transmission help needed

L

larry harding

Senior Member
hi guys i'm usually on the model a forum, but need a little help from this one.
i built a 50's style model a speedster with a lightened flywheel, 9" clutch and a 39 ******. i built the ****** using van pelts book and parts from scrounged doners. i need help with a couple of problems.
#1 the ****** shifts really good and makes driving a pleasure except for one thing. if i let off the throttle in second gear and deaccelerate it will come out of gear. what do i need to look for?
#2 i have a good thick disc in the clutch, but the fingers don't look right. is there some info on the net on adjusting the fingers. i know they need to be adjusted to match the thickness of the disc while on the flywheel.
 
it's a common problem in these cars and in manual transmission in general, the problem is often caused by worn parts, particular gears and synchronizers. back pressure on the transmission is the force that causes the problem. like when downshifting into 2nd or using it as a braking aid when descending a steep hill.

i can't help on the fingers problem.
 
You need a new thrust washer for your transmission.
I have had the same problem and with a NEW thrust washer installed, it stays in second gear.
Since you mentioned that you got parts from multiple trans, odds are that you installed a used thrust washer.
 
What part number is your syncro sleeve and hub? Could be the hub is not sliding over the 2nd gear teeth completely. you did check end play?
You have the adjustable screws on the pressure plate fingers, if so they can be adjusted to be even when the pp is not depressed allowing the throw out bearing to touch each finger at the same time. This is usually done by the Mfg.
 
yea.... a lot of used parts. i have the engine out now for other problems. i'll pull the ****** and check the thrust washer when i assembled the ****** it seemed to engage the gears good but i'll look again. i found a bit of advice on the finger adjustment on the internet, but looked at the face of the pressure plat i had used, it looked as someone had run a worn clutch to the point of the rivets on the disc eating up the face. kinda like brake shoes worn to the point of ruining the drums. got a new pressure plate on the way.
 
Here is a way to fix it without transmission disassembly noting that fixing worn out parts would be best but sounds like you've already done that.

587225
 
There is too much end play in the trans. causing it to pop out of 2nd.

Unfortunately, when rebuilding, you need to have the rear bearing retainer torqued up in order to test it properly. Which means taking it apart a few times if it's not within spec.

I'd try the tech article that Glen posted. Mac VP also sells a "helper" spring that you can insert into the detent spring to make it a bit stiffer as well.
 
Or, you can do what the old time stock car racers did : bolt a hook to the dashboard to keep it in second. I've seen more than one of those in actual use.
 
i was recently at a guys shop getting a shifter tower from him. there was a shift lever with a weird kink in the top end. he told me this was so the shifter could be hooked to the dash to keep it in 2nd gear. i suspect6ed this was or racing, but may have just been necessary for normal driving on a worn ******.
i built up two extra trannys for future reference and can swap out if i need to. the article about stiffer detent springs may be helpful.
.
 
As others have said, it is a result of worn parts - usually in multiple locations. Here are just some of the problems that can occur. The more of these issues you have, the more difficult it is to resolve them.

1) Excessive clearances/play between the snout of the main shaft and the front main drive gear. I would mic the snout of the main shaft to see if it is worn - if so, you'll need to locate a better one.

2) Worn caged needle bearings -- this is the one that goes on the end of the main shaft snout and runs inside the main input shaft. Beware - I have NOT seen a set of repop bearings that are worth a crap! Unless Mac VP says he found a supply, it is highly recommended that you reuse good originals or attempt to find NOS ones. The repop ones are usually not correctly hardened in the cage ends and they wear out in short order.

3) Worn 2nd gear bushing and too much slop/play on the fitment to the main shaft. The second gear needs a really precise fitment on the main shaft --> to the specific main shaft you're going to use. Frequently there is too much clearance, and this causes the second gear to "wobble" and this contributes to the problem. I have 'Charlie NY' re-bush my second gears to my main shafts - for just a slight drag between the two. This is one of the most important things you can do.

4) Cluster Gear Play -> too much front to rear play. This requires the fitment of the big thrust washers to setup the right play.

5) Synchro Hub Play and Second Gear End Play: There are thrust washers to setup the end-play between the synchro hub, second gear and the main shaft. Sometimes I have to use my surface grinder to accurately set the end-play. Sometimes I have to use a thicker washer and remove just a couple thousands from the back of second gear to set the end-play on the tighter side of the spec. I like to have about .002 to .003 of end play. It is difficult to "hold" the thrust washers in my surface grinder - which is why I sometimes have to massage the back-end of second gear

Okay - enough out of me . . .
 
tubman said:
Or, you can do what the old time stock car racers did : bolt a hook to the dashboard to keep it in second. I've seen more than one of those in actual use.
Click to expand...

so true!

there is a steep decent around where i live called Kirker Pass. the other day, while descending, i put it in second to avoid unnecessary stress on the brakes and had to hold on for dear life(!) to keep it there until i reached the bottom. ha

ordinarily i have little or no trouble with popping out of gear. so i'm thinking stress is a major factor. probably best not take the foot off the accelerator quickly while revs are high...in second, or third gear, for that matter. :)
 
Also, a lot of the modern ball bearings, the ones at front and rear of transmission, have thinner snap rings than original, l think around .006” thinner. So, unless you change them out to original dimensioned snap rings, straight away you’ve got .012” end play on your top shafts…
 
Brian said:
Also, a lot of the modern ball bearings, the ones at front and rear of transmission, have thinner snap rings than original, l think around .006” thinner. So, unless you change them out to original dimensioned snap rings, straight away you’ve got .012” end play on your top shafts…
Click to expand...

Good point, Brian. I always save those from old bearings
 
The factory snap rings for the two ball bearings were 0.075 to 0.077” thick. The snap rings that most mfrs place on today’s bearings are 0.064” thick. That’s 11 to 13 thousandth difference…..on each bearing location. This is a big deal and is the reason we started to have them made to the correct specifications years ago.

We save plenty of good used parts from core transmissions…..but never the snap rings. If you look at them closely, you’ll see a shiny wear pattern on the flat surface of the ring….where it fits into the groove of the ball bearing. This is wear. The flat surface outside of the bearing groove doesn’t really wear, but that’s not as significant for location of the bearing. All of the snap rings in the early Ford transmissions play a role in holding the end play. We’ve had all of these produced and all to the correct specifications. They’re made in the USA and aren’t expensive. Old used snap rings go right into the scrap barrel at our shop.
 
OK, I know this is not the PROPER way to solve this problem...
It's worked for me.
I put in a much stronger spring in the detent for 2nd-3rd gear.
Was careful to use a maximum length, without coil bind.
Can't tell the difference in the effort to shift gears.

Karl
 
Karl Wolf said:
OK, I know this is not the PROPER way to solve this problem...
It's worked for me.
I put in a much stronger spring in the detent for 2nd-3rd gear.
Was careful to use a maximum length, without coil bind.
Can't tell the difference in the effort to shift gears.

Karl
Click to expand...

good idea, hope it works forever! :)
 
Curiously, I have never heard of this problem in shoebox-era Fords. I believe the gearsets are essentially the same, at least through late 1951. I have had a few of them, some pretty worn out, but they all stayed in second gear whatever other problems they may have had. Was there a design change? Perhaps, substituting some later model small parts may eliminate this problem?
 
My experience has been as posted by B&S, and Glenn. I much prefer 'selected' used, original Ford parts, as opposed to many of the current new parts. Problem is, how to find the used parts. I've used up my old-time stash.
 
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