moparerrnocar

Hey guys, newby here lol... I know you guys know more abought the 727/518/618/46/47/48 than most of the gasser guys since you guys put out insane amounts of torque. So I'm here for some tranny help

I got an 86 gasser W150 that I'd like to swap to O/D and rebuild/upgrade the tranny to handle 550hp/600tq(408 stroker). I have quite few questions, some of which you might not be able to answer since its a gasser and all, but any tips or advice that you might have, please share. I'll get to the hp goodies later. But first,..

What years can I swap from? What year would you suggest and why? What years had a 3pin lock-up? My 208 wont marry correct? What options do I have other than the 248, how does it compare to the 208 in strength?

Thanks

JD730

Most of the internal hard parts will swap. Drums, planet carriers, etc.... There might be some differences on the input shaft and the support retainer. The pumps are definitely different, diesel pumps are much bigger displacement wise.

The front main case is the primary difference in the gas vs diesel trans.

The overdrive sections are identical outside, but internals and clutch counts are different. There are two basic overdrives, the early ones with the hydraulic governors used in the A518/A618/46RH/47RH transmissions. Any transfer case from a 727 can be used with these with no modifications.
The other overdrive section is the the electronic controlled transmissions, 46RE/47RE/48RE. The OD is shorter, than the RH type and a transfer case from a 727 will need a spacer to work with this OD section, how thick I'm not sure.

Are you planning on having automatic shifting or a full manual valve body? Reason I ask is it will open up other options for overdrive section parts and what years to scavange parts from. A 47RE would have most of the good internals you're after. Lockup converter for your gas engine?

The gas transmissions have the same short comings the diesels have. Internal leaks are the death of them. Overall endplay is very important. Alot of shops don't take the time to set the OD sims (there's two places they are set, one i easy and the other is forgotten about) up properly and end up with excessive endplay and an internal leak that wipes out a clutch in a short time.

moparerrnocar

I wont be swapping any parts from a 727 or an RE. I should have been more specific. What was the last year/model to offer an RH for gas? Not sure which year/package came with lock up either. Really, I was told my 208 wont work, but I'll have to look into that latter. This will be just a factory v-body with TG shift kit. Will I still be able to drop gears at any speed like I can with my stock 727? From now I'll just ask you guys internal hard part tips/suggestions/mods.

How many discs do you suggest I run, I was gonna run 6 eagles for the forward but not sure whats sufficient for the direct. I can go to 6reds for $100 or 7reds and a new cast drum and piston for $300. Should the condition of my drum be the deciding factor there? For the o/d, I'm not sure how many clutches there is, theres alot. I was just going to run reds in the o/d with the addition of a 1000lb spring.

For planet sets, people tell me the steal 4pin is stronger than the 6pin aluminum because the splines are the weak point. To be honest I'm not sure what the 4x4 gas 518 came with for pin count, I wana say 4pin in both direct/forward. What would you suggest 4pin steal or 6pin alum? Is that in both or just direct?

Sprag, I know they updated to a 14 roller in 92. Is that adaptable in the pre 92? How much stronger is the 14 to a 12 if they're both a super duper 6 bolt race(whatever they call it lol)? Is a bolt in sprag worth it for preventative disaster or are they more for repairing a stripped case. All I know is if it lets go in 1st it'll Spin the shaft 2x the rpm of the motor and explodes the cast drum .say bye bye to trany and your right foot.... What else causes sprag failures

For bands, I'm not sure how wide I can go. Should both d/f band be rigids? How many grooves? What material? What ratio? I already plan to upgrade the strut and anchor but is that for both or just direct?

The intermediate shaft. The factory revised it for improved oiling. What year was it revised and what did they change? Is it something the average joe can do? Any mods to the case that should be made in conjunction with the shaft? Whats the hp/tq limit of the shaft? Any difference in strength after mods?

I know, its a lot of q's... I do sincerely appreciate the help

JD730

I'll tell you what I run and exactly what I built first.
In my 93, which at one time was 424hp with 1039 ft-lbs of torque, right now its turned down, somewhere around 360hp and high 800's for tq. The trans thats in it only has 30,000 miles on it, but they are probably the hardest you can put on a trans. Truck pulling, drag racing and trailer towing.

I had put a 47RH in it out of a 95 diesel, had it rebuilt by a shop and had nothing but trouble, this prompted me to perform my own rebuild.

While that trans was still working I began gathering parts for a 2nd trans. I had on the shelf and 47RE out of a 96 and the A518 out of the 93. I started looking and determined that I could make a 47RH by using the 47RE front section and putting the A518 output shaft and tail housing on the newer/better/less worn overdrive hard parts from the RE section.

Just for clarification the difference between the diesel A518 and 47RH/E front cases are the rear band area, the 47's have a much stronger anchor point and use a double wrap vs the single wrap on the A518. To further confuse you a diesel A518 may be made lockup by using the lockup input and front support with the proper valvebody along with the correct converter and engine adaptor. And the 47 may be made non-lockup doing a similar part swap. I know this works with the diesels, it should be similar with a gas trans.

Ok, back to what I did on mine. I tore down two complete transmissions, used parts from the 47 and 518.
From the 47 I used all the hard parts in that section with the exception of the input shaft, I decided to install a billet one. The 47 hard parts included a stock 5 pinion steel front planet carrier and the stock 5 pinion aluminum rear planet carrier, sun gear, shell, intermediate shaft, front drum ect... I installed new thrust washers and anything that I thought should be replaced.
To make the trans an RH I removed the stock overdrive piston retainer and installed an aftermarket one that had the governor ports coming through it. I could have used the one from the A518, but I decided not to. This is the first thing that goes into the trans, the aftermarket retainer also has instructions on drilling a small hole from the trans cooler return passage into the sprag area for extra oiling. I also replaced both front and rear servos with improved aftermarket designs to correct some of their short comings.

Onto the assembly, new seals or gaskets all around of course, I'm going to go in order of assembly, I reused the rear band, it looked like new. The forward clutch, which is the rear most clutch in the front case, is stock borg warner clutchs and stock count which is 4 discs. The front clutch is also stock type with stock count, again is 4 for that trans. Front or 2nd gear band is also stock type material, it is a flexible band, it is what was recommended by the shop that I got the converter and valve body from. The front lever is the stock 3.8 ratio, but it is a billet lever. It is important for shift timing and it is important for the apply force on the band. When the pressure is increased, mine starts around 90 and goes up to 150psi on the accumulator port in drive, the apply force is also increased, so sometimes it isn't necessary to use a 4.0 or 5.0 ratio apply lever, you will need to do some of your own research on this.

The overdrive section is completely stock, the only thing I did was take the guts from the RE section, remove the output shaft, reinstall the 518 output shaft, new thrust bearings, ect... reassemble the whole thing with a new spring and reinstall in the 518 tail housing. I don't know how this applies to the gas world of transmissions, but there are 3 different gear set angles on the diesels. Straight, 23* and 15*, most people that know anything about them will recommend not using the 23* gear sets.

I feel like I'm writing a book, I'll try to pick at some of your questions later today if someone else doesn't answer them first. Here's some more light reading from some other posts on this site if you haven't found them already.

https://www.dieseltruckresource.com/...d.php?t=160276

https://www.dieseltruckresource.com/....php?p=1991156