original carb.   Had an after market on it when I obtained.   The rod on it would not even mate up.
No way I know to verify you got the right kick down rod.   They list but don't identify them per se in the parts list.

Omarine

Johnny that rod has a sweet spot where it will do all the shifting and it also needs to drop into 3rd when you give it lots of gas while in 4th.

Sounds like the rod is now slightly too long. One flat or two on the nut at a time will make a noticeable difference. Sounds like it needs to be shortened slightly to regain the 4-3 downshift.

Also be sure The throttle on the carb travels completely and doesn’t bind up like mine did with the return spring (previous owner had it that way).

Cheers
Oscar
1949 Harley Davidson FL
1952 Cadillac Coupe de Ville
1961 Chevy Impala 2 dr hardtop

JohnnyRockit

FishinJim, thanks for the reply but no parts such as rods, etc were changed and this thing worked fine for a couple of weeks after the carb rebuild. It was only after I did another adjustment that it got messed up. That when the binding feeling on the gas pedal started. And the rod only seems to have an adjustment on the carb end, no threads on the lower end.

Omarine, the trans currently shifts fine and I can do adjustments and change the shifts points...but no matter how much I adjust it one way or the other, there is no downshift. Are you suggesting I take a couple of 7/16" wrenches and just keep adjusting on "flat" at a time? Because I'll do it if that's what it takes.


Johnny
1962 Coupe Deville
2016 ELR

russ austin

Easy steps to adjust the TV rod.
1. Disconnect the throttle rod from the carb.
2. Loosen the nuts on the TV rod
3. Set the choke completely off and fast idle all the way off.
4. Slide the TV rod back to wards the transmission and hold there.
5. Adjust the front TV rod nut to touch the mount block. Now turn the nut 1 and 1/2 to tighten.
6. Adjust the back nut and tighten the nut.
7. Hook up the throttle rod correctly. Go from behind the throttle lever and towards you. You should be looking at the cut end of the rod, or the round end of the rod. The cotter key hole will be easily found, instead of reaching behind the throttle lever.  Installing the rod backwards will cause the bind you mentioned.
R.Austin

JohnnyRockit

Thanks for the suggestion Russ, but I did adjust the TV rod per the Service Manual, which follows the procedure you outlined with the exception to tighten the nut “3 full turns” vs your 1 1/2 turns. This morning, I backed it off using your spec and still no downshift. Also, the rod is installed correctly.

Here’s the thing. The rod adjustment is changing the shift points as intended. When I shorten the rod it shifts sooner and when lengthened it shifts later. Regardless of how it is adjusted, it would always downshift at full throttle. Now, there is no downshift no matter where it is adjusted.

Remember, everything was working correctly until I shortened the rod 1 turn and experienced the binding feel. I shouldn’t have kept applying the accelerator at that point, but I did a few more times. The binding went away and so did the ability to downshift. Now no downshift even after lengthening the rod and starting over on the adjustment.

Is it possible I damaged the downshift mechanism internally?
1962 Coupe Deville
2016 ELR

fishnjim

Anythings possible at any time with these old cars.   Part of the sting of ownership.   I don't like messing with these old trans.
Check the fluid, fresh and level, not brown or smelly, dirty.   Any crud in the shift control passages will mess it up.   Take somewhere and have them put on the trans cleaner that filters out the crud, if dirty.   One slug of crud and who knows what's clogged?
Disconnect the TV rod, stroke it backward, and run it a while like that, making sure trans shifts properly/right speeds, ie, the shift lever is properly adjusted, operating properly, and then put TV back on, adjust, and see if it'll downshift.  If shifting is not right, the down shift won't be.   These trans are temperamental and even after rebuild take some fettling especially, if any modifications/repairs.   I'm going thru some of that now.  I have no idea even if they rebuilt mine right either.  One step at a time.

savemy67

Hello Johnny,

On a '62 Hydra-Matic, throttle valve pressure and governor pressure are constantly struggling to provide the correct upshift and downshft points depending on engine load (throttle valve pressure) and road speed (governor pressure).  Under normal driving conditions, where mashing the accelerator pedal is not involved, an incorrect adjustment of the throttle valve rod will cause upshifts and downshifts to happen either sooner or later than is appropriate.

When the accelerator pedal is mashed to force a downshift, a small lever inside the transmission moves the throttle valve so as to provide enough pressure to overcome governor pressure (regardless of road speed), and a downshift occurs.  The binding you felt may have been the resistance of the lever and the throttle valve because your adjustment exceeded the travel of the valve and lever.

A screw holds the lever in place.  You would need to drop the pan of the transmission to see if the lever is broken, or if the screw became loose so as to allow the lever to rotate to a position the would preclude proper engagement of the throttle valve.  The attached photo is from the Master Parts List.

If normal upshifting and downshifting occur, this seems a likely candidate for your trouble, given what you described.

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

JohnnyRockit

Christopher,

That makes sense to me. I suspected that I'd need to drop the pan and possibly the valve body as well just to see what's going on since everything up top is adjusted correctly.

That'll be my project this week.


Johnny
1962 Coupe Deville
2016 ELR

Omarine

Johnny, i have had luck adjusting it one flat on the nut at a time. Seems tedious, but the book will only get you in the neighborhood, fine tuning follows. I usually take the 7/16 wrench with  me and go around the block until it’s right. I think mine is as good as it’s gonna get for now.

I wish you could check clutch plates for that 3 rd gear shift but not sure im willing to sign up for that right now...

Cheers
Oscar
1949 Harley Davidson FL
1952 Cadillac Coupe de Ville
1961 Chevy Impala 2 dr hardtop

JohnnyRockit

I ordered a filter and pan gasket which should be here by the end of the week.

I'm planning on dropping the pan in a day or so and will probably have to remove the valve body as well. I've never done transmission work besides changing fluid, filter, tailshaft seal and mount.

I will review the Service Manual for removing the valve body...anything "watch outs" I need to be aware of?

Thanks,

Johnny
1962 Coupe Deville
2016 ELR

cowboyman


JohnnyRockit

Well, this is the most embarrassing post I've written on this forum.

Before I put the car on stands and started working on the Hydramatic, I decided to go through all of your suggestions again to make sure I haven't skipped anything.

FishinJim, you suggested some basic stuff like checking fluid, etc. And I'm thinking that it wasn't so long ago that I did check the fluid and it was red, and the level was ok.

Well, today it was still red...but not until I added over 2 quarts to get it to show up on the dipstick! I mean, sure this Hydramatic has a few little leaks but I guess they add up over time.

I took it for a test drive and it shifts great, downshifts great...everything's great. I still have no clue where the binding sensation originated and I hope it doesn't come back.

So, thank you all for your help and suggestions!


Johnny
1962 Coupe Deville
2016 ELR

The Tassie Devil(le)

G'day John,

Congratulations on solving the problem before having to spend too much money.

And double congratulations for being human, and admitting it.   We have all made mistakes, but not all own up to it and tell the world.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe