The Stovebolt Site Forums The Shop Area Engine Shop Alternatives to $1000 Trany Rebuild?

My 4 speed selective syncromesh trany on my 1959 3800 Chevy Apache grinds when shifting from 2nd to 3rd and up to 4th unless I hold the clutch in and coast for a long time.

As you can imagine keeping momentum to shift up but allow enough time to shift without grinding is bothersome and can be quite difficult starting from stoplights on hills.

Trany mechanic diagnosed it as missing some syncronizers and possible worn bearings. He quoted $800 to $1000 to put in new syncronizers, bearings and gasket kit.

Sounds like he's basically rebuilding the transmission to me.

For you old hands with these classics, does this sound necessary or a waste of money?

My second question is on the "fastest speed" I can drive her without damaging the engine or trany. She seams to cruise pretty well at 60 MPH with the bad trany as it is, however she has that low grany grear (1st) and from what I've read about earlier trucks on this site raises questions whether I should be pushing her past 45 MPH.

Should I also be looking at an overdrive or ring and pinion swap with the transmission repair? Or is a '59 trany and 283 v8 more capable of higher speeds than the '50 216?

I'd deeply appreciate any replies or inquiries to help get the old girl back where she belongs.

Sincerely,
Jacob Marshall

Welcome to the Stovebolt!

I don't recognize your description of the transmission, but assume its the same SM420 4-speed commonly found in Chevy/GMC trucks up through 1967.

If that's the case you should be able to buy another one for far less than rebuilding your existing one. They are pretty durable and lots of buys take them out to replace with automatics, so it shouldn't be too hard to find a good one.

i distinctly remember pushing a broken-down car down I-30 at 75 mph in my dad's 65 chevy 4x4 with the granny low 4 speed and 283 v8. It was loud as all get out, and sometimes felt like you were on an out of control carnival ride, but you could tell the drivetrain wasn't even trying and that it would give you at least another 15 mph.

Jacob, I'm parting out a 59 model 3800, and it's got a good 4-speed. Drop me an email, and we might be able to do a little horsetrading. We're not supposed to buy and sell on this part of the forum, so let's get this discussion into private territory. My email is in my "profile", just click on my username.

Back when I had that one on the road, it would run 65 or so, with a 235 engine. If you've got the 283, it should go faster than it's safe to drive with the suspension and brakes it's got!
Jerry

Jacob, yeah, these guys are right. SM420's are plentiful if you want to keep stock. Jump on Hotrod's offer.
An overdrive tranny will give you a significant decrease in rpm's however (provided the final drive ratio is around .72 or better - lots had .86 which is not very good).
Your final ratio is 1:1 with your 4 spd. Use this rpm calculator to compare between the 4spd and a O.D. unit. rpm calculator

My 4th gear synchro gear is bad and I double clutch into 4th (instead of coasting). I actually like that because it makes me feel in tune with my '48. If I had to double clutch more than that, it would be a pain in the rear.

My tranny shop said it would cost $200 to fix the 4th gear synchro and $600 to overhaul the whole thing.

Hello, back in the day when I used to blow up things ,I learned that when it grinds going into gear, it means that the syncro ring is bad. The part is about $5.00, and if you simply replace that you should be fine.Now, you can save money by doing some of the work yourself. You can save the cost of removing and replacing the trany=$250.00. The replacement of the syncro ring is where you save as well, another $250.00. If you want to try doing that yourself, you need snapring plyers and greese to hold the needle bearings in place while reinstalling them.If you want to try it,(I suceeded the first time,you could too)it's simply going to take you a few hours ,so set aside a Saturday and go for it.Get a blow up schematic of your trany and a big workbench. Nothing is spring loaded just take it apart slowly and put things in order of removal. I would replace all the syncros .After you have taken everything apart slowly put it back together using the greese to hold the needle bearings in place for reasembly.If you have "ANY" extra parts left over that are not parts you were replacing ,you will have to go back and find out where they go because it just will not work. If you find that you can't do it after disassembly ,simply take it to a trany shop and let them finish.Take a chance and think of it as a learning experiment, try an old trany that isn't worth anything ,they are all basically the same.
Lothar

I forgot to mention, another alternative is try going to the antique car swapmeets, you can usually find good used tranys for $100.00 or less there.I took mine there to sell for $50.00 ,along with the motor ,and rear end and couldn't even seem to sell them at any price so I threw mine into the trunk of an old Honda ,and had the scrap car pick guy come and remove it all for free.
Lothar

Is there oil in that tranny? May have leaked out.A cheap fix that may or may not work; drain the tranny lube, refill with straight grade 50 detergent motor oil, takes about 3 quarts.Modern GL-5 gear lubes can be too slippery for older trannys syncros,and ones with worn parts, to shift smoothly.

Agreed, the lube can cause problems, but I'd be a little spooky about using the 50 weight motor oil. Find a diesel shop or truck stop where they service Fuller Roadranger transmissions, and buy a quantity of "mineral oil" that they use in the Roadranger trannys. it's 85W-140 weight, just like the hypoid lube, but without the super-slippery additives. Hypoid grease in a fuller transmission causes heavy carbon deposits on the synchronizer rings.
Jerry

For a $1000.00 you could buy three trucks equipped with 4 speeds and have parts left over to sell.4 speeds are plentiful and I think they are the same coming from Ford and Dodge trucks too (I may be wrong). I personally would do a poormans overhaul myself. Just replace the bearings and baulk rings unless there's heavy damage like teeth missing.
Just my 2 cents,
Scott

A little historical perspective: SAE 50 engine oil is standard for spicer trannies year round and specified for clark and warner below 32F. 140 gear lube above 32F. Fullers are to use gear lube of varying viscosities (depending on temperature) only, never engine oil. The GMC service manual states that SAE 50 is to be used in the clark 5 speeds and can also be used in the 4 speeds (normal lubricant for the SM420 is 90 gear lube). SAE 50 is equivalent in viscosity to 90 gear lube.

When I opend my first tranny I was scared to death and I was almost sure I never get it back together again.

4 hours and a sixpack later I had new bearings and syncro rings in my old tranny and was driving home.

I can tell you I was proud as hell.

So why let the mechanic have all the fun? Do it your self.

The bearings are around 30$ each, a small parts kit with all the gaskets and rollers and shims and stuff is around 20$ The syncronizers are between 5 and 15$.

Buy the parts, a shop or service manual, chips and a sixpack.

You can do it on a saturday afternoon if you take your time. You spend maybe 100$ (plus the sixpack) and learn while you do it.

Frank

drain your tranny oil replace with 50 per cent 30 wt. and 50 percent stp. it will shift better and your grinding may go away mine did in more than one tranny cheap to

Thank you all for your suggestions and encouragement, and sorry for not responding sooner as I've been away (moving to new location)

I'll do what many of you suggested and re-build the trany myself (just turned 21 so I think I'll forget the six pack I've torn the engine almost to pieces to re-build it and haven't found anything scarry in it (yet) so how much worse could a trany be?.

Again many thanks, you all are a great bunch!

Jacob