In trying to help a fellow Stovebolt member, I've come up against some problems and need help. I apologize for the long post.
Background: 1954 Chevrolet 3100 with Hydramatic that was in the family and it is his first set of wheels. He's trying to bring it back to life but has limited finances. The transmission has been rebuilt and converted to open drive using parts from a 1956 Chevrolet Hydramatic. The owner does not know if the "old guy" that has experience with this transmission is still living. To complicate matters the rear axle was changed to a 3.38 ratio. After fighting the battle to make his Rochester BC work properly, he gave up and installed a rebuilt Carter YF 2101S. This has worked well and he is now on the road "having the time of my life". He still has other bugs to work out. As far as the transmission, upshift works. It does not downshift going uphill and there is no passing gear.
I happened to find information that the 1954 Cadillac and 1954 Chevrolet Truck 3100 has the same transmission gear ratio. Also one of the option rear axles for the Cadillac is a 3.36 ratio which is close enough to a 3.38. The Cadillac manual lists the MPH shift points (range). Copy of pages attached.
Documentation we currently access for reference: 7 part Servicing Chevrolet Truck Hydramatic 1954 Chevrolet shop manual Paul Marsh Hydramatic Transmission Service Manual 1946-1955 Hydramatic "on the car" Adjustment Service Manual
The owner has none of the special Hydramatic tools.
I think the first thing to do is set the throttle properly (get us in the ballpark) using gauges J-2545-C and J-5609. As I said the owner doesn't have them. Can a person make their own gauges? Does anyone have dimensions? The J-2545-C is a thick bent metal and/or welded L shaped bracket. One end is held against the transmission rear and the other end has a notch for "Chev". I think gauge J-5609 only holds the bell cam in a maximum fixed position? I was thinking maybe wire it into position?
Last edited by buoymaker; 07/29/20224:47 AM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
That transmission is VERY sensitive to throttle pressure adjustments. If you disconnect the TV linkage at the side of the transmission, you should be able to move the lever through its range of motion. You'll feel a spring loaded detent near the full travel position that's the forced kickdown (passing gear) that causes the 4-3 downshift as the throttle reaches full open. The geometry of the throttle linkage also has a pronounced effect on part throttle downshifts. The 1-2 shift happens very quickly, at probably less than 5 MPH, and even when the TV pressure is right, there will be a somewhat rough 2-3 shift. In the late 1950's the Hydra-Matic got the nickname "Jerk-O-Matic" because of that rough 2-3 shift. Contact FATSCO transmission parts in New Jersey to see if they know who might have the adjustment fixtures for sale or rent. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
This guy (can't remember his name) supplies HM parts and his web site says he rents out the adjustment tools. Scroll most of the way towards the bottom of THIS PAGE.
That 2-3 upshift can be wicked because it requires a band-to-clutch change in one planetary set and a clutch-to-band change in the other at the same time. Improper adjustments lead to 2-4-3 shifts when the front set shifts faster than the rear set and 2-1-3 shifts when the rear set shifts faster than the front set.
I think the best book for us amateurs to use while tweaking adjustments on HM transmissions is THIS ONE
From experience (daily drove a '57 GMC with Hydra-Matic for 21 years) I think doing the band adjustments using the internal tools (requires dropping the pan) gives much better results than using the external tools.
Last edited by Bill Hanlon; 07/29/20224:07 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
You say he has no downshift going uphill. Will the car downshift if he manually shifts from D1 to D2 (not Lo)?
'56 Cad. P-N-D-D2-Lo-R I assume his Chevy is the same? Maybe without P.
I also notice that the transmission is a hybrid of 1954 and 1956 Hydramatics. Depending on the '56 parts used, that might be the source of his trouble. The '54 and '56 Hydramatics are not interchangeable even if some parts look identical.
My '56 Cadillac transmission had a Pontiac valve body and was never able to be dialed in properly by the book. Obtaining the correct '56 parts for the '56 transmission solved all my issues.
Last edited by Otto Skorzeny; 07/29/20226:56 PM.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
The Dual Range Hydramatic does not have a Park position. Putting the shift lever into the R position with the engine stopped locks the driveshaft. If it's got Park, it's a "Controlled Coupling" transmiission, one that's radically different than a Dual Range, and much less rugged. It does shift smoother, however.
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
At first I was worried that a 3.38 versus 3.90 rear axle would mean the transmission would shift at wrong speeds and the results would be poor. Not so. Cadillac has the same transmission gear ratio as the truck and there is a 3.36 rear axle ratio example, so the combination is good. That's the only reason for mentioning Cadillac.
The transmission does not downshift at all. So that's why I'm thinking the throttle linkage setting is way off. Not even close to approaching the detent. The owner has other issues to deal with so communication with him is sporadic.
Last edited by buoymaker; 07/30/202212:53 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
Somewhere I have a table that shows the measurements of various cars and trucks of the era that is sort of a poor man's Throttle Lever Checking Gauge. I'm not sure if it cover's '56 Chevy trucks (would also need to know 6 or V8 - they are different on GMCs - I don't know about Chevys), but I can look for it later this afternoon. It would at least get you in the ballpark.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Bouymaker, I also think the throttle linkage is way off.
It is extremely sensitive to slight movements forward and backward of the adjusting nut. Literally a single thread can make the difference between a smooth shift, harsh shift, or no shift.
Last edited by Otto Skorzeny; 07/30/20223:41 PM.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
A half turn can make the difference between shifting all 4 gears inside 50 feet and not downshifting for a turn. That being said, I have seen the throttle pressure arm break loose from the shaft internally. I think the 7 booklets describes adjusting pressure with an actual pressure gauge. That may tell you if it is or is not working.
Set my computer to search for h*.jpg and h*.pdf, took a nap and when I woke up it had found this. Don't know if it'll do any good. The listings are all for GMC trucks and trannys. Finding a throttle gauge is likely a better answer.
Last edited by Bill Hanlon; 07/30/202210:42 PM.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Chevrolet Trucks, Lever, Throttle Control Outer, 8618043 1954-55 1/2, 3/4 & 1 Ton (6 cyl.) 1956-62 All I6 and V8 uses the same throttle lever but unfortunately it is not listed on the cheat sheet in the above link.
I've been studying the 1955-59 GMC manual and came across this page. http://chevy.oldcarmanualproject.com/gmc/5559mm/5559mm632.html 4-23/32 or 4.7187 from the rear to the center of the trunnion hole on the throttle lever. The dimension may not be correct for Chevrolet Truck and 1954 GMC.
Throttle Lever Gauge: 1954-55 Chevrolet truck J-2545-C 1954 GMC J-2545 B and C 1955-59 J-6188 (series 100, 150, 250....PM250) Looks like the GMC throttle lever changed in 1955.
Last edited by buoymaker; 07/30/202210:42 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
The AACA post you linked to is using the external adjustment tools to set the bands. Has nothing to do with throttle linkage.
The tranny in question being from a '54 Chevy truck (there is a label either on the passenger's side of the main case or on the lip just above the rear of the pan and to the left of center that will ID the model of the transmission) and I assume that the linkage is also from the same '54 Chevy truck, so I'd make the adjustments using measurements for a '54 Chevy truck.
As others have noted above, getting the throttle adjustment right at the tranny is very important with Hydra-Matics. And one turn on the trunnion can make a huge difference. GMC documentation specifies +- 1/32" and that is just to get you close enough to start adjusting.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Even the bad scan that I have of book 2 is too large to post here but here is an ebay link that includes book 2 which covers adjustment with special tools. https://www.ebay.com/itm/314044077772?hash=item491e7c56cc:g:jFMAAOSwWCRisdG9
Yes and no. It does start out by talking about band adjustment.
Scroll down. Quote: "Your throttle valve linkage in the early model Hydramatics is a very important setting for proper operation. There were many different linkages used throughout the years. There should be a code stamped on the linkage so you can adjust it. Each style is adjusted slightly differently. The measurements are taken with the throttle rod removed and the lever held against the rear stop. You adjust it to the proper dimensions by bending the rod."
My words here: The throttle lever is against the internal "stop" and the dimensions (A, B, C, D and E) are then measured. Bend the arm to meet the dimensions.
Chevrolet truck manual. Quote: Under the truck, disconnect the control rod from the transmission throttle valve lever. Hold the lever against the rear stop and check the distance from hole in the lever to rear of transmission case, using gauge J-2545-C. If necessary, bend the transmission throttle valve lever.....and so on.
The owner doesn't have the gauge and I was hoping to find something, make a tool or measure distance, to get the initial throttle lever check. Lord help us if the lever needs bending. Fingers crossed.
Last edited by buoymaker; 07/31/202212:31 AM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
There you go. That was the link I was looking for. I had the original scans but they were too large to post here. Thanks!
The adjustment tools are pretty straightforward. The one tool has you disconnect the throttle linkage from going up to the carb and locks it in a reference point to a hole in the pan rail of the block. Then as mentioned, it has a groove that lines up with the hole in the lever. There were multiple slots for different applications. The Snap-On Tool version is "full of holes"
