toploader interchange
- Thread starter flexiclese
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RogerC62
Founding Member
I don't think the 385 big block toploader is interchangeable with the FE big block toploader. I believe the input shaft is larger on the 426/460 version. I seem to remember reading that somewhere. I'm sure you can verify it somewhere on the net but I can't think of the site right now.
you can but the input shaft on the FE top loader is shorter than the 429/460-small block top loader trans. the daytona top loaders did have a larger diameter input shaft, but they were installed on the boss 429 and the scj 429. the others got the smaller input shaft.
All the Toploaders used the same bolt pattern and two input sizes (1-1/6" x 10 spline or 1-3/8" x 10 spline) the thing to watch for is the two different input shaft lengths, the big block 1-3/8" and 390 specific Toploader use the shorter input , the front portion forward of the splines is shorter by about 1/2" to 5/8". The 390 Toploaders had the smaller diameter input and short front snout. As far as I know all the large input big block Toploaders also had the short front snout. The splined portion is the same for all.
dennis112
15 Year Member
There are actually 2 possible bolt patterns for the toploader. The early 64-65' bellhousing had holes spaced closer than the later models, and the toploader was built to match with short mounting ears. Late 65' and newer toploaders have both the original narrow pattern plus the more common wide bolt pattern.
Here is an example of both patterns on a newer toploader:
Here is an example of the 2 driveshaft lengths:
View attachment 383496
Here is an example of both patterns on a newer toploader:
Here is an example of the 2 driveshaft lengths:
View attachment 383496
So if I understand you correctly a '67-73 427/428 toploader will bolt up behind a 69-73 429/460 bellhousing? The input shaft splines, diameter and length will all work together. But a 390 may not?
Thanks for all your replies.
dennis112
15 Year Member
That is correct as long as your new input shaft matches the gear ratio of the tranny--(either 2.78 or 2.32.) These 2 type of input shafts have different # of gear teeth.
Dennis is correct,
I didn't include the earlier bolt pattern cause there's not that many in circulation. Swapping the input may also wind up with gear noise from different wear patterns between the gears. I had one Toploader built with parts from three and while they had the correct ratio gears, the wear was different and I ended up with a transmission that made an excellant imitation of a roots blower when driven.
I didn't include the earlier bolt pattern cause there's not that many in circulation. Swapping the input may also wind up with gear noise from different wear patterns between the gears. I had one Toploader built with parts from three and while they had the correct ratio gears, the wear was different and I ended up with a transmission that made an excellant imitation of a roots blower when driven.Yea, that's correct. Just watch the input lengths and make sure the front snout goes into the pilot bearing when it's all bolted together.
The 390 Toploaders will also bolt up to the other bells, the input shaft is just a smaller diameter, you'd need a small block type clutch for it but with a diameter to match the flywheel. The GT390's used a 11 or 11.5 clutch disc with the smaller input shaft splined center.
This does actually work but I wouldn't trust anyone to do it unless they had a great reputation.
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