should I change gears or tranny???

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mtandrews

mtandrews

beware the Ides of March
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I just bought a 1987 Dodge 3/4 ton 360/auto Pick em' up literally a few hours ago. Made the transaction, went to the closest gas station (truck was under "E"!!!) and filled up and this S.O.B. took exactly $99.00 to fill up!
Anyway back to the topic. The trans shifts into all 3 gears but it must be low geared as it seems to run out of gear at around 65. Of course it had plenty throttle left but I don't wanna race the engine just to cruise at 70-75 mph. I'll try to find out the rear ratio this weekend but this ain't gonna cut it. Truck runs very good, nice and snappy throttle response too. This truck ain't gonna be hauling any heavy loads, its gonna be a parts chaser that's gonna have to run from San Antonio to Corpus Christi once a week. Will a 518 be useable in this application and if so what years out of what models should I be looking for?
 
You sure your truck is full of fuel? My van did the same thing cut off at $99 exactly, but it was a limit on the card. I took a 20 in The store to finish getting my other 4.5 gallons in there. And proceeded back in for my change.
 
gibson_es said:
You sure your truck is full of fuel? My van did the same thing cut off at $99 exactly, but it was a limit on the card. I took a 20 in The store to finish getting my other 4.5 gallons in there. And proceeded back in for my change.
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maybe so, but I'm cool with that. I wanna figure out this gearing thing...
 
done some digging now that it's light outside. According to a data plate for lack of better words in the glovebox the rear gears are 4.10:1, the tire size is LT235/85R16. I'm quite sure its known that its a Dana 60 being the truck is 3/4 ton. And it's 2WD not 4WD, forgot to add that.
 
I,d change out the 4.10s for some 3.23,s see,n you,ll be doing highway runs.I did this swap last fall in my 73 D.Sport,she,s now a highway girl.On a second not,my truck has 140liter tank(about 35 gallon tank)and gas here is about $6.00 a gallon:angry3:.Consider yourself lucky.LOL.
 
The gears would be a cheaper route to take.

The O.D. trans would be really nice on a few levels except price and labor. You would;
Maintain the current get up and go abilty while increaseing the mileage abilty with the .69 O.D. ratio. 4.10 X's .69 = 282.9.

The earliest 518 trans you can find with the manual switch to turn off the O.D. gear would be best. The actual number/letters of the trans escapes me right now.
 
Labor would be free courtesy of me, I've done O.D. tranny swaps before but on brand X vehicles only, never done a Mopar. Didn't 518's come in Vans or am I tripping??? If I can't find one I guess I'd better follow up on pettybluedarts lead. I did a Dana 60 gear swap about 15 to 20 years ago and from what I do remember it was a friggin' nightmare!!! but I gotta do something...
 
I would go cheaper and just gear it if the trans., etc. seems to be solid. Might be kinda difficult to find the ratio you want if doing the junkyard crawl since most D60's seem to come with the 4.?? gears for towing. New of course you have tons of options.
The trans. would be the best overall. I would just pick up an early one, throw a rebuild at it and toss it in there. Just don't forget about all the other B.S. you're going to need with it. I think they came out about '90 in all the full size vehicles.
 
One of the tire charts shows this tire is 31.7" tall, with 4:10s should give you 3042 RPM at 70 MPH

Now that is almost EXACTLY the same RPM my old 70 RR ran, and it would get just under 14 mpg with the sixpack engine (headers, Holley 800) and later would just nudge over 17 - 17.5 with a 340 in the car (headers, Thermojunk/ Quadrajet)

I won't dispute that an overdrive/ gear change may help, but if this thing is carrying a lot of cargo on these trips, too much OD may hurt as much as it helps, IE very little or no gain due to weight of cargo versus drop in RPM.
 
won't be carrying much in the way of cargo, 700 to 900 pounds at the most. The most ever carried by its predecessor was tow GM V-6 engines with the trannys still hooked up to them out of UPS package cars, and that was a one time deal. I wanted another 1/2 ton like my insurance totaled out but either they were junked out or had a bazillion miles on them and poorly maintained. Sure I could pull the powerplant and redo it but I needed one ready to go out of the gate. If I decide to go gears I'd go NIB. I just don't want to buzz that 360 at 3042 RPM on a 300 mile round trip once and sometimes twice a week plus local driving...
 
Yea, vans and trucks, Durango's and Dakota's w/360's have them, HD units are a best bet target as 1500 or light trucks may not/probably not have them. But check anyway. Same oil pan as the older 904 or 727 differences still apply. Look for that familur 727 pan on the OD unit and yor good to go.

The trans mount is different, so grab that for possible use/re-working of it. Shorter driveshaft and possible pinion angle adjustment. That's all I can think of at the moment.
 
mtandrews said:
don't want to buzz that 360 at 3042 RPM
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3K is hardly buzzing an engine, it's the reason I posted my old car as an example. It had 3.54's. My buddies brand new 70 3/4T 4x4 Chevy at the time had 4:10's in it and both his and my vehicle were so close in RPM at speed that you could hear the "beat note" between the two engines.

Lots and lots of vehicles were geared at that level with no ill effects.
 
You are correct, the only "ill" effect IMO is higher fuel consumption and engine wear. My Dusted has 3.91's in it but its not a road car so I'm fine with that. My daily driver has OD and is better suited for what I use it for. I fully understand what you're getting at and I like your viewpoints. If I can score a 518 I'll go that route but if I don't find one in a reasonable amount of time I'll do the gear swap.
 
I forgot to mention, any chance you can just up the tire size somewhat?
 
Trans, find an OD. If you can do the change and find the trans. The low gears plus the OD will be a treat to drive. Nice easy and torquey take off and still good fuel economy. The nice thing about a low gear is on a heavy vehicle you get an easy throttle peppy take off that burns less gas, then if you have OD, you get the gas mileage on the top end. Plus if you neeeed the low gear, just turn off the OD and whammo, low geared truck. A tall gear on a truck is totally depressing. It labors to get thru 1st and burns a fifth of gas just in first gear as it boggs its way up to speed. Only my opinion.
 
Well YEAH but still cheaper than a trans/ gear change.
 
The trans. swap is the most work and most expensive but will by far yield the best results. If you go the route of swapping gears you really don't want gears taller than 3.54's and it still have decent take off with a load. The A518 came out in 91 if I remember right and in 96 it went to full electronic shift so you need one made between 91 and 95 or you'll have to wire in a trans. computer to make it work. The only big problem going with a A518 is the cost. You'll probably be lucky to buy one, rebuild it and install it for under a grand. If you plan on doing a lot of driving you'll save it in fuel but if you only drive it once in a while it'll take quite a while to even get your $1000 back.
 
mtandrews said:
done some digging now that it's light outside. According to a data plate for lack of better words in the glovebox the rear gears are 4.10:1, the tire size is LT235/85R16. I'm quite sure its known that its a Dana 60 being the truck is 3/4 ton. And it's 2WD not 4WD, forgot to add that.
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67Dart273 said:
I forgot to mention, any chance you can just up the tire size somewhat?
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235-85-16 is really about as tall as he can go without going to a more agressive tread. to go taller, he would be pretty limited to 32's and bigger as far as availability is concerned. They make them. Theyre just hard as hell to find.
 
With those huge tires I would keep the gears and go for a trans with OD.

I installed 4.56 gears over the 3.55 gears that was in my 03 Dodge Ram with 22" wheels. I of course have a OD transmission. This was a big thing on the Dodge Truck forum I used to frequent. I believe Dodge got the word their trucks come with 4.56.... what I've been told anyways.

You might want to check this site out.... http://www.fortrucksonly.com/

I and some of the members been hanging out over there.
 
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