Hello. I'm new and looking to learn as much as I can

[ryanbock]

I just recently acquired a 1964 gm 4106.  It was passed down to me and my grandfather originally converted the bus in the mid 80s. It has a Detroit 8v71 attacked to a spicer 4 speed. The body is in good shape and the interior needs brought up to date. My goal with this project is the use this to replace my 40 foot living quarters race trailer. I have a off-road truck that fits in the back of that. I am wondering the following things.
What is a good automatic transmission upgrade?
The blower is bad and I am wondering if it would be a better idea to just swap the engine for something a little more modern
What is a good way to bring the steering up to date and make it safer
What is the tow rating for a bus like this. I need the ability to tow 10k
What are common issues for this bus
What are the common maintenance items.
What is a good engine to put in there.

My goal is to have a reliable rig that I can tow with and have no problems traveling across country. I do have decent mechanical knowledge and fabrication skills as well. I would like to thank everyone in advance for thier help.

[ryanbock]

Also are there any good shops in the Bay Area that could work on this bus?

[windtrader]

Welcome Ryan,

I'm a noobie looking for my first coach. Others will surely chime in too but a GM 4106 should have the tow attachments upgraded to take a 10k load, primarily those coaches have insufficient bracing to take much vertical load.

In general, these old coaches are both commercial and old, so some parts require some searching and are costly. Repowering a bus is pretty expensive, especially if you want a rebuilt motor and auto transmission upgrade; It's going to be north of 20k, far more than the bus is worth. Power steering upgrades are available, generally a Shepard unit is swapped in. Service items are generally similar as cars - motor, transmission, radiator oil/fluid exchange. Just remember these hold many gallons of fluids, not quarts. To have it reliable for coast to coast trips you are looking at a lot of money if the coach has much deferred maintenance. Good luck, Don

There is a place up in Williams, Ca., run by Ted Campbell. He is one of the most regarded bus mechanics in NorCal.

[RJ]

Ryan -

Welcome to the madness!  This site has a ton of information, lots of your questions can be answered by using the Search box right up here. ^^^

So the 4-spd has attacked the engine, eh?  (Just kidding, I knew you meant attached. . . )  So let me answer your questions:

1) You only have one choice for an automatic upgrade, an Allison V-730.  It's a three-speed unit that feels like 4 due to the lock-up torque converter.

2) Your engine is a LH rotation due to it's V-drive configuration, thus the opposite of every other bus on the road.  If you swap in a Cummins, for example, you'd have four speeds in reverse and one going forward.  The most common powertrain swap is for a 6V92T /V-730 out of a transit bus.  The 6V92 can easily be pumped up to 350 hp with a turbo and injector change - no cam timing change needed.  (OTOH, if you want to spend the $$$, you can rebuild the 8V71 into an 8V71T (turbo) pumping out 375 or 400 hp, but you're looking at $30K+ for that.)  Sadly, there are no modern 4-stroke engines that will work in your 4106, due to the rotational issue.

3) Best way to upgrade the steering is to find a 1975 or later GMC 4905 and pull both the steering box off the axle plus the box at the bottom of the steering column.  This is the Sheppard system, which, when properly installed, gives you fingertip steering.  You need that steering column box because the ratio is 1:1 vs the 4106's 1.5:1.

4) The 4106 will easily tow the 10K trailer and you'll hardly know it's back there IF you use a TrailerToad to handle the tongue weight.  The entire engine cradle hangs from the roof with two bolts, and a heavy tongue load can, over time, either wear through the bolts, or stress the roof to the point the whole back end sags from the rear axle back.  It's not so much the static load, but the instantaneous dynamic loads induced on the hitch that take their toll.  OTOH, a TrailerToad takes that load, creating a situation virtually the same as flat-towing a car.  www.trailertoad.com

5) Common issues - Cracked engine bulkhead from overloaded tongue loads on the trailer hitch.  Rear window glass is now made from unobtainium, and the company that used to manufacture replacement rear caps is no longer doing so (and has destroyed the molds).  Clutch parts are expensive, and it's easy to smoke one attempting to start on a hill w/o the correct technique.  It's extremely rare to overheat an '06 if the cooling system is in good condition - 90% of the time, overheating can be traced to "operator error."  OEM rear clearance lights are in the same part availability situation as the rear window, and forget even attempting to find NOS front turn signal lenses.  Since the chassis is predominately aluminum, the only rust issues are usually around the front and rear caps and framing around the driver's side window.  The body is anodized aluminum, originally with a satin finish.  Because of it's age, the finish nowadays often is somewhat dull or streaked.  Several busnuts have had good luck with "Wipe New" (found in the automotive section of WalMart and others), and some decide to go crazy and polish the bus.  Doing so, however, destroys the protective anodization, thus dooming the owner to constant polishing to stay ahead of the oxidation that starts taking place as soon as it's polished.  Others simply paint the bus. . .  Another issue is finding a competent technician that's skilled on the two-stroke Detroit - most are now retired.

6) Common maintenance items: Complete lubrication of the chassis - especially the drive shaft u-joints.  Using the correct engine oils (more about that in a moment), tires, air bellows, batteries - basic normal automotive-type items, except on a bigger scale.  However, most major repairs, such as the installation of new air bellows, will only have to be done once over the average coach's RV life.  Thus, if you do a LOT of preventative chassis maintenance early in your ownership, the coach will return many years of faithful service with simple routine service.

Now, engine oil.  This topic has been beaten to death over and over again.  Bottom line - DO NOT USE MULTI-WEIGHT OIL IN A TWO-STROKE DETROIT DIESEL!  Even if it's Amsoil's "supposedly approved" synthetic HD Diesel 20-50wt.  Detroit recommends straight 40wt for 90% of operating conditions.  Mobile Delvac 1240, Chevron Delo 100, and Shell Rotella T are the three most popular brands, but there are others that meet their specs.  (Rotella barely meets the specs due to it's higher sulfated ash content.)  Here's a link to the current manufacturer's oil recommendations, info on the two-strokes begins on page 20:

https://www.mtu-online.com/fileadmin/fm-dam/mtu-global/technical-info/fluids_and_lubricants_specifications/neu_01_04_2015/A001061_36E.pdf

Be aware that this oil is normally not found on the shelf at Wally World, it often has to be ordered.  O'Reilly's can usually get Delo 100 overnight, or within a couple of days.  I just picked up eight gallons of Delvac 1240 from my local Mobile distributor, they transferred it in from another branch overnight, but they usually have it in stock. (And it was actually a couple of bucks/gallon cheaper than Delo.)  Here's a link to Mobile's dealer locator:

https://mobildelvac.com/en/distributor-locator

I don't use Rotella, but Shell has a dealer locator also, if you're inclined to use that company's product (which, btw, is now 100% owned by Saudi Arabia.)

7)  I addressed "what engine to put in there" briefly above.  If you really want to do an engine swap, you should consider selling the 4106 and buying a "T-Drive" rig like an Eagle, MCI, or Prevost.  Most of these brands can easily be retrofitted with modern 4-strokes, the most popular being Detroit Series 60s and Cummins ISMs.  If you decide to go this route, 1985 or newer is what to look for, as that's when the industry went to 102" wide chassis.  That extra 6" of width makes a BIG difference inside!

  Put this phone number in your phone (or memorize it) - 1-888-262-2434.  That's the number for Luke at US Coach in NJ.  Luke's probably forgotten more about GM buses than most of us combined.  Strong supporter of this crazy hobby, ships parts the same day (if in stock) when you use plastic money, prices are fair and competitive (with far better knowledge supporting the pricing than lots of vendors), normally knows the exact parts needed when you call, and is a great guy, too!  His brother, Bill, runs the shop.  Support those who support us!!

A little closer to home it Ted Campbell's Coach Maintenance in Williams, CA, right off the Husted Rd exit on I-5.  Like Luke, an excellent source of used GM parts, and is affectionately known as "The Master" by fellow GM Coach owners.  Just don't try to contact him before 4:30 pm, as he works nights.

The 4106 is often referred to as the "Sports Car of Buses" due to it's good handling and decent power/weight ratio.  It was a tremendous coach in it's day, but because the industry was quickly going to 40-foot models, that sealed it's doom.  With proper maintenance, they will outlive you.  I would have bought one myself, but the one I was most interested in has never been for sale (even tho I called the owner every six months or so over a 10 year period!)  I ended up buying an MCI MC-5C that was converted on a brand new shell by Angola Coach.

FWIW & HTH. . .



PS:  Please take a minute to update your forum profile to one similar to mine below.  This will help us help you even better, and you might even discover that there's another busnut nearby!  Simply click on the "profile" tab above.  When the new page opens, click on the "Forum Profile" option in the LH menu and follow the prompts.  At least your first name, your home/base city/state, and coach make, model, and powertrain will be appreciated.  If you want to include the VIN (PD4106-XXXX) you can - another '06 owner may turn up with a sister coach!

[ryanbock]

Wow. This has already helped a lot. Is there a way people have braced the back end to get a higher load rating?
Is the v730 a direct bolt up. (Minus the shifter)
Thanks windtrader and rj

[Beesme]

You can install a series 50 4 stroke . Just sayin . For 15k a shop in pa will do complete job . I almost pulled the trigger last year on my 4106 . But a Newell came along and I bought that instead and kept the 8-71

[Beesme]

Oh sorry but I meant to say out of a 90s era rts

[Detroitenginespecialist]

Ryan,

If you need anything Detroit Diesel 2 cycle related, please give us a call at American Fleet.  We only build Detroit engines for the bus industry.

[Geoff]

Oh sorry but I meant to say out of a 90s era rts

Why pull the engine/transmission out of an RTS when the RTS is a better bus than a 4106?  It comes in either 35 or 40 ft, and 96 or 102 inches wide.  It already has Sheppard steering, and the rear cradle is much stouter than the 4106.  I have an '82 40'er, 102" wide, with a 350 HP 6V92TA.  I have pulled over 10k trailers​ with way over 1,000 lbs. of tongue weight.  A very nice coach to drive.

BUT, the market is full of already converted buses for sale that would meet your needs.  My advice is to buy an already converted modern bus and sell the 4106.  You will be 💰 ahead.

--Geoff

[TomC]

I would highly recommend you change to an Allison V730. I have 4.56 rears and with 11R-24.5 I cruise at 1900rpm at 60mph. 4.11 is the highest available which will get you 1720 at 60 mph (V730 has a .88 overdrive 3rd).
V730 is also available with a reverser gear on the input shaft so you can run a normal right handed rotation engine. Some of the 4 stroke engines that have been used is the Detroit Series 50, Cummins ISC, ISL, ISM in both Diesel and Natural Gas.
Switching from the V drive to a straight T drive would require about a 2ft extension on the back. There is a 4104 that had that done and unless you really look at it, can't really tell the difference.
I also have a V drive. The main reason for the V drive was maintenance. The complete engine/transmission was mounted on a cradle that can be removed by one person in about 2 hours that is held in with 4 big bolts. A bus could come in with a blown engine and the night crew (2 men) could remove and install another power plant in under 8 hours so the bus was available the next day. Good Luck, TomC

[Geoff]

moved

[Dave5Cs]

OIL Info for anyone who doesn't know.
O Reilly's will match any price you can prove on oil. Delo 100 had gone up to 20.99 a gallon and was 13.99 last year.

I got Rotella T-1 from Amazon Prime free shipping for 18.99 a gallon last week.

I told the O Reilly's guy about it and he said next time just bring me the price print out and He will match it.

[RJ]

Ryan -

Thanks for updating your profile - I know of at least four other 4106 owners in the Bay Area, so you're not alone!

It was late when I wrote that missive last night, so I forgot about the Series 50/VR730 powertrain package.  It uses a reversing gear in the transmission to change the RH engine to LH transmission input.  Finding one, however, might be an interesting challenge.

Don't know if you're on Facebook, but there's a 4106 group there that you might be interested in.

FWIW & HTH. . .

[Geoff]

RJ--

You should save your great (and long) posts in a Word document.  That is a lot of energy spent writing your very good long posts more than once.  I wish I would have done that years ago.  Now I have the tendency to be short.

--Geoff