Tranny Swap -- '66 Body with '75 Engine
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Tranny Swap -- '66 Body with '75 Engine
I'm new on here and I see there's been a lot of discussion already about tranny swaps, but I'm just looking for some advice on this particular situation: I have a '66 F100, 2WD, that has 300/6 Cyl engine from a '75. Right now it has a 3 spd tranny, and I'm thinking of changing to an automatic because driving it in the city is a pain in the *** (and the arm and foot). My understanding is that a C6 should bolt up to that engine. I have a line on a parts donor, a '73 with a C6. Would that bolt right on there? I'm thinking I should also take at least the cooling lines, kick-down rod and driveshaft. Should I take the column too? Are there any special problems I can anticipate given the tranny is a '73 and the differential a '66? Any advice much appreciated.
Fleet Mechanic
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If the trans is bolted to a 300 six, or a small block V8 it will fit your engine, but if its on a V8, you will need a 300 six flywheel, and use the auto starter. NOt sure the column will interchange, may want to use a floor shift, most standard rear gears are slower than autos, but if both are the same spline, its easy to change third members.
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Thanks very much. So the IL6 will also take the same tranny bell housing as the small block 8, and I use the 8's flywheel and starter also, right? That opens a lot of possibilities for a donor tranny.
Your point about the C4 is also a good one. Maybe I will look around and see if I can come up with one.
By the way, when you say "most standard rear gears are slower than autos, but if both are the same spline, its easy to change third members," what does that mean? What do you mean by "change third members"?
Thanks again
Your point about the C4 is also a good one. Maybe I will look around and see if I can come up with one.
By the way, when you say "most standard rear gears are slower than autos, but if both are the same spline, its easy to change third members," what does that mean? What do you mean by "change third members"?
Thanks again
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From: pahrump nv
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Thanks again. I also wonder about the possibility of just swapping in the whole rear axle. I wonder if the '73 axle would swap into my '66. Could just measure and check I guess.
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From: Sauk City, WI
73 axle will be too wide. 72 was the last year they were the same width as a 66. At least I think thats what NumberDummy reminded me of the last time, heh. 
Any SBF tranny will bolt up to a 300. Id suggest a C4 as well as the C6 is quite a bit bigger and less efficient.
Yes, take the kick down, driveshaft, and possibly the steering column. Im not sure how much of a bolt up the 73 column will be, but it is probably worth having on hand. Im sure someone else has a better line on that swap than me.
I wouldnt bother with taking the old cooler lines as they should probably be replaced anyway. Buy/make a new set of lines, and a new cooler from somewhere like Summit or Jegs and save yourself the hassle of using what is most likely old junk.
Dont sweat the issue with spline count. Just grab the driveshaft from the 73 and if the original doesnt work, take the it and have it modified as needed. You may need to add or subtract length or change the end of the drive draft. This is better left in the hand of a good shop as it requires balancing and welds that will not fail!
Any SBF tranny will bolt up to a 300. Id suggest a C4 as well as the C6 is quite a bit bigger and less efficient.
Yes, take the kick down, driveshaft, and possibly the steering column. Im not sure how much of a bolt up the 73 column will be, but it is probably worth having on hand. Im sure someone else has a better line on that swap than me.
I wouldnt bother with taking the old cooler lines as they should probably be replaced anyway. Buy/make a new set of lines, and a new cooler from somewhere like Summit or Jegs and save yourself the hassle of using what is most likely old junk.
Dont sweat the issue with spline count. Just grab the driveshaft from the 73 and if the original doesnt work, take the it and have it modified as needed. You may need to add or subtract length or change the end of the drive draft. This is better left in the hand of a good shop as it requires balancing and welds that will not fail!
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From: Lost
The 300 uses a nuetral balance flexplate/flywheel, while 302/351W do not, these have a counterwieght on them. Make sure you have the correct flexplate for the 300, or it will shake itself apart, in short order.
Starter is the same 6/V8, but differs between manual/auto.
Starter is the same 6/V8, but differs between manual/auto.
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If I'm right in what you are saying, it makes me wonder -- why would it need a different starter if the flexplate/flywheel is not being changed? I always assumed the different starter was to do with the teeth meshing properly, but if so, and if the same flywheel from the existing 300 is in there, why would it take a different starter? Or am I misunderstanding something? Thanks for your patience, I want to get this right.
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From: Lost
If swapping from manual trans to auto, the flywheel has to be changed. Just make sure the auto flywheel (flexplate) is for a 300. The trans from a 300, 302 or 351W will work, but the flexplate must be for the 300. 300 is internal balance, 302/351W are external balance.
The starter differs between manual trans and auto trans, but 300/302/351W all use the same starter.
The starter differs between manual trans and auto trans, but 300/302/351W all use the same starter.
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OK, so the flywheel on my existing 300 engine, which had the std tranny, had to be replaced by a flywheel for a 300 that has an auto tranny.
The auto tranny itself can be from a 300, 302 or 351W.
The starter can be from a 300, 302 or 351W as long as it's for an automatic.
Yes?
The auto tranny itself can be from a 300, 302 or 351W.
The starter can be from a 300, 302 or 351W as long as it's for an automatic.
Yes?
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