VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 Knee Action Suspension

Can anyone tell me the years specifically that the knee action, Dubonet front suspension was offered on Chevies? I think it was 34 - 38, but I would also like to know if the basic suspension is identical between years (other than frame width). Are the large spring "holders" (large cast metal pockets for the springs / built in shocks) at least the same? Were there other GM makes that used the same identical set-up? Thanks!

The knee-action units were used by Chevrolet from 1934-38 and Pontiac from 1934-36.Was also used on Opels in Germany.
There were several changes made each year from 1934-37.The 1937-38 is the same and had all the latest improvements.A 1938 can be used on a 1934.A 1934 can not be used on any other year due to the fact that the spindles stuck out farther.Would fit but hub caps can not be installed.The 1934-35 had the spindle flange riveted to the big arm.1936 and up spindle was swedged into the arm.The shock absorber valving was changed over the years to make them more firm.People complained that the earlie models bounced too much.Were accustomed to the rigid, hard riding, leaf springs.The inner coil springs were the same from 1934-38 except the 1934 with side mounts used a heaiver spring.The front riding heigth is adjustable.The 1937-38 units are mosr desireable.1936 OK....but all are usually worn out from being run low or with out oil.When they are in good condition and the steering is "tight" they are a wondeful driving suspension.
The Pontiac units are slightly different due to the different brakes Pontiac used,etc.Main parts are the same.

Thanks Gene, wow, I am going to start calling you "411"!! :) What are the spring "cases" called by the way? (those big, HEAVY cast pieces that the springs go inside of) If I am hearing you correctly, these "spring cases" are the same on 34 - 38 Chevies and 34 - 38 Pontiacs, and the outlying parts will differ? Can you tell me how the ride height is adjustable by chance? Finally, I don't think there is any camber adjustment with this system, simply caster by adjusting the tie rod ends, but do you know about alignment issues? It's a shame so many Chevies of this era are cut up for a Mustang II front end to get rid of it, when I think this is a workable system that could even be improved/modified without changing the originality of the car - it's essentially a 4 link front suspension with built in shocks. Is there a good source for repair/parts on these unique front suspensions? Thanks again Gene!

Richard:
The knee-actions sure make for a nice ride but they can be difficult to maintain. The original needle bearings will fail quickly if the units are run without lubricant. There are several places that advertise in G&D and Hemmings that can repair these. I had mine done years ago with new roller bearings and seals and they've been trouble free.
Ride height is adjusted by turning the threaded "plug" at the top of the unit. Take the locking plate off and juice it up with penetrating oil. As I recall, the manual says not to screw the top in so it is more than 1/8" below the top of the female threads. Tightening the spring essentially compresses the spring and that increases ride height. If the springs are too tired, replacement springs may be needed. There is a specified height adjustment in the manual...I recall it's something like 5 3/8" inches from the hub to the bottom of the backing plate. I'm doing this from memory as I'm not home at the moment.
Two last items...some use hydraulic jack oil and others use ATF to top off the lube level. From time to time I've seen reseal kits on Ebay.
Good luck!
Coach

The "spring cases" are the housings.They are not cast but stamped.The Pontiac "out lying parts" are different.The ride heighth is adjusted by loosening the bolt, top center, and turning the bar either direstion.Its explained in the shop manual along with the alignment proceedures.Also the 1937-38 Dealer News has more info...they are available in reprint from the Filling Station.The caster and camber would be adjusted by bending the cross member....the toe-in is adjusted by the tie rods.
The suspension did have some short commings as did all styles back then.The disadvantage is the wheels leaned with the car rather that opposite the car in corners, as the short arm - long arm does.There will be more info in the material that I am sending you.If worn out its best to have professionally rebuilt at about $400.00 each.This does not include the lower, small radius arms which are easy to replace.Hard parts are not easily available.
Back in their day the dealer did not even fool with them.They just exchanged them with rebuilts that were available from Chevrolet and others.The ones from others were not always "good".
I recieved your letter and am working on the project...its taking a little longer than I anticipated.You will be pleased with the results.

I've owned my 34 Master for over 30 years and when I first bought the car, I pulled the knees down and replaced all the seals, this gave me about 35,000 miles of trouble free motoring. I ascertained that the whole units were 26 model units, so were probably replaced before I bought the car.
About 12 years ago I took them out again and completely rebuilt them myself. I made brass bushes for the main spindle. I put "speedy sleeves" over the shaft where the seal sits. Speedy sleeves are a thin stainless steel ring (about 5 thousands of an inch thick) and are available from bearing suppliers. I also changed the sealing system from the original stuffing gland arrangement. I filled the gland seat flat and used a quad seal together with half an O ring which I very carefully ground in half on the side of the stone wheel on my bench grinder. The O ring spreads the quad seal for continuous sealing. I replaced the radius arms with new units that I bought on Ebay. I used hydraulic jack oil in one unit and ATM in the other to see if there was any differences, there weren't. I've now done another 25,000 miles and bar an occassional topping up have had no trouble. I've also heard of liguid teflon being used as a seal in the units, but don't know anything about it.
The total cost was less tha $100 US
One problem I have encountered is the front cross member sagging in the middle to the point where my steering cross link started rubbing through the sump. I fixed this by placing 1/8" thick washers under the front engine mounts and brassed up the wear in the sump. Next overhaul I'll get the crossmember re-bent back to original. I also noticed that some of the crossmember rivets have come loose. The 34 has done about 110,000 miles, about 70,000 by me. I get about 35,000 miles on the front tyres and they wear pretty evenly
Chris

The "sagging cross member" was rather common on these when they were used on rough roads for many thousands of miles.The cross member was "improved" in 1935 with heaiver gauge steel and a deeper channel section.The outter ends at the king pin supports were also "improved".....It was easy to spot the ones with the sagging cross member as the front wheel camber was visibly way off.The cars driven on paved roads seldom had a problem.

I have a knee-action unit for sale from a 1937. Has 46000 miles on it. I can send pictures. Thanks.

care needs to be taken when replacing the king pins on the knees the thrust bearings are in a differant place compared to a soid axel . see repair manual . if the bearings are put in the wrong place the tie rod wears a hole in the pan . i had this to happen as i bought a car with this problem and after trying to figure out why the pan had been welded so many times i got the book out . i cant figure out the speedy sleeves repair as the out side of the shaft wears as the bearings crumble the splines in the center of the shaft is the same size as the bearing id the only way we are able to repair this is to metalize the shaft and regrind the shaft to standard size replace the bearings with bushings keep oil in them and they last a while

Pushrod
The speedy sleeves are about 5 thou inch thick, if the wear is more than this it can be be built up with a liquid Locktite product, put the speedy sleeves on while it is still wet, it sets hard and works really well. The first time I used the speedy sleeves I didn't use the Locktite and when I redid them later I found the shaft had some wear under the sleeves, I was told that this happens due to heat transferring through the stainless steel. The Locktite product stops this heat transfer as well. It will build up to 15th inch according to the specifications
Chris

chevguroo the speedy sleeves we have used are the sweat on type works real good on grooved seal areas like crankshafts but if i understand you are using it on the bearing area which is the part of the shaft that we have had the most problem as the needle bearings break and work on the shaft this area of the shaft is the same od as the splines and we cant undercut and sweat a sleeve i am a locktite fan real good product but i dont think a .005 sleeve would hold up in the heavy bearing area even with locktite . seal area yes

pushrod
I have done over 20,000 miles since putting in the speedy sleeves and don't seem to have any problems. Last year I did 3,500 miles over 3 weeks and there were no problems. I have brass bushes in mine, I made these myself. The spindles were not a good idea as they only rotate back and forth a little as the arm goes up and down, and spindles were meant to rotate. When I bought my 50,000 mile one owner car 31 years ago it already had brass bushes fitted, in fact I'm pretty sure that my knees are 36 and I believe that from 36 on they used bushes in lieu of spindles.
My shafts had gooves in them caused from wear in the bushes and the grooves in the shaft were caused by the shaft rubbing up against the large adjustment nut. I filled the grooves with the locktite and then just slipped on the speedy sleeves with the tool provided in the kit.
Chris