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Weird predicament

So I Have a 86 F-150 and it has a motor and transmission from a 79 F250. I'm having difficulties locating a driveshaft that will fit. I bought the truck as a roller and I'm building it. I have to replace the transmission but that won't change the length of the driveshaft needed. I measured and it looks to be a 64" distance. I can't find any that long. Suggestions?


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Fellro

Moderator
Staff member
So what engine transmission is it? For the most part, the length shouldn't be an issue unless it is also a transmission that didn't get used in the 86. Otherwise your other option is to have one made, which actually isn't as expensive as you would likely think. Find a driveline shop in your area and they can tell you what you need to do.
 
im with fellro
i had drive lines front and back built for my 77 (new joints, new slip yoke etc) 435 for both shafts and parts. well worth it

just take measurements with the truck on the ground. u joint cap center to u joint cap center
 

Fellro

Moderator
Staff member
Shop near here is considerably less... We built a heavier duty driveline for the F350 Cummins for about that. That was on a crew cab, so 2 piece driveline, from the trans to the rear axle all beefed up and heavy flange at the axle.
 
Sometimes if you find a shaft that is too long the price to shorten the shaft is very minimal, had one shortened before for $100 bucks and balanced.
 

Fellro

Moderator
Staff member
That is also true, as they only replace one end after cutting the tube down.
 
Alright, The motor, transmission, and Transfer Case are from a 1979 f-250. They got retrofitted into an 86 f-150.
 

Fellro

Moderator
Staff member
So the listed options for the available options from a 1979 F250 are 300 inline 6, 302,351W, 351M, 400, and 460. However, if factory original, it gets narrowed down by the 4WD part to 300 and 400. However, there still is the manual vs auto part of the transmission to also deal with. F150's came factory with 300's as well.

So do you see why we are asking WHICH motor and WHICH transmission it is? Anything we say is a guess, and could be the wrong one. Length of the driveshaft is one consideration, another is which yoke goes in the transmission if it has a slip or fixed, then if fixed it needs a driveshaft with a slip joint in it.

When taking on a "retrofit" these are things that you must be able to answer at least a little, or show us what you have so we can help you identify it. Giving the year it came from helps me almost as much as telling me the color of it. (I actually did have customers that could not tell me the year, make model, but could tell me what color it is, so an old parts counter joke...)
 
sorry, I thought I said what the motor and trans was in original post. The truck originally had the 351c and a 4 speed manual. Now it has the 351m with a C6 transmission. its an 86 F1-50 Single Cab long bed.
 

Fellro

Moderator
Staff member
It would originally have a 351W, C's never came factory in a truck, and certainly not that new of one. Trick to it all is, how did they position the motor/trans combo. Is the F150 also 4WD? How does the front driveshaft fit if it is? I am trying to get a good feel for what you have vs what it was so it may be of help. Is the fan blade fairly close to the radiator or no? The last year for a 400, which is very similar to your 351M was 1982, but in a 250. So it still is a strong possibility you will not find a stock bolt in solution.
 
See that's just it, the Truck didn't have driveshafts when I got it. I'm working with measurements. As far as the fan blade goes, its got some space, enough to fit a boot in between them sideways. but the fan blade is also slightly offset.
 

Fellro

Moderator
Staff member
Well, I can get front shaft measurement from a 78 I have, which is the 351M and C6. Rear won't help for a number of reasons, number one being it is a short bed. Trick of course is if the same relations are in the 86. Also have an 88 150 4WD, but is a 5 speed, so can be different. Guess run some tape and do some comparisons...
 
Which I had a measurement but haven't been able to find one online in that size.
 

Fellro

Moderator
Staff member
Does the cross member appear to be in the original location? Also, need to identify the transfer case, as well as the rear axle.

Check this out for transfer case: http://www.blueovaltrucks.com/tech/transfer_cases.htm

Rear axle likely is a fixed differential, in that you have to remove the diff fromt he axle housing separate from the pinion, while a removable is a 9", the differential comes out the front of the axle housing.

What I am seeing so far is that the combo of the transfer case output and the rear axle are not likely to play nice. Back to custom shaft.. Might be necessary just to get the right u-joint cap sizes.
 

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